Repairing Audio Video Electronic Devices / Components:
How Do You Fix it When it Breaks?
You've been enjoying your entertainment setup for years! You've shown it off for your friends and family (yes, probably each and every time they've come to visit with you). It has faithfully served up movie after movie, song after song. But today is different. You are part way through your latest movie and the screen does dark or the audio just completely dies. You hit the Power button and nothing happens. In a panic you shut everything down and power it all back up again. Only that one device refuses to come back on. For me, this has happened to a number of very expensive black boxes around my home. My Yamaha Clavinova CVP-85A digital piano, my Mitsubishi 65" high definition rear projection television set, two different Marantz pre-amplifiers, and one power filter. Each of these devices (with the exception of the power filter) had an original retail price that was in excess of $2000. While I purchased many of these items for significantly less than retail prices, the prospect of replacing them is not attractive at all. For most of us, these are somewhat "major" purchases that we research and compare before parting with our hard earned cash. Each offers a warranty, but by the time the device decides that it's had enough, the warranty period is long since over. There are but a few companies that are the exception to this rule. My Panamax power filter came with a lifetime warranty. When mine failed (after 12+ years), I gave them a call. For a nominal shipping fee, I returned the old one and received a new one in the mail within a few days - a class act for sure! Bryston, a high-end audio company located in Canada, warrants their analog audio amplifiers for a period of 20 years! Wow!
The rest of us, though, are faced with a sometimes daunting choice: have the equipment repaired or really bite the bullet and replace it. Many people at this point choose either to go without (even a repair bill can be steep) or to pony up the cash and attempt to replace our beloved black boxes.
I am here to offer you a third alternative: FIX IT YOURSELF! What I present below is certainly not rocket science and is likely to be viewed as nothing beyond the basics to more seasoned service technicians. But, I'd still wager that I can bring 90% of failed consumer grade electronics back to life with the few simple fixes presented below. It's the same story with small engines for your lawnmower, snowblower, or dirt bike: If your engine is approaching 10 years old and you've properly maintained it (regular oil changes, air filters, spark plugs, etc) and won't start, it probably needs new valves and/or a new flywheel key... YouTube is your friend for these fixes.
I know, you don't have any experience. You don't know where to start. What do you look for? And, doesn't this sticker mean I shouldn't be poking around in here?
These are all easy questions to address and just ignore that sticker! It's really meant just to scare you off. Usually, the manufacturer will put a sticker like the one above right on top of the primary screw that holds everything together. That way, there is any easy way to tell if you've voided the warrantee by opening the chassis. If your device is still under warrantee, then don't bother - just take it back for service. But most of the problems happen after that very brief period known as the warantee has expired.
Over the years, my personal experience has revealed a relatively small number of ailments that cause aging electronics to self-destruct. Many of these things simply happen over time and can't really be avoided. Some of these ailments have even been inflicted by us (unknowingly, of course). In many cases, though, repair is fairly simple and straight forward if: 1) you have some experience taking things apart without breaking them in the process, and 2) you have some soldering experience. If you can check both of these boxes, you are in luck. Keep reading... Others should turn back now.
Diagnosing the Problem: Common Symptoms (solutions appear below):
There are relatively few types of problems that cause the early demise of audio electronics (any many other types of electronics as well). Many of these are easy to spot and relatively easy to correct for those that have some experience with a soldering iron.
Problem #1: Channel Imbalances:
As electronics age, you'll sometime notice that something is not quite right with one speaker. Typically, it will sound more loud or more quiet than the other channel. While frustrating, these types of problems often feature straight forward solutions with the application of a bit of systematic exploration.
Problem #2: Intermittent Electrical/Audio Connections:
Has one of the speaker outputs on your amplifier, CD player, or pre-amplifier stopped working? Or does it only work intermittently (moving or tapping on the chassis or wiggling wires in the back causes things to work/not work again?) This has happened to me on two different preamps over the years. Both of which were purchased used on E-Bay and, I suspect, this intermittent problem is the specific reason they were offered for sale on E-Bay at prices significantly lower than new retail. These problems are quite common and have a few primary causes:
Cause #2a: Scratchy / Noisy Volume Controls and Switches. This largely invisible problem (meaning you can't readily discern the problem by looking at things) also has several causes and is the easiest of all problems to fix because it doesn't require any soldering. All you need to do is to remove the cover from your electronics and get a little cleaner into the dirty contacts. This problem happens over time and arises from operating your equipment in an environment that has high humidity, pet hair, cigarette smoke, etc., or just plain cheap manufacturing using poor quality parts. This repair is as easy as it gets!
Cause #2b: An internal wiring connection or switch (a jumper/harness that spans PCBs) has become dirty/tarnished/oxidized. This problem is the same as what I described above, but takes a bit more poking around and sometimes a bit of disassembly of your equipment (removal of circuit boards) in order to address. This, too, is relatively easy and straight forward to address.
Cause #2c: There is a broken solder joint between the printed circuit board (PCB) and the output jack (either an RCA or XLR connection). This happens for several reasons. Perhaps the unit was not properly stored, used, or packaged prior to being shipped to you. In these cases, some sort of physical trauma has inflicted injury on the signal jack and the PCB to which it is attached. Other sources include: the unit was dropped or bumped, the shipping box was dropped, the cables were repeatedly moved and re-installed, the cables were installed and then smashed up against the wall behind the equipment, etc. In most cases, this is a very simple repair as well.
Cause #2d: You use Monster Cables. Another common complaint of equipment malfunction comes from users of Monster Cables. These cable are well known to exert a tighter-than-normal death-grip on the RCA connectors of your gear. In most cases, this is a good thing as it insures that your cables don't work themselves off of the RCA jack, yet ironically, many owners of Monster Cables have reported they rip the RCA connector right from the back of your equipment when you remove the cable. Ooops... Also fixable at home.
Problem #3: Device Won't Power On/Blown Fuses:
So, things have been humming along quite nicely for a long time and all of a sudden, your equipment just shuts down in the middle of your enjoyment. Worse yet, it won't power up again. You're a little smarter than the average bear and you've opened your equipment, found the blown fuse on the power supply circuit board, and have replaced it with a fuse of the same rating (NEVER replace an original fuse with one that has a LARGER current rating!!!). Being all proud of yourself, you put the lid back on the chassis, secure the screws and power it up again only to witness first hand the flash and pop as your new fuse sacrifices itself, saving both you and your gear in the process (See - I told you to replace a fuse only with one of the very same rating!).
Cause #3a: Old/Dead Electrolytic Capacitors: This is most likely the single point of failure behind 90% or more of the dead electronic devices that people discard. An electrolytic capacitor is a component that is used in virtually EVERY single piece of consumer electronics gear. The trouble with them is that they have a clear and definite lifespan (that varies from device to device depending on how/where it is used). Electrolytic caps have a fluid inside of them that is necessary for them to function. As they approach the end of their useful life - usually somewhere in the 10-15 year range - they begin to leak and dry out. They dry out faster if they get hot because of adjacent components, near by heatsinks, living in the desert (yes, I'm talking about people that live in the south western part of the US) or some fool practice like covering vent holes in the chassis or housing your device inside of a cabinet with no free air movement. Once dried out, capacitors fail and usually form a short-circuit. This short circuit disrupts the function of the circuit causing it not to work. If these capacitors happen to part of the power supply for your equipment, they will most likely cause the fuse to blow - repeatedly (which makes it tempting to replace the blown fuse with a larger value fuse - NEVER do this!). This problem, too, is fixable at home, but requires a bit more skill and experience, thought not as much as you might think... If your piece of equipment is more than 10 or 15 years old and has problems, start by replacing ALL of the caps and see how things go from there. This is especially true for electronics that someone has left in the hot attic for the past few years! Before you get too eager with your soldering iron, realize that ALL of the other parts on a circuit board are FAR more stable over time than capacitors. Don't go pulling resistors, transistors, and diodes unless there are clear signs of charred areas on the circuit board indicating that you've had a small fire (see #2b below), DO NOT replace any soldered device on the circuit board BEFORE you have replaced power supply capacitors. Many transistors in older amplifiers are no longer made and ripping one of these out before you've solved other problems is only asking for trouble. It will be harder than you think, perhaps impossible, to find identical replacement parts! CAPS FIRST! They are the Achilles' Heel for all modern electronic devices.
In stubborn cases, dead electrolyitic caps will cause behavioral problems even though the device isn't blowing fuses. If you've replaced all of the caps in your power supply and strange things are still happening, it might be worth replacing ALL of the rest of the caps, especially in "older" electronic devices.
Cause #3b: FIRE! and other Serious Trauma: Now we are into some more serious types of problems and fixes are sometimes a little more difficult. Repairs at this level usually require access to the service manual that was produced by the manufacturer of your equipment. Service manuals are almost impossible to find online for relatively new equipment (especially if the product is still available comercially), though they sometimes become available when that product is discontinued by the manufacturer. E-Bay can be a good source for service manuals, as well as many other places online. Just search for "<insert your model number> service manual" and see what turns up. These manuals always include circuit schematics that are necessary to determine the values of parts that need to be replaced. This is one of the more challenging repairs to do on your own, but one that is still doable.
The above list indicates the most common problems that I have personally come across with my own electronic devices. This list, however, is not all inclusive. A more detailed list of problems and troubleshooting methods can be found on Conrad Hoffman's excellent website: Troubleshooting Electronics
Solving These Common Problems:
There are a wide variety of problems that can occur in your equipment and I am not a service technician by profession, so my sample is relatively small. Despite the small sample size, I have discovered a few common trends that I think might be helpful for you. What I have indicated here are the problems that I have run across most frequently in the past 15 to 20 years. Let's take them one at a time and in the order I have presented them above. Each solution requires you to disassemble your equipment. In many cases, a minimum of tools are necessary. As the repairs grow in complexity, though, you will likely need to purchase some replacement parts, but this is not as big of a deal as it sounds like.
Solution #1. Channel Imbalances:
Let's start with the basics, we'll build in complexity of exploration and solutions as we progress here. Interesting and frustrating problems happen from time to time. One typical problem is speaker-level imbalances where one speaker sounds louder than the other. Other similarly strange and vexing problems occur seemingly out of nowhere such as problems with one source (your DVD player) but not with another (your CD player). The best way to address this type of problem is by being systematic and logical as possible in your approach. If one speaker isn't working or isn't as loud as the other, try to be as logical as you can in tracking down the problem. Try to isolate and remove as many variables as possible and make things as simple as possible.
For example, if one input or one speaker is not working properly, start by switching inputs. Trade the left and right channel inputs. Does the problem remain? Or does it follow the switch you've made? Either way, you've started narrowing things down already. So, here are a few things to try in isolating an input or speaker level issue:
-Swap the left and right input cables.
-Swap the left and right output cables.
-Swap the left and right speakers.
-Use your MP3 player as an input to the set of input jacks that seem to be causing the problem. Alternatively, plug your DVD player into another input.
-If this is a tube amp, swap the input or the output tubes across channels. Also, make sure the tube pins are clean and the tube sockets grip the pins tightly.
Experiment with only one change at a time. If any change makes a difference, you need to look more closely at what it was that you changed. The clear implication here if the symptom changes is that the problem is external to the device you are exploring. If the problem remains after systematically making changes, then the problem is internal to the device you are exploring and not associated with the inputs or outputs. This suggests we need to look a bit more deeply. Perhaps an input selector switch is tarnished or corroded. Perhaps the volume or balance control is similarly tarnished or corroded. Perhaps there is a loose RCA jack, or one of the solder joints between the RCA connector and the circuit board it connects to is broken. Each of these problems is addressed below.
Whatever the scenario, try to be as systematic and logical as possible. Make only a single change at a time and evaluate the results. Eventually, you will narrow things down until the source of the problem becomes clear. Does the problem exist with all inputs to your gear, or only a single input? You get the idea...
Solution #2a. Scratchy Volume Control, Balance, Tone Control, or Selector Switch:
This is the easiest of all repairs to effect on your own and often involves the least amount of dis-assembly. Have you ever rotated the volume/treble/bass/balance control or some other input selector switch and been greeted by an obnoxious noise from your speakers? This is the result of dirty and oxidized electrical contacts. There are a number of electronic cleaners out there and nearly all of them will achieve the same results. A few are shown below and can be found at your local giant W or favorite online store for about $5. These often come with a little red tube so you can reach tight places with some precision.
You'll need to remove the outer cover from your device and find the back side of these controls on the inner circuit board and give them a spray. Look just inside the front panel, typically toward the bottom of the chassis. You want to identify something that looks like what is pictured below:
The red arrows indicate potentiometers, or adjusters for the circuit (volume, balance, treble, bass). On most stereos, these are cheap and inexpensive parts (often, less than $1 each) that tend to oxidize and get dirty rather quickly and easily. Ever have a "gold" ring or watch that turned your skin green? Well, it's the same type of thing going on here - chemical reactions happen over time with inexpensive parts and the crud that develops just needs to cleaned away. Take your spray cleaner, squirt just a bit into any holes or openings you can find on the body of the adjuster and turn the knob back and forth a few times. Then, let it dry for a few minutes or use your air compressor to get rid of any remaining liquid. Put things back together and you're all done. This is about as easy as it gets!
While you have your spray cleaner in your hand, it is useful to give the RCA jacks and speaker connectors on the back of your amp a squirt as well just to make sure they are clean.
Solution #2b. Intermittent Electrical Connections caused by Dirty/Tarnished/Oxidized wire contacts:
Fixing this type of problem is very similar to what I described above, and is exactly what crippled the Marantz AV8003 pre-amplifier that I use in my basement home theater. Unfortunately, though, you cannot prevent this problem from happening, other than trying to keep excessive humidity or cigar/cigarette smoke out of your home. Every piece of electronics has a swich, or connector, or jumper wires on it somewhere. Your goal is to carefully and sytematically clean each and every one of them. Depending on what type of equipment you are working with, the presence of a switch might be obvious from looking at the outside of the unit (knob, dial, head phone jack, etc) or it might live somewhere inside the unit that is not obvious from the outside (think of a tape deck or similar mostly mechanical device). Either way, they ALL need to be cleaned.
I purchased this piece of equipment on E-Bay at a very significant discount from its original retail price. What the seller did not disclose in his auction is that this unit was refurbished by Marantz (meaning the original purchaser had some trouble with it and it was repaired by the manufacturer during its warranty period) and then resold. The individual that I purchased it from claims to have used it in his personal entertainment system at home, but a quick look at his other items for sale revealed a different story. The volume of home electronics that he was selling indicated to me that he made his money ditching B-stock items (mostly refurbished items that no longer carry a warranty) on E-Bay. Thus, I the likelihood of something being wrong with it was already high, but the price was just to good for me to pass by, so I took a risk and purchased it. When it arrived, one of the surround sound output jacks was not functioning. Bingo! This is why it was for sale on E-Bay.
The AV8003 is a fairly sophisticated device - it is also Marantz's flagship product, so there is quite a bit going on under the hood. The problem I was having was with the signal output jacks that I have circled in yellow above. On the left are two columns of standard RCA (unbalanced) jacks. The XLR (balanced) jacks are on the right. Neither the RCA nor the XLR jack for the surround right channel was working, so I figured the problem was not with the jack itself (this is Solution #2 below), but most likely with the signal that goes to the printed circuit board (PCB) on which the jacks are mounted. If your equipment only has RCA jacks, you might need to try several things before you are able to fix it. My philosophy is to try to eliminate as many obvious causes of problems and focus on what is left.
So began my journey into the AV8003. Removing the chassis screws (usually found on the both sides and perimeter of the rear panel) revealed no fewer than 15 separate circuit boards inside! The circuit board for the output signals is again circled in yellow in the image below. I was hoping the problem was with this board, since it was right on top and easiest to get to, but unfortunately I had to dig deeper into the chassis...all of the way to the bottom! UGH!
Once you've opened the chassis and identified the circuit board that you are looking for, you need to find the wires that carry the music signal to this board. I have identified these for you in the image below, again circled in yellow. The wire harness on the right side of the image carries control signals to the relays on the output board as well as the power supply for the components on the board. While it was not my first target, I cleaned this connector as well. The harness that I was really after is on the left side of the image below. The configuration of the wires (one black, one white - both wrapped in a grey insulator) is a dead give away - these are the wires that provide the audio signal to this board.
This wire harness is a 2-part connector. One part is connected to the wires and the other part is soldered to the circuit board below. The two pieces snap together and have a small locking mechanism to help insure they don't fall apart over time. Using a pair of needle nose pliers, GENTLY grasp to top part of the connector and GENTLY wiggle/pull it free from its mate that is soldered to the PCB. It should snap apart fairly easily, but it will take a little bit of effort. Next, get yourself some Electronic Cleaner from your local RadioShack store. Spay a bit of the cleaner into each end of the wire harness and gently scrub the wire contacts with the brush on the can. Be careful you don't get any in your eyes while do this! Use a pair of goggles or hold your head away to prevent squirting yourself. Then use your air compressor (or a can of compressed air - also available from RadioShack) to blow away all of the remaining liquid on the PCB. It is VERY important that the entire board is DRY before you plug it in and turn things on again. If there is any liquid left on the board when you power things up, you run the risk of shorting things out.
After you've cleaned and dried things off, replace the harness and test the results of your work. If you are lucky, you're done and ready to go. This was not the case for me, though. So, I started tracking down the other end of the wires form this harness and found the problem - this was my problem. If I wiggled my wires with the power turned on, I was able to make/break the audio connection - I had the preamp output test tones through a small amplifier and a speaker. Sure enough, the other end of the wire went to the PCB that was most deeply buried in the preamp chassis. This was going to take some time to get to it...
So here we are, nearly 2 hours later... I recommend doing several things in the process of deconstructing your equipment: 1) get a small cup to store the screws as you remove them. Label each cup with something meaningful like "chassis screws," "rear panel screws," and "PCB screws," or some other meaningful label, and 2) label the wire harnesses that you remove along the way. Each wire harness has a numbered label on the PCB right next to that identifies that particular harness. Use masking tape or wire tags or something similar and be sure everything you remove is labelled so you can put it back together again! So after all of that effort, here we are at the other end of the errant wire harness:
The image above shows the "other end" of my wire harness from the output board (on the left). Each pin for the harness is even neatly numbered and labeled with the signal that it carries! This type of connector, though, is different from the one on the other end - no doubt to prevent the cable from being installed backwards. The problem for me, though, was that I was unable to disconnect this one from the circuit board - I couldn't figure out the locking mechanism for it. This complicated things just a bit...
First, I again used my needle nose pliers and GENTLY tugged on each individual wire to make sure that the wire itself wasn't broken/detached and just laying there looking like everything was fine. Each wire passed this test. Next, out came the can of electronic cleaner again. Since I couldn't get this harness apart, I thoroughly soaked it in cleaner and scrubbed it with the brush. Scrubbing made sure that each wire was wiggled around a bit thus allowing the cleaner to fully penetrate the harness and remove whatever corrosion was on the actual wire contacts. Don't forget to use compressed air to remove the remaining liquid from the board.
Normally, I would have been done here and have started to put everything back together again for a test run to see if my problem was cured. But since it took so long to get down into the chassis (and it would take an equal amount of time to reassemble everything), I was looking to prevent having to do this again so I tried one more thing. I wanted to get to the bottom side of this circuit board to insure that none of the solder joints for the harness were broken. Remembering that this was returned for warranty service, I wanted to be thorough with my repair the first time. So, I also removed this bottom board and subjected it to the treatment below for Solution #2.
Solution #2c. Intermittent Electrical Connections Caused by a Broken Solder Joint:
This particular problem is what caused another output signal from my Marantz AV9000 preamp that I use in my family room to fail. As I illustrated above, you need to identity the outputs that are causing trouble, open the chassis, and disassemble it to the point where you have access to the bottom side of the circuit board that contains the suspected broken solder joint. Hopefully, this circuit board is somewhere near the top of the chassis and you won't need to perform a complete disassembly as I had to above.
Once you have liberated this circuit board from the chassis (though sometimes you don't need to completely remove it - you just need access to the bottom of the board), it's time to have a closer look. You might want to use a magnifying glass and some extra light to see what is going on. The images below show what you are looking for.
The image above shows the bottom of the PCB that contains the RCA outputs for one of my preamps. I have again circled the area of interest. These are the points where the RCA plug actually attaches to the circuit board. If these jacks are not handled with care or they are bumped, forced against the wall, or experience any other form of trauma, they can easily become disconnected from the circuit board. All it takes is a hairline fracture in the solder joint. This fracture may or may not be visible even when using a magnifying glass. Some examples are below. Again, you need to inspect carefully here- use a bright light and a magnifying glass while you gently wiggle things around. If you find any cracks, hairlines, or anything that wiggles when it shouldn't, it is likely you have a broken solder joint.
The easiest thing to do here is simply and carefully re-melt this solder joint and let it cool again. For this, you'll need a low-wattage soldering iron with a small pointed tip as shown below.
Soldering irons come in a variety of temperature ranges. The one you want for working on a PCB is NO MORE THAN 25-30 watts - this will be indicated on the packaging. A soldering iron that is 50w, 70w, or higher, will get TOO HOT and will do more damage than good. Electronic components are heat sensitive and can easily be destroyed by a too-hot iron. You should be able to find a decent soldering iron for less than $10. Once your soldering iron has had a chance to warm up, just carefully touch the tip to silver mound of solder and hold it there for several seconds (4-5 seconds should be sufficient). You want to see the solder completely melt and warm up the metal it touches. Both the metal tab and solder pad on the circuit board need to be heated up. Remove the iron and let the joint cool down again. Do this with each connector that exhibits an intermittent connection and you should be done!
Now just be careful putting everything back together again and you should be up and running!
This very same problem crippled the first computer that I purchased - I was 13 years old and my beloved TRS-80 Color Computer from Radio Shack would sometimes turn on and sometimes not. After lifting the cover and playing around a little bit, I found the problem. The solder joint that connected the power supply transformer to the circuit board had broken. Apparently, the computer was bumped/dropped and the weight of the transformer caused it to break the solder joint. I found it by wiggling the circuit boards with the computer plugged in and turned on. When I got to this board, I saw (and heard!) a VERY tiny spark at the broken joint. A little heat from my soldering iron reflowed the joint and my computer was as good as new!
Solution #2d. Your Monster Cable Ripped the RCA Jack From Your Equipment:
Yep, lots of people love their Monster brand cables because they make a nice, tight connection between your various pieces of equipment, but sometimes that grip is just a little too tight when it comes time to remove the cables. What results is below:
Note the outer collar has been pulled off of your equipment is is laying on the paper below. While this might initially trigger thoughts of panic and anger, it, too, is relatively easy to repair. You first need to open the chassis and remove the PCB to which it used to be attached. A repair of this type is usually as simple and sticking the metal collar back into place (maybe with just the tiniest dab of glue on the inside of the metal collar to help keep it more firmly in place next time...) and reflowing any connection to the circuit board again. In some cases, you won't need to solder anything at all - simply replacing the collar is enough to make things work again. If you are looking for a replacement collar, have a look at Digikey, Mouser, or E-bay for an "RCA input jack" to use as a donor for a new collar. Carefully disassemble the donor part, add a drop or two of super glue or JB Weld, and push things back together again. Then pick a different brand of cables to use...
Solution #3a. Old/Dead Electrolytic Capacitors:
As I indicated above, capacitors are the Achilles' Heel for all modern electroincs. Capacitors are used in ALL devices and ALL capacitors eventually fail (some as soon five years). If your device has recently stopped working and you didn't do something silly to cause this problem, I'll bet my next paycheck that it has bad capacitors inside. The good news is that capacitors are readily available and inexpensive, too! The discussion in this section applies to "modern" black-box type solid state (no vacuum tubes) electronics (CD player, receiver/amplifier, sattelite receiver, television, etc that was manufactured within the past 20-30 year). For a treatment of exploring capacitors in vacuum tube radios and amplifiers, please see this page.
Years after repairing an intermittent output signal from my Marantz AV9000 preamp (caused by a broken solder joint on an RCA output jack), it began to fail again. One day, it just shut down. Nothing. No power, no lights, just dead. OK, this seemed simple enough - my guess was a blown fuse. So I opened the chassis and found the fuse right next to the power supply transformer (generally, the transformer is the largest and heaviest component inside of your equipment). Literally 20 minutes later (open the chassis, replace the fuse, close the chassis, reconnect all of the wires) I was back up and running. No big deal, I figured, as the equipment was 5-7 years old at the time. Well, three weeks later, that fuse blew again. I thought that was strange, but I replaced it again. This time the new fuse lasted only 3 hours. OK, something else was clearly wrong here... Time to dig a little deeper. One thing I have learned over the years is that capacitors fail (often as a short-circuit) and cause all kinds of trouble when they do. The thought of replacing these electronic devices (either individually or together) was enough to induce sticker shock in anyone! The one place in all electronics where the capacitors are most likely to fail is the place where they experience the greatest level of stress in their daily lives: The Power Supply.
Note: before taking your soldering iron and attempting to replace ANYTHING on your circuit board, be sure to have replaced the CAPACITORS FIRST. Far and away, these are the first things to go bad on a circuit board, so logic dictates that we start here. Some people will advocate careful visual inspection and replacing only the capacitors that look like the tops have bulged. A bulged top is a sure sign that a capacitor is bad! However, NONE of the bad caps I have replaced have ever appeared bulged or physically distored in any way! While there is sometimes physical evidence to spot (bulged cap, dried up or corroded fluid that leaked out of the caps onto the PCB - see below) there are ways for caps to fail that don't leave physical evidence behind for you to find with your own eyes. My rule is simple: Never trust an electrolytic capacitor.
Here are a few images of what leaky electrolytic capacitors look like. Sometimes it it obvious (corrosion of the copper pad for C105), other times you need a strong light, a magnifier, and have to tilt the board around until you see it in a reflection (fluid leaked and covering the R83 label on the PCB). These are obvious signs of trouble.
Below is an image of several bulged capacitors.
Here is my simple rule: Is the device that you are working on more than 5-10 years old? If yes, then ALL of the power supply capacitors need to be replaced. You already need to place an order for new parts, so you have already invested time, money, and shipping costs. Adding $10 more to your order for a handful of additional new caps the first time around saves another week of waiting for the mail and additional shipping charges when the first set of caps you replaced don't solve your problem because you left some old ones in there... When dealing with power supplies, REPLACE ALL OF YOUR CAPACITORS. Trying to individually test capacitors to isloate a bad one is a problematic premise from the beginning. You need to have and know how to use a rather expensive test meter. Additionally, you typically need to remove a capacitor from the circuit (or at least lift one leg) in order to isloate it to perform any kind of meaningful test. Does your meter measure capacitance? Most $30 digital multi meters can do this, though this test may or may not reveal a problem to you. Can your DMM also measure a capacitor's Dissipation Factor? This often provides a bit more insight, but requires a more expensive meter, typically over $100 or so. Another useful test is to measure equivelant series resistance (ESR). This, combined with measuring DF will get you closer to identifying a potentially bad cap. On top of that, some caps measure good with your digital meter only to fail when an actual operating voltage is applied, thus the ideal test is to test the capacitor for leakage current. No digital multi meter can test a cap for leakage current - this requires an antique tube-based tester with an analog meter and the application of working voltage to the capacitor. Thus, capacitors are often tricky to properly diagnose, despite their innocent appearance. In the long run, it is less frustrating to carefully replace all of them.
The image above shows six capacitors located between two power regulators/transistors (devices with silver screws through them) that generate enough heat to require rather substantial heat sinks (aluminum blocks that the screws go into) be attached to them. Four of these caps are visibly buldged and are definitely not to be trusted. But given this context, it is safer/more effective/more useful to REPLACE ALL SIX capacitors. Here is the logic: If one cap is old enough / has been exposed to enough excess heat / has been subject to excess voltage / has lost its electrolytic fluid / etc. to the point where it has failed, what makes you think the cap right next to it is still in perfect operating condition? Birds of a feather... ALL OF THESE CAPS MUST GO!
Within three months of repairing my preamp, the same symptoms appeared with our Yamaha Clavinova CVP-85A electric piano and our Mitsubishi rear-projector high definition television. I'm wondering if we experienced a lightning strike nearby that over-juiced all of major electronics... One day it worked, the next day it didn't. This time, the fuses were all intact, though...
In the case of my Mitsubishi rear projector television, the caps on the $1200 (price quote from Mitsubishi) power module board were rated at 16v, but the power supply in this section operated at 25v! Duh! Not sure if this one was an instance of planned service calls as a revenue generating technique on the part of Mitsubishi, or was just the product of a careless/lazy engineer that chose the wrong part for the wrong job. Either way, it was a simple fix that cost me less than $10 in new caps.
Diggin in: The power supply in most equipment is pretty easy to locate, it's the board that connects directly to the transformer that also has the fuses mounted to it.
The image above is the power supply for our Yamaha Clavinova CVP electric piano. The power transformer is the large item on the left side of the image with the brown, yellow, orange, and red wires coming out of it. You can see the orange and red wires that connect the transformer to the power supply circuit board to the right (circled in red). The fuses (horizontal glass tubes) are even right there! It's a no brainer - we've positively identified the power supply for the piano! Finding the power supply circuit board is virtually the same in all home audio equipment - follow the power cord to the transformer, follow the transformer wires to the power supply board, then find the caps. In the image above, there are two circuit boards, one mounted directly above the other. So I removed the top board to gain access to the bottom board. A close physical inspection of the board and the caps did not reveal anything obvious - no leaks, no bulges, nothing but a clean board. Yet, I was convinced this was the problem (because I had just repaired my Mitsubishi television three weeks prior - it also refused to turn on at all because of dead power supply caps). After removing this circuit board from the chassis, I made a few notes while looking at the circuit board. Each component is labelled on the board. All of the labels for the capacitors start with the letter "C" and have a two- or three-digit number after them. I made a list of each capacitor, its number on the board, and its value. There are three important attributes for capacitors: 1) the voltage rating, 2) the capacitance measurement, and 3) the polarity. All three are important.
In the image above, we can observe each of these attributes. Note the markings on this cap: "25v22uF" - this indicates the voltage rating of the cap (25v) and its capacitance measurement (22uF). What they mean is relatively unimportant for repair purposes, you just need to get a new capacitor with the same capacitance rating (22uF) and the same or higher voltage rating (25v or more). These can easily be found online at places like Mouser and Digikey. I tend to prefer Mouser for smaller orders since they don't have a minimum order amount. The final thing to note about each cap before you begin to remove it is its orientation. Electrolytic capacitors like these usually have a specific polarity or orientation on the board. One leg is for positive voltage and the other leg is for negative voltage. The stripe running down the left side of the cap above indicates its negative leg. The marking on the circuit board also indicates the same: see the vertical bar painted on the board to the left of the cap? This marks the negative leg. Also the diagram directly under the cap (between the legs of the cap) is another indicator for its orientation - the curved end is the negative leg and the straight end is the positive leg. Sometimes the board is marked with a small "+" for the positive leg. For each cap on the power supply board, note its number and position on the board, its voltage, its capacitance, and its polarity orientation. Sometimes taking a close-up image with your digital camera can be a real help when taking things apart. Take a wider-scope picture of the entire PCB and all of its connectors, then go close up for the parts you are interested in replacing. Make sure that your images are sharp, well lit, and don't exhibit glare from a reflected flash that obscures important details. A few minutes spent ahead of time taking pictures can prevent a number of headaches down the road if you've missed something in your notes! Then flip the board over, heat one solder joint with your soldering iron and gently pull that leg up a little. Then heat up the other leg and pull that leg up a little. Going back and forth with some heat and a gentle rocking motion should allow you to remove the cap from the board. Work on one leg at a time and it will go smoothly and easily.
After a week or so, my new caps arrived from Mouser. I spent a few minutes re-inserting the caps into the power supply board and I was back in business! This restored to life my AV9000 preamp, my rear-projector television, and my piano! Success - $10k worth of electroincs repaired for just a few dollars and some time!
But three weeks later, the piano died again! Hmmm... I had replaced the caps on the bottom power supply board, but I left the ones on the top circuit board alone. Doh! Here we go again. Extract the board, take a few pictures, make a list of all of the caps and their values, remove the caps, order new ones, wait a week for delivery, install new caps, put it all back together again, and fire it up... Fizzle, sizzle, crackle, pop! Yes, even a little of the magic white smoke escaped from the third circuit board in the piano! YIKES!! Now it was really fried!
Well, there was still some hope. I guess that the power supply on the first board I repaired was faulty and what actually caused the piano to not turn on in the first place. Once that part of the power supply was restored, the next board in the chain failed (I should have seen this one coming). This is most likely because it's the first time in a long time it had received a proper power supply. So I fixed the second component of the power supply. Now the third and final board in the chain had failed (surprise, surprise - they are all the same age... See what I mean about replacing ALL of the caps?). Only the capacitors on this board were a bit different. Instead of being the upright electrolytic "cans" with wire leads that go through the circuit board, they were surface mount capacitors. Hmmm - I had never worked on these before. I didn't take any pictures of this third board (the digital synthesizer) before I began working on it, though. Instead, the image below is just a random pic I grabbed from the web to show the surface mount capacitors (I circled a few of them in yellow).
Below is a closer image of this type of surface mount capacitor.
The three important attributes are easily discernable on this cap as well: its a 47uF, 35v cap and the negative lead is on the left (indicated by the black stripe). The third and final circuit board for the digital piano had no fewer than 107 of these caps on it! Looking closely with a flashlight, I could see what looked like an old, dried up leak on the circuit board under many (but not all) of these caps. This was the final bit of evidence I was looking for - the leaked electrolytic fluid! Yep, these caps needed to be replaced as well. Truth be told, I would have replaced all of these even if I didn't find any evidence of leaks. Removing these was pretty simple. I just heated each side with my soldering iron, alternating sides every few seconds and then lifted it off the board with a pair of needle nose pliers. Since I don't have the tools to re-mount these types of caps (though if you search YouTube, you can find a number of instructional videos that are very good), I decided that I would replace them with the same type of electrolytic caps I used for the power supply. Though, because many of them were packed into a relatively small area, I spent some time looking through the Mouser online catalog for the smallest ones I could find that were the appropriate value.
The image above shows the new cap installed on the circuit board where the old cap once lived. I cut the leads for the new cap to shorten them and bent the bottoms of the leads at right angles to provide "feet" that I could solder to the pads on the PCB (see above). Immediately to the right of the new cap, you can see an unused space on this board where an addiontal cap could be installed (probably for a different version of this particular digital piano). Compare these two spots C101 and C106 in the image. See the dark green splotches surrounding the C101 space on the left and right inside the white box? This is where electrolytic fluid leaked out and began eating away at the PCB. This is another sure sign of leaking caps!
After cutting, bending, and soldering over 100 new caps (this took me about 3 hours), the synthesizer board looked like a downtown high-rise on the board compared to its original appearance:
A few of the capacitor values were not directly available in the larger "through-hole" style caps, though. So I had to add two or sometimes three smaller caps together (just solder them in parallel, positive legs togther and negative legs together) in order to get the value that I needed. When joining caps in parallel, just add their values together: a 47uF cap in parallel with a 100uF cap makes a 147uF cap. This way, you can be a little creative to create a value that is not readily available.
This time, everything worked! Pfew - no damage to the IC chips on the board (smoke these and it's really game over). And this electric piano has been running strong for years since! A little bit of persistence, some desire to explore and learn, and things work just fine! I don't know if you've ever priced a new mid- to high-tiered digital piano (no, not the three-digit-price-tag ones from Sam's Club or Costco...). I did after the third time this one failed and I smoked the caps on the synthesizer board. After I recovered from the sticker shock inducing high-four-digit pricetag - I decided to give it another try and tackle the caps on the synthesizer board. I am very pleased that I did! Persistance and some level of adventurousness pays off. I figured I had nothing to lose since it was already non-functional...
Here are two very nice writeups that provides some additional detials on replacing caps on a circuit board and here.
Solution #3b. FIRE! and Other Serious Trauma:
OK, now the trouble is pretty serious! This will take some work, but if you are lucky, the damage isn't too great and can be repaired with a few new parts. One nice little amp that I have was offered on E-Bay as a non-functioning unit, perhaps one that could be used for parts. It is an A-VR401 by Onkyo and originally sold for $1000. My E-Bay price? Less than $20. I was again willing to gamble a few bucks that I could make it work. When it arrived, I saw that the trouble was pretty severe. Look at the brown charring on the circuit board at the bottom of the image just under the left side of the grey cabling below the two black capactiors:
This is an integrated receiver and amplifier and is FAR more simple in design and construction than my AV80003 preamp. With only one main circuit board to work with, I figured this wouldn't be too bad, despite the damage it had sustained. Here are a few close up shots of the specific trouble:
This picture is from after I repaired the amp. The original resistors obviously overheated, caught fire, and burned a hole in circuit board. Ouch! Talk about trouble, it's a wonder that the seller still had a home in which to live! Damage like this comes from two tyipcal sources. The first is not following the manufacturer's instructions that are provided in every owner's manual: The essential rule is to provide plenty of breathing room for equipment that generates heat - especially power amplifiers! Looking again at the top of the chassis revealed the tell-tale signs: I found a round dust-imprint on the top of each corner of the chassis. Someone had stacked at least one (and likely more...) piece of equipment on top of this amplifier (probably a CD player or other such device). Even worse, it was probably placed inside of a cabinet or entertainment center with a glass door (aka, oxygen deprivation chamber)! Doh! This completely starves heat generating equipment of necessary cool, fresh air. Over time, components begin to break down and then all it takes is a few minutes of high power draw (during a party, perhaps?) and things begin to go terribly wrong as they did here.
Another likely source of overheated resistors or diodes this close to the power supply (those four black diodes with grey stripes are a dead giveaway) are those two big, black capacitors directly to the left (thanks to Ross for pointing this out). As pointed out above, as caps begin to fail, they often form a short circuit. This is typically a gradual process, whereby the resistance offered by the caps increases over time. As the resistance increases, it causes greater and greater stress on the doides and resistors in this part of the circuit. Eventually, these other devices generate excessive heat and fail themselves, though they are in this case the symptom, not the cause of the actual problem. See above about replacing capacitors.
Either way, the previous owner is quite lucky to still have a home!
In this image, we see more brown and burned spots on the circuit board, this time below a transistor. This repair required obtaining a service manual - typically available on E-Bay for about $5. The service manual provided the identity (values and ratings) of the burned resistors as well as the specific types of transistors. For good measure, I replaced every component on the board where there was obvious evidence of extreme heat from that component. All together, I ordered fewer than 10 parts for a total cost of less than $15. So there you have it, less than $35 ($20 for purchase of a dead amp, $15 for parts) for an amp that several years earlier sold for $1000 retail. About a year after getting this unit up and running again, it began blowing the main fuse. The cause? Bad power supply caps! This shouldn't be a surprise at this point...
Granted, I've only presented a handful of fixes. Certainly, there exists a wide array of problems that can arise and this is only a small portion of them. I haven't addressed anything such as failure of digital components for these are much harder to diagnose and even harder to repair on your own. What I have presented are problems that have occurred with equipment that I have owned and their solutions. These are things that people with just a little experience should be able to tackle on their own. Hopefully, my experiences can help provide a bit of confidence for you to tackle your own repairs. There is really not much to risk if the device has already stopped working...
It has been my observation that people are far too quick to part with things when they stop working! I have resurrected over $15k worth of electronics during the past several years. Starting with nothing more than some soldering skills and a desire to avoid a repair/replacement bill, I have been able to fix a great number of devices. ALL of these devices are still running today!
So what are you waiting for? Go get yourself some electronics cleaner, a soldering iron, some solder, and bring those dead audio/video components back to life! Just remember to unplug everything and discharge your power capacitors before you go poking around inside the case!
Follow up: It's always great to hear that I've been able to help!
Thank you for your article on repairing audio components. I was frustrated by intermittent center-channel output on the Sony receiver we use for daytime listening, and your web page encouraged me to resolder the speaker output terminals on the PCB. The joints looked just fine, but resoldering them worked wonders.
A thousand thanks!
Thanks for the quick and informative rundown on DIY electronic repairs. Ive been successful on a few small fixes with my soldering iron, now I'm trying to repair an Onkyo subwoofer that won't power on.
Thanks to your efforts, I now have a quick and easy to understand checklist of things to do once I crack it open.