I'm sure this has been asked and answered a million times. Its such a broad question that google searches provide either little or repetitive info. I am a beginner with electronics (probably considered intermediate compared to average population). I know the basics, can follow simple schematics, light arduino programming, etc. I have taken up an interest in vintage electronics and while most of the stuff I buy has easily detectable problems, I have been working on 80's era Akai linear turntable. I've seen a few posts about this turntable elsewhere and the overwhelming responses seem to be that this is an overly complicated nightmare that isn't worth troubleshooting. Looking at the service manual and numerous circuit boards confirm that the amount of engineering and circuitry that went into building something to play a record is overkill. This is probably the worst or best thing to learn on, but I digress.
I've tested the voltages at various parts of this thing, and so far, everything seems to be in spec. Beyond on the electrolytic capacitors (which the esr all seem to be within in normal limits), what are some good components to check? There are a good number of ceramic & film capacitators, lots of resistors and quite a few transistors, not to mention logic gates and other ICs. I suspect the problem lies with the old Fujitsu Microcontroller but I'd like to rule out anything else obvious. Long question short, beyond electrolytic capacitors, what are some other components that can commonly fail? As I go through this I'd like to initially skip over the stuff that is the more reliable. Thank you.
Hi,
I've seen electrolytics fail badly in power supplies in several different power supplies. The ones that do the filtering. They not only develop high ESR but also the capacitance gets very low. I have scope pics somewhere that clearly show this to be the case when they were removed from the device and tested. Replacing them with good quality caps always fixed the power supply.
Transistors in high voltage circuits, like CRT television HV circuit.
Had one rectifier diode fail in the full wave bridge rectifier circuit of a TV once too, only time i ever saw a diode fail in that kind of circuit. I think that may be because they used to think you could get by with a 200v diode in a 120vac bridge rectifier circuit, but not sure about that. Not sure if they improved on that yet either with newer designs.
Here's one from a longer time ago: The non volatile memory could go bad meaning some bits will flip, and since the programming depends on the memory (typical microcontroller chip or other) even one bit flip could crash the system every time it start up, and memory longer ago was not as good as it is too they had less retention time back then. Luckily flash memory and the like improved a lot over the years. However, the guarantee may be 10 years (check that) so 20 years down the road there could still be a failure and again one bit flip could cause the entire system to stop working or start working in a very non typical way with certain features not functional anymore, and unfortunately the only way to fix it is to get a new chip with the memory programmed as it was needed in the old chip.
I had a high quality CRT monitor fail dead one time but never looked into what caused it. I suspect the high voltage circuit transistor. That was surprising because it was a good make and model but it only lasted a little over a year. The monitors of today are made entirely different without a CRT so we probably get much better reliability.
In some cases you just never know what can go bad. The rule of thumb is that the more external connections there are the lower the reliability, and that means external to the components like IC chips and the like. That's why IC chips that do more inside the chip are considered more reliable in general, because most of the connections are inside the chip not outside.
For a bit of a laugh, i've seen very large electrolytics blow up like a cannon fire. The tops would blow right up and out of the body, and would bend the 1/4 inch heavy copper buss bars connecting them into a bank of several capacitors. Quite a site to see and what more what a SOUND to hear when they blow, sounds like a cannon too.
That is regular failure mode for caps that have to put up with ripple current that is too high for them, but it's mainly due to bad design. The incident quoted above was not like that though it was because a technician had a three phase heavy duty variac set to the MAXIMUM voltage when he turned it on, and so the caps blew out immediately. This variac was something like 3 feet high and 1.5 feet diameter, and the shaft was motor driven, so it could put out 10's of kilowatts probably at 300 volts line to neutral with 3 phases.
It's kind of funny because he thought he had the variac turned all the way DOWN to 0v, but he turned it the wrong way up to the MAXIMUM voltage and that was too high for the rectifier capacitors to take.