Six Common Mistakes Made When Recapping Vintage Electronics

Short little video on common mistakes seen when recapping (replacing capacitors) vintage electronics. This would include vintage stereos, radios, equipment, CBs, ham radio receivers & transmitters, calculators, computers, you name it.
Hopefully this will provide you some tips and hints to use when you go to recap your piece of vintage gear.
Topics include:
- Mistaking Factory Glue for Leaking Capacitors
- Factory Boards and Manuals Marked Wrong
- Capacitors Installed Incorrectly
- Using Larger Capacitors Than Specified
- Buying Electrolytic Capacitors off Ebay
- Replacing Everything at Once

[Graham_Wideman]

And the number 1 mistake... failing to pull out your cell phone and take a few pictures before you start pulling out capacitors.

[fins]

As a retired electronics tech I can say that this is good advice.
I've subscribed because your video is clear & succinct and not padded out to 30 mins like many others do.

[anmeirdi]

Two important issues when recapping with a higher value; 1. never do this with starting capacitors in motors, they need the exact right value. 2. Recapping with a much larger value in a power supply can cause damage to the bridge rectifier, because the current peak when staring up, is much higher then.
An other important issue is the temperature which is mentioned on the capacitor. The switching power supplies before the 1990's often used capacitors, marked with 85°C. This was also one of the reasons of the caused problems. Always use 105°C capacitors for switching power supplies!

[xxmrrickxx]

Nice video. Seeing gear with surface mount PCBs considered “vintage” makes me feel old.

[Strike_Raid]

If you're recaping really old stuff (20's and 30's era), capacitors had a lot of internal conductance that was accounted for in the original circuit that new capacitors don't have. You may need to add a resistor in parallel to keep the circuit 'in tune', and guessing the size of that resistor is really just a guess.

[mudspringer]

"Trust what's on the board not what's in the manual..." Ha yes! I write code for a living. One of the first things they taught us was it maters what the computer does - not what the manual says. Great video thanks for posting it!!

[leroyusa]

What's nice about troubleshooting stereo equipment is that the channel that is in good working order can be a good reference for measurement comparisons. Hard to find problematic components can be detected this way. Just make sure that your reference input signals are exactly the same for the left and right channels. An oscilloscope can also be an excellent visual aid to compare for abnormalities in the defective channel.

[wmw]

Not "Good Stuff". This is "GREAT STUFF". Informative, concise and pragmatic. Bravo Sir!

[jpreza]

Great advice!! I'm guilty of the shotgun approach because I wanted to listen to my vintage receiver right away. More than once, I spent more time trying to figure out where I went wrong with my DMM, hooking up my DBT, reading voltage/current values through everything and trying to read the blurry values from a scanned service manual, playing the AM/FM tuner, hooking up a turntable and using the phono/EQ board, etc. etc. You get the idea.

Take your time. Do one section at a time, and then test your receiver. Another piece of advice is pay attention to the orientation of new transistors vs. old ones. Some older transistors tend to have EBC instead of a more modern ECB.

[em_tion]

"Smooth, rounded, flow. Smooth, rounded, flow. Smooth, flowing, stuff." I meditated and achieved internal peace there, what a voice! :D

[davidlong]

One thing I would add, having worked on computer monitors in the past ( 25 years ago) some brands had that hold down glue that would over time become unstable from heat and age and become conductive on the board. We had to scrape it all off and clean the board really well.

[randycarter]

That glue when it turns brown, instead of yellow, is actually CONDUCTIVE. Especially if it is near something that is starting to corrode. I've fixed many malfunctioning electronics just by chipping that glue off. When it turns brown it becomes brittle facilitating this.

[johnrobinson]

Great video and full of info. Had VCR many years ago with Alzheimer's. Sometimes responded to controls sometimes not. After hours of troubleshooting and consultation with others in the biz, turned out it was an adhesive foam pad (several) on bottom of circuit board between it and metal bottom of machine. After removing pads found affected traces in different states of degradation . The adhesive had eaten into traces and was semi-conducting between them, thus the Alzheimer's symptoms. No clue until pads actually removed to see damage. Rock solid after repair. Do not underestimate any "material" on a board to cause trouble.

[alexispieltin]

This video is excellent, your methodology is all common sense for anyone experienced in servicing electronics. However, when it comes to factory glue, even if you can still identify it correctly, you must remain cautious and always observe precautionary. Some of these glues have proven corrosive or decompose in corrosive material, so if you notice oxidized copper tracks, rotten component legs, you'll probably have to remove that goo, restore PCB and probably change all components touched, resistors and semiconductors. Leaky caps can also smell badly: most of leaky SMD electrolytic capacitors include a fish oil impregnating everything.
And here is also an important point, most quality electrolytics can still work fine after years if used and stored in proper condition. You also need specific equipment to check and test if they really need some replacement: you should measure values and ESR, and for specific uses like high voltage ones, a specific leakage test has to be performed. Of course, with experience or proper documentation, you have a number of specific condensers you will systematically change in 100% of equipment, mostly because their replacement is critical and always cheaper than the component they protect, like high voltage decoupling caps in tube electronics.
And when it comes to components locations or sense, wiring and so, it's also interesting to take a number or pictures and notes along markings.
Rule number one is to take the necessary time to observe and analyse any further action.

[mrnapolean]

I order my caps from Mouser because 1. they typically have good prices, 2. they usually have what im looking for and in stock and 3. I order over the phone to do Will-Call because I live about 20 minutes from the warehouse and I can typically have my Caps the same day or next day and avoid the shipping charge altogether.

From someone who has rebuilt vintage electronics this video is EXCELLENT. Every new electronics tech should see this video.

[ltgood]

I just learnt so much from this short clip. I just dismantled a 1970s JVC amp to repair. I’m so glad I haven’t started on removing parts.

[Zonfeair]

I particularly liked the point that there are factory mistakes as I have found several over the years but did not know about mistakes in service manuals nor was I aware of silk screen mistakes on circuit boards. Thanks for the info.

[stevewilson]

This is great advice. I definitely see these same issues when recapping. Thanks for putting this out there!

[cosmicray]

Thank you for putting the time into this video and helping keep us all safe.