Recapping Vintage Electronics?

[watchnerd]

How necessary or beneficial is it to pre-emptively recap vintage electronics?

I understand the need to replace old failing or leaking capacitors.

But when I read about restorations of vintage electronics, they often to a 'full recap', replacing every original capacitor, regardless of whether the caps have problems or not.

Obviously, this can involve dozens, or even hundreds of new caps, with many hours of desoldering / soldering.

Is this really beneficial or necessary?

 

[amirm]

The issue is that when the caps go, they can take other parts with them. This is why people just replace them all as a form of insurance.

Since I can repair things, I tend to live with them unless I see obvious signs of age such as bulging, leaking, etc.

 

[watchnerd]

The issue is that when the caps go, they can take other parts with them. This is why people just replace them all as a form of insurance.

Since I can repair things, I tend to live with them unless I see obvious signs of age such as bulging, leaking, etc.

Thanks.

Is it true certain kind of caps are more prone to turn into weapons of mass destruction on death than others?

 

[amirm]

Electrolytic caps go bad the most so they are the usual culprit.

 

[watchnerd]

Electrolytic caps go bad the most so they are the usual culprit.

Sorry, I meant brands.

I've heard people blame Frako and other brands as going bad early.

 

[Wombat]

If you are going to replace lots of caps then make sure that you are competent in soldering or you will end up with many bad joints and possibly some overheated components. This is not for the occasional tinkerer. Repairing lifted PCB tracks is a PITA.

 

[WoodyLuvr]

There have always been two schools of thought on this...

The first school will say to replace everything since you have it opened and already working on the board... sometimes just the simple handling of the board outside the case and the introduction of heat on the board may actually speed along some other failures that need to be addressed.

While the second school of thought will say replace only what is absolutely required and leave the rest completely untouched so as to avoid stirring pesky ole' gremlins and/or initiating the mysterious domino effect of failures that is often associated with messing with vintage electronics. They tend to even warn to not even gaze upon the rest of the board for any length of time in fear of inadvertently hexing it!

 

[watchnerd]

If you are going to replace lots of caps then make sure that you are competent in soldering or you will end up with many bad joints and possibly some overheated components. This is not for the occasional tinkerer. Repairing lifted PCB tracks is a PITA.

I'm (or was) a solid amateur.....but waaaay out of practice.

Back in college (20 years ago), i probably touched a soldering iron several times a month for 30 min at a time. But it's probably been 2 years since I last soldered at all.

I actually just ordered one of these silly 'practice soldering' projects:

The only saving grace is that the board I'm thinking of is vintage 1986 or so...no SMCs.

Still, yeah....might be better to pay to have it done.

 

[sergeauckland]

Electrolytic capacitors have a rated life, typically 8000 hours which is only about 1 year, based on being on 24/7. However, that's at rated voltage and rated temperature, typically 85 or 105 degrees. Electrolytics are generally reckoned to double their life for every 10 degrees lower temperature, so if one has an 85 degree rated cap running at an internal temperature of, say 40 degrees, (25 degrees ambient plus some internal heating due to ripple current), then that 8000 hours becomes 128000 hours. At, say, 2 hours a day, that's well over 100 years!

In practice, it's the main reservoirs that get the ripple current and hence the internal heating, so they're the ones that go first, and again, the rating is an average, so there will be some earlier failures, but nevertheless, if the equipment isn't abused and overheated, and the caps are properly rated and not subject to over voltage, then they will last a very long time. I have 40-50 year old equipment still working fine on the original caps.

I only replace electrolytics that show signs of bulging or leaking, if the equipment works to spec, I leave well alone.

S

 

[mansr]

The only saving grace is that the board I'm thinking of is vintage 1986 or so...no SMCs.

What is it?

If you find any caps like these, replace them. Despite not showing any external signs of failure, every single one I've encountered has been bad.

 

[WoodyLuvr]

What is it?

If you find any caps like these, replace them. Despite not showing any external signs of failure, every single one I've encountered has been bad.

View attachment 17897

Definitely them be rotten lil'gremlins!

 

[AnalogSteph]

The first school will say to replace everything since you have it opened and already working on the board... sometimes just the simple handling of the board outside the case and the introduction of heat on the board may actually speed along some other failures that need to be addressed.

While the second school of thought will say replace only what is absolutely required and leave the rest completely untouched so as to avoid stirring pesky ole' gremlins and/or initiating the mysterious domino effect of failures that is often associated with messing with vintage electronics.

And of course, both are right to some degree. Doing a bulk recap on a super fragile board that'll lift pads left and right can be downright suicidal. On the other hand, working in spots that are super hard to access, you'll probably rather want to be safe than sorry. How preficient you are in soldering will be a factor, too.

Then there's the third school equipped with an ESR meter and/or LCR meter. ESR testing can be done in circuit easily, checking for leakage often can't (unless a cap has entirely shorted out, which is rare enough though it has happened). Note: A capacitance reading above spec can be a sign of high leakage.

The problem is, in old age the health of electrolytic capacitors becomes more and more a matter of statistics. How a part has been manufactured (chemistry, seals etc.), how it's being used in circuit, how the device has been used and stored over its lifetime and sheer pot luck can make a huge difference after a few decades. The main filter caps in heavily stressed PA amplifiers can be pretty beat-up after 1-2 decades, while those in home audio equipment often hold up just fine (unless it's a vintage Rotel, where voltage rating has turned out to be a little too tight) and those in the preamp power supply tend to go first. There have been cases when every single sample of one particular value was found to be bad, while others from the same manufacturer tested fine. Conventional electrolytics that have never seen more than a few mV over two or more decades are almost always badly leaky (special low-leakage series parts like the orange Elnas tend to be fine). The blue Philips caps seem to be universally leaky in old age, no matter whether they've been used or not. Apparently those made by (Czechoslovakian) Tesla back in the day were extremely bad, rarely holding up more than a decade.

If in doubt, I would examine the state of the device (if anything is known about its history, all the better), research how other similar devices and the capacitor series used have held up, do some checks on ESR and maybe some spot checks on leakage and capacitance.

 

[watchnerd]

What is it?

The "it" would be the various boards inside a vintage 1986 Revox PR99 Mark 2 reel to reel deck.

 

[Sal1950]

If you are going to replace lots of caps then make sure that you are competent in soldering or you will end up with many bad joints and possibly some overheated components. This is not for the occasional tinkerer. Repairing lifted PCB tracks is a PITA.

Things were so much easier in the days of point to point wiring.

 

[WoodyLuvr]

Things were so much easier in the days of point to point wiring.

But damn it could be noisy... EMI concerns were rampant... and self-oscillation oh my! With all that said I am still a sucker for PTP!

 

[watchnerd]

In my case, the boards in question are things that look like this:

 

[amirm]

In my case, the boards in question are things that look like this:

Given those axial caps, if the pads are not sound and easily lifted with desoldering, then you can just cut the leads half way from above and solder the new parts to them (hold them with a needle nose plier so it won't get too hot and desolder itself). It won't be pretty but will be quite functional and a lot easier than taking them out.

Be sure to note the polarity of course before you cut them out.

 

[mansr]

Given those axial caps, if the pads are not sound and easily lifted with desoldering, then you can just cut the leads half way from above and solder the new parts to them (hold them with a needle nose plier so it won't get too hot and desolder itself). It won't be pretty but will be quite functional and a lot easier than taking them out.

If the leads are cut, the pieces are usually not too hard to remove by pulling them through towards the solder side.

 

[mansr]

In my case, the boards in question are things that look like this:

Those axial caps are almost certainly bad. The radial ones might be OK. They seem to be more durable. I'd probably replace them anyway, just to be sure, especially any that might get warm during operation (mounted near high-power parts or their heat sinks).

 

[watchnerd]

Those axial caps are almost certainly bad. The radial ones might be OK. They seem to be more durable. I'd probably replace them anyway, just to be sure, especially any that might get warm during operation (mounted near high-power parts or their heat sinks).

Given those axial caps, if the pads are not sound and easily lifted with desoldering, then you can just cut the leads half way from above and solder the new parts to them (hold them with a needle nose plier so it won't get too hot and desolder itself). It won't be pretty but will be quite functional and a lot easier than taking them out.

Be sure to note the polarity of course before you cut them out.

Do you guys think the transistors are safe to leave alone?

Some of the recapping 'kits' can be ordered with or without transistors.