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Why re-cap? Once and For All.

ConradH said:
FWIW, I do a leakage test on every cap I use, to full rated voltage, so they're fully formed.
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Hi Conrad - I'm assuming you're referring to new caps - can I ask if you find many that fail on leakage ? I generally measure them for uF & esr, but I've not considered routinely testing for leakage (I don't work on tube gear).
 
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Actually when I did the PL re-cap, I checked the leakage on the originals I pulled out. I forget the particulars, it was higher than the new ones but still at very acceptable levels. That was the big "beer can" main filters that were actually running a couple volts beyond their rating and had been since 1980. I changed these parts in 2017. The old ones may have checked in electrically OK but I can hear the difference in that amp. I never would have expected any change, I only put the new parts in because I was sick of moving them around. It sounds very improved to me though and I can't explain why that is.
 
Goldie99 said:
Hi Conrad - I'm assuming you're referring to new caps - can I ask if you find many that fail on leakage ? I generally measure them for uF & esr, but I've not considered routinely testing for leakage (I don't work on tube gear).
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Don't think I've ever had a new cap fail any test. I mostly do the leakage and wait for it to drop to be sure the caps are fully formed. I see caps, usually the larger snap-caps, that are near the low end of tolerance. I think they do them that way on purpose to save money. Sometimes if the cap is really close to the lower limit I might toss it and use another, even though it's technically in spec.
 
John Ess said:
The question here is what is a reasonable need for the work to be done? When is enough enough? When does it become a matter of going overboard? I don't think anyone will argue against repair work. Part of the problem involves e cap life. Anyone notice when buying caps what the life in hours is? Usually only a few thousand hours...makes you start thinking that you better turn those puppies on and enjoy them while you can. But an e cap has a few factors to it's life that aren't always easy for us to factor in. How long has the piece of gear sat without being turned on and seriously run? How many old tube amps or radios have you seen that, if started gently with variac and dbt and allowed to sit for some time powered up, would play OK? Maybe not perfectly, but OK. Then you can have somewhat the opposite. Just went through this with my Sony combo player. While looking around inside, I noticed a cap in the switching PS had a very small bulge and the top was covered in reddish brown "goop" that had dried. Not liking the looks of that, I started looking at the service manual, making a list, and placing an order for every e cap on the PS board. The unit was a demo that I had bought, but had let it sit probably 7 years before bringing it back out. Did I go overboard by replacing all of them or was that the sensible thing to do?
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I think possibly that the hour rating is if you run them at the max temperature or at the max voltage or some combination thereof.
 
^Briefly:
"For lifetime estimation at a lower-temperature range, evaluation
test data have not been obtained, and for evaluating long term
endurance, it is necessary to take into account some additional
factors such as deterioration of the rubber seal materials as well
as the diffusion of electrolyte. Accordingly, in Equation (8), Tx
should be 40°C at the lowest for the lifetime calculation purpose,
and also the estimated lifetime (Lx) should be 15 years at the longest".
 
This thread is touching on one about whether there will be techs out there in the future to fix this vintage gear when it becomes antiques. A comment I made in that thread was that there are current techs with strong knowledge of electronics and circuit design. They have gone through the trouble to determine the correct replacement transistors and other actives to use in different pieces when an NLA component dies. With a recap there will be fewer failed caps taking out NLA components (transistors and such) This is another decent reason to recap. As more and more components are no longer being made this will become more important, keep gear operating in its designed safe area of operation to avoid trying to find a piece of unobtanium to fix a unit.
 
Blue Shadow said:
This thread is touching on one about whether there will be techs out there in the future to fix this vintage gear when it becomes antiques. A comment I made in that thread was that there are current techs with strong knowledge of electronics and circuit design. They have gone through the trouble to determine the correct replacement transistors and other actives to use in different pieces when an NLA component dies. With a recap there will be fewer failed caps taking out NLA components (transistors and such) This is another decent reason to recap. As more and more components are no longer being made this will become more important, keep gear operating in its designed safe area of operation to avoid trying to find a piece of unobtanium to fix a unit.
Click to expand...

I agree with this especially as the replacements for NLA parts are also going NLA (see the SanKen MT-200 thread). It sucks but there might be a time when a once cheap and easily replaced part causes a unit to become a doorstop because there just aren't any suitable replacements.
As far as caps, I do my own work and replace them all when I do a restore. I would never just replace caps and leave everything else be. Caps come along with a thorough cleaning, heat sink paste, trimmer pots, switch cleaning, solder joint inspection and retouching, trouble maker caps replacement, etc.
 
For the longest time I considered semiconductors to have infinite life if properly applied. That's close to true for hermetically sealed metal packages, but not really for plastic packages. As equipment ages I think we'll see more and more small signal devices going out of spec or failing entirely.
 
Thanks for the clarification on Leakage / Reforming Conrad - just wanted to check I wasn't missing something.

On the plastic semiconductor encapsulation packages, I'm sure you're correct - plastics age, and will ultimately fail. How long it takes will be highly variable, due to differing plastics compositions & processing conditions, different environmental conditions (think heat, humidity, potentially ozone, UV exposure, etc.), as well as multiple other factors, and possibly not least manufacturer designed in 'obsolescence', that I suspect will become increasingly significant, especially if it's at all cheaper !
 
Hello, I just wanted to get 'in the system' to aid in other noobs/Toshiba owners, I have just completed a near full re-cap of Toshiba SA-735...and the results have been remarkable. It sounded tinny/hollow with no bass and now is sounding like it should. It has had nothing done to it previously as near as I can tell. I have read as much info as I could before attempting to do this. For 20-30 bucks in materials, its a no brainer on an old receiver. I am now going to 're-cap' my other older receiver which is sounding very good and has no issues to my ear...

FYI disclaimer: I am a noob to the audiofile arts, I used a cheap solder iron, a 6 dollar DMM, and a magnifying glass. It took longer to read/write down what I needed to order, than to install them (it seems like anyway). Youtube has helped with the technical know-hows. I tested/compared DC voltages at the transistors before beginning to make sure it was going to be worth it, ie. no other bad problems, deoxited the controls, etc. Some of the capacitors looked fine topside, but bad underneath..leaks, some bulging. It was worth it for this machine, not that bad if your have some skill, and can learn from the resources like this site and youtube.
 
True, the caps I normally replace are in the power amplifier and power supply protection. I think over the years I have needed to replace less then four filter caps because they were bad. So as a rule leave them alone.


Barney
 
Just found this thread. blhagstrom, I am curious, how did those awful looking caps in the original post test out? They don't look like they could possibly be in spec anymore. Maybe they looked so bad you didn't bother putting a meter on them.

Not that I'm questioning whether they needed replacement. :yikes:
 
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