I have purchased electrolytic capacitors (Nichicon ES bipolar for decoupling in audio paths and FG Fine Gold for anything else) to recap my beloved Harman Kardon A402 from 1976 (capacitors have the date code from the same year). When I desoldered the first one (ELNA) I measured its capacitance... nominal, ESR... lower than the new ones. I tried another and another one and all the same, all of them are absolutely fine.
I tried also PSU caps ELNA 4700/50 and the same, ESR is so small that I can't measure even it, 5 mOhms or so.
So all the fun in the recap is spoiled, guys what is going on? These are 45 years old caps, they should theoretically lose their parameters after these years...
I tried also PSU caps ELNA 4700/50 and the same, ESR is so small that I can't measure even it, 5 mOhms or so.
So all the fun in the recap is spoiled, guys what is going on? These are 45 years old caps, they should theoretically lose their parameters after these years...
Hours service has a lot to do with cap condition.
Caps that have never been heated don't outgas water. Typical complaint on organforum, happy new owner buys a 35 year old organ, plays it a couple of weeks, great joy. Then it quits. Why? Rubber seals of e-caps in storage deteriorate due to oxygen, but it takes a few hours of warmth to evaporate the water past those seals.
I don't re-e-cap until amp shows lower than specified power out the speaker terminals, or it sounds bad. I'm listening now to a 1990? MMA-875t with original caps. Probably <12 hours use 1990-2020 due to a bad solder joint from the factory. Bought unit off ebay, found & repaired bad joint, have used it 6-12 hours a day for a couple of months, no new caps.
Enjoy your antique until the grim reaper takes his harvest. Usually unit sounds "polite" on 50 db range material (classical only) well before caps blow the fuse. Polite means no volume peaks. Worst I've measured, after a 1980 amp went silent in a Sunday service, Monday the S-100 was measuring 2 watts on the 4 ohm speaker. New rail caps took it to 40 w/ch, all new ecaps (some weird size bipolars took weeks to find) took it to 100 w/ch.
Caps that have never been heated don't outgas water. Typical complaint on organforum, happy new owner buys a 35 year old organ, plays it a couple of weeks, great joy. Then it quits. Why? Rubber seals of e-caps in storage deteriorate due to oxygen, but it takes a few hours of warmth to evaporate the water past those seals.
I don't re-e-cap until amp shows lower than specified power out the speaker terminals, or it sounds bad. I'm listening now to a 1990? MMA-875t with original caps. Probably <12 hours use 1990-2020 due to a bad solder joint from the factory. Bought unit off ebay, found & repaired bad joint, have used it 6-12 hours a day for a couple of months, no new caps.
Enjoy your antique until the grim reaper takes his harvest. Usually unit sounds "polite" on 50 db range material (classical only) well before caps blow the fuse. Polite means no volume peaks. Worst I've measured, after a 1980 amp went silent in a Sunday service, Monday the S-100 was measuring 2 watts on the 4 ohm speaker. New rail caps took it to 40 w/ch, all new ecaps (some weird size bipolars took weeks to find) took it to 100 w/ch.
I have restored 50+ years old amplifiers with factory fitted large main filter capacitors with low leakage, low ESR and nominal capacity - like new. It is not unusual. I will still replace them if they have a rubber seal and look discolored or degraded, as moisture could enter the can and generate a failure after a little while as described by indianajo. When the capacitor looks and measure like new and the amplifier is working properly, I avoid replacing it unless a modern replacement fits in exactly the same place without compromising the original look. A new quality capacitor is always better than the old one, although it probably won't last that long. Smaller electrolytic capacitors are degraded or completely dead on amplifiers of this age, so I always replace them whithout checking them or waiting for a total failure.
Thank you guys for your inputs. Taking into account that there is still an original bulb and it is still working might be an indication that the amp wasn't working for a long period of time... or maybe decades ago bulbs were much better than these days 🙂
Maybe I will re-cap this amp anyway.
BTW This amplifier has quite an unusual filtering power capacitors (4700/50) with three legs, one is unused, the pinout is about 13.5mm between + and -.
Maybe I will re-cap this amp anyway.
BTW This amplifier has quite an unusual filtering power capacitors (4700/50) with three legs, one is unused, the pinout is about 13.5mm between + and -.
Perhaps worthwhile doing a leakage current test to see if original and replacement caps meet spec.
> Harman Kardon A402 from 1976 (capacitors have the date code from the same year). ...., all of them are absolutely fine.
Sidney must be turning-over in his grave. Clearly he PAID TOO MUCH back in 1976. I know he got better at sourcing just-good-enough caps later.
Sidney must be turning-over in his grave. Clearly he PAID TOO MUCH back in 1976. I know he got better at sourcing just-good-enough caps later.
I just powered up an old RCA Victor AM/FM table radio from 1952.
Has a 5Y3 rectifier feeding a 30/50/30 can cap.
6V6 output tube, 8 inch speaker.
Guess what, I had to put my ear to the speaker to even hear any faint hum.
Has a 5Y3 rectifier feeding a 30/50/30 can cap.
6V6 output tube, 8 inch speaker.
Guess what, I had to put my ear to the speaker to even hear any faint hum.
if the main filter cap were shorted it would not show the nominal capacity, it would also blow the fuse.
If you're referring to that old RCA radio, it actually played nicely on the bench, both AM and FM bands, asides from some scratchy controls.
It's now shelved, for a rainy day project.