M-80 Power Supply Filter Capacitors

bmanone

Active Member
It’s been about 8 months since I repaired and replaced all the electrolytic capacitors in my Yamaha M-80 Stereo Power Amplifier except the large power supply capacitors (2 each 47000uF/45V and 2 each 33000uF/56V). The four capacitors had no sign of failure (no electrical short, no leaking of electrolyte and no bulges), I did not have an LCR meter to test the capacitance or ESR. What will happen if these nearly 30 year old capacitors start to fail: will the amplifiers output start to hum at 60 or 120 Hz; will the output start to clip and cause increased distortion; or will a capacitor failure cause cascade failure of downstream components of the amplifier? These 4 large capacitors are expensive and it’s hard to find any that will fit, so I’ve postponed replacement. If failure of these capacitors is going result no damage to the amplifier, then I’ll wait to replace, but if failure could cause damage then it’s probably time to replace them. Have any of the forum members replaced these 4 large filter capacitors in their M-80 or M-85 (probably the same capacitors, at least they are mounted the same), what did you use for replacements, do you have any photos of the replacement?
Thanks,
Barry
 
As long as the capacitor doesn't short it won't harm anything else. It will however result in hum, distortion, generally bad sound, no sound at all etc. (depends on where it's used in the circuit).
 
As long as the capacitor doesn't short it won't harm anything else. .....

second that.

I had the same dilemma with my MX-1000. Being expensive to replace is only a small part of the problem. Finding these caps in the original physical size is close to impossible.

What I did, is I bought another defunct amp for parts. The caps on the spare amp are good so this is how I stopped worrying :banana:
 
yamaha M-80

It’s been about 8 months since I repaired and replaced all the electrolytic capacitors in my Yamaha M-80 Stereo Power Amplifier except the large power supply capacitors (2 each 47000uF/45V and 2 each 33000uF/56V). The four capacitors had no sign of failure (no electrical short, no leaking of electrolyte and no bulges), I did not have an LCR meter to test the capacitance or ESR. What will happen if these nearly 30 year old capacitors start to fail: will the amplifiers output start to hum at 60 or 120 Hz; will the output start to clip and cause increased distortion; or will a capacitor failure cause cascade failure of downstream components of the amplifier? These 4 large capacitors are expensive and it’s hard to find any that will fit, so I’ve postponed replacement. If failure of these capacitors is going result no damage to the amplifier, then I’ll wait to replace, but if failure could cause damage then it’s probably time to replace them. Have any of the forum members replaced these 4 large filter capacitors in their M-80 or M-85 (probably the same capacitors, at least they are mounted the same), what did you use for replacements, do you have any photos of the replacement?
Thanks,
Barry

All of the above.

Paul
 

I saw that but I still thought that it was worth bringing this up in order to show the extent to which some of the M owners are going to go to in order to accommodate for the unobtainium physical size capacitors, Yamaha used.
I totally agree that mode is extreme and a bad idea. My solution was to get a donor amp, but that is also a half measure since the donor caps are also old.

Another scenario I was thinking about, was to physically alter the main board, essentially to cut it and wire the terminals of the caps. Still, I hope I never have to go that far...
 
I saw that but I still thought that it was worth bringing this up in order to show the extent to which some of the M owners are going to go to in order to accommodate for the unobtainium physical size capacitors, Yamaha used.
I totally agree that mode is extreme and a bad idea. My solution was to get a donor amp, but that is also a half measure since the donor caps are also old.

Another scenario I was thinking about, was to physically alter the main board, essentially to cut it and wire the terminals of the caps. Still, I hope I never have to go that far...

I'm work'n on a alternate solution. Not ready to elaborate at this point.
 
daughter board with a few 10,000uf caps would also work and would still fit in the case.

10,000uf caps can also be easy checked with an ESR meter.
 
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Would Nichicon LQ (M) series caps be sufficiently good for the job?
A US seller on that auction site sells multiples of 3 x 10000uf @80v for fairly low price. I would need about 18 of them for my amp and could nicely mount them on a separate board and still be able to fit them in the case. At this time I am just worry about fakes and if this series is sufficiently good to do the job. Does anyone have any suggestions?
 
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LQ (M) appear discontinued and that may explain the low price. Old new stock....caps deteriorate over time if not used, right?
 
I'd be a go for a group buy if we could find some that would fit without too much customization.
 
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