M4: To recap or not, that is the question!

mtflycaster

Member
Friends -
Long time member, lurker and occasional poster here. I just picked up a near mint M4 that was "not working". Hooked up some cheap speakers and, sure enough, no sound out of one channel, and weak out of the other. Sooo....

I checked rail voltage - fine. Checked DC offset - fine. Checked bias - fine. Maybe an input issue? Cleaned the pots in the rear and voila!! Beautiful sound out of both channels using a Marantz 1090 as a preamp. :banana:

This amp is unmolested. It sounds great with my Polk 10B's, but I know it's electrolytics are old. Should I just use it, or pre-emptively recap it now? And, in looking at the cap list, I see a few .68 and 1.0 uF electrolytics. Can I replace these with film caps, or is that ill-advised?

Thanks, and best to all...

-MTFly
 
I have an M-2 that is 100% original. I also have two P2201 amps (1976) that are 100% original. They continue to work great even when pushed hard on a regular basis.

I won't deny though, if I had money to burn, I would probably get them recapped just for peace of mind.
 
Friends -
Long time member, lurker and occasional poster here. I just picked up a near mint M4 that was "not working". Hooked up some cheap speakers and, sure enough, no sound out of one channel, and weak out of the other. Sooo....

I checked rail voltage - fine. Checked DC offset - fine. Checked bias - fine. Maybe an input issue? Cleaned the pots in the rear and voila!! Beautiful sound out of both channels using a Marantz 1090 as a preamp. :banana:

This amp is unmolested. It sounds great with my Polk 10B's, but I know it's electrolytics are old. Should I just use it, or pre-emptively recap it now? And, in looking at the cap list, I see a few .68 and 1.0 uF electrolytics. Can I replace these with film caps, or is that ill-advised?

Thanks, and best to all...

-MTFly

I would recap it. Yes on the films.
 
I'd bet if you checked the caps the majority of them would be within spec but there would be a few that are out. Problem is you don't know which ones are bad and what problems they are causing. Could be reduced sound quality or could be getting ready to smoke your outputs.

Just for piece of mind and to know that your amp is as good as new I would recap (and replace whatever other components are recommended by those two fellows above me).
 
Thanks very much, gentlemen! Ordered my caps tonight from Digikey. The comment about "getting ready to smoke your outputs" got me motivated...:scratch2:

Ended up ordering the 27,000uF CDE 382LX for the large filter caps...looks like a straightforward swap.

Any other mods or upgrades I should do while I'm in there?

Thanks again!
 
I have an M-2 that is 100% original. I also have two P2201 amps (1976) that are 100% original. They continue to work great even when pushed hard on a regular basis.

I won't deny though, if I had money to burn, I would probably get them recapped just for peace of mind.

I have several pieces here with original caps, including the CR-3020. They're all on the list to be redone at some point but time is money for me and I can hardly find the time anymore to fix the broken sh*t, let alone recap stuff.

:tears:
 
I would do a recap. (there, I said it) That unit is now hitting the age where regardless of 'gut feelings' on originality etc, the films are possibly getting flaky and if you're in there, you might as well do the electros.
 
Finished the recap with no issues, and the amp sounds absolutely awesome! Just need to replace a couple of the pushbutton lamps..maybe LEDs. This is a keeper.
:thmbsp:
 
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