Fully Re-Capped Onkyo M-504

X-One

New Member
Hi all-
I picked up this M504 last spring and have enjoyed it... ambivalently knowing it doesn't NEED caps, but could probably benefit from them. There are a lot of general posts stating that 30+yr old caps are end-of-life, and quite a few threads here and other forums about how the M504 is so difficult to re-cap. It's not. More importantly, it's worth it!

This was not my first re-cap, but it was my second ;) Firstly, the op-amp and all the other small electrolytics are really easy to knock out. The amp disassembles very easily, the ribbon cables release from the ZIFs and the main board never has to be removed. I spent ~$30 for all Elna Silmic IIs, and a few Nichicon FineGolds. The main filter caps were harder to find, and more expensive. I found Panasonic ECE-T2AP103EA for ~$125. These are 100v 10,000uf, 35x80mm (same size as oem).
The challenging part is adapting these 2-pins to the 4-pin format. For this I used a couple feet of 14g romex ground wire, cut, bent into hoops to emulate the paired pins, and soldered to the new cap pins.
I relieved the main cap heatsink holes just a couple mm to clear the wider pin spacing on the caps themselves, but was able to position the copper hoops to use the original board holes.
The new caps are NOT glued down to the heatsink, so until I glue, strap or otherwise fasten the caps together I don't want to move the amp much.
Definitely a hard part was getting enough heat into the copper ground plates to flow the solder, but not setting the whole amp on fire and burning down my condo. My 100w gun didn't even warm it up, and I finally went at it with the propane torch, VERY low flame, working very fast. Get a big, high-wattage iron or crack-pipe torch before you even attempt. PSA: the ground lead wires are glued to the board and if you break that glue you break the ribbon cables and pull up traces. PITA to fix.
I did the LEDs, binding posts, and walnut side panels last summer.
Early listening impressions post-recap? PUNCHIER. The slightly rolled-off and thin bottom end to which I had grown accustomed has been replaced by a warmer and more aggressive punch. Which is nice, as my Vienna Acoustics Bachs aren't exactly earth-movers, and I don't use a pre-amp or eq of any kind. All my digital goes direct from my Cambridge Audio Stream Magic 6 II, which has optional volume control. Analog comes from two vintage and one Pro-Ject TT, through a (fully re-capped) Marantz 2270 pre-out.
Bottom line; I liked this amp before but I love it now. With new caps it's already warmer, punchier and more articulate. Mids and highs are even better than before too, with sweet imaging, roomy staging, and good vocals placement. Time will tell whether this "breaks in" and gets even better.
Anyone planning to do this job, I can put together a BOM and more detailed procedure. Thanks to all the previous posters who're supporting this great '80s hardware!
 

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Very nice work and the amp is gorgeous!
Pat yourself on the back and crack open a cold one, sit back and enjoy your tunes!
 
And at the risk of re-stating the well-established; these amps NEED higher voltage mains. My rails were 73v, so the OEM 80v caps are much too close.
All 8 of the original mains tested well with spec when they came out. I did not test every little cap, but the few I did were also spot-on. So in my experience, fresh caps will improve the sound of the amp even when the old ones are still functional.
 
Just to follow up with a few miles under it's belt;
The punchiness has eased a little (or maybe I just got used to it). But the amp sounds fantastic. It doesn't say Levinson on it, but for $350 off CL, plus $150 in parts, and a couple evenings I'm quite satisfied. Now I'm starting to look critically at my speakers. Having spent a little time listening around it's going to be tough to beat the VAs within my pay grade.
 
LOL he called me an "expert"!
Honestly, thank you. This is how I've always learned:
1. decide to tear apart and mess with something I have no business messing with.
2. start climbing that steep bottom part of the learning curve. Terrified, even self-loathing, but then I start figuring it out.

I did my first engine re-build on a '92 Porsche 911 Turbo. I had NO business tearing it down, but by the shakedown drive I knew exactly what I was doing.
 
I got one I'm getting ready to open up. The display lights were strobing with the music before it died, and now it won't fire up. I see a couple of red LED's lit but that's about all. I may need your BOM.
 
A friend of mine has two and it just kills me to see them sit! (Someday it would be nice to watch those needles moving to independently to push worthy speaks.)

Thanks for proving "meter love" can end up being as good a reason as any to end up with great....and glad good friendships allow for bitching!
 
Awesome thanks for the inspiration.

I just got an M-5060r working after picking it up for peanuts last year. Now that it's working I plan on a full re-cap and new binding posts. Good to see those big 4-pin caps can be replaced with a little ingenuity !
 
Hey @bonzoro I've already had one other request for the BOM. I had some left-overs and a couple addendum orders and I'll need to sit down to assemble a comprehensive (but not superfluous) list. Thanks for all the propps! and @bd1886 nailed the new hashtag #meterlove !!
 
Nice job. Good to hear the old caps still measured good. Makes me not worry so much about recapping mine.
 
hi i also have 2 m-504 Xone if you sill have bom can you send it to me . I know this is a old post any help will do
 
Hey, this is something I've wanted to do to my own wife-gifted wedding present M504.

First, props for tackling this job, and second, think I could get a copy of that??

Hats off, man, she looks sweet, and I'll bet sounds fantastic.

EDIT - Just saw that this thread is a 1 1/2 years old.
 
Great job. Enjoyed the pictures too.
Always looking for one of these at a reasonable price that may need updating.
 
I've done three of these amps.
Finding the main caps is getting difficult.
Fitting the main caps is major surgery.
I posted the how-I-did-it with photos.
It's a piece of work, trust me.
 
And mine is on the bench, staring at me, teasing me... I get nothing on turn on but the power light, no meter lights, no nothing. Every time i grab the meter and try to get into it, i get pulled away.

Feels like the universe is telling me to wait.

Is the BOM of the recap available? maybe if i have the caps handy I'll finally make some progress.
 
One thing with these amps is the confusion with the main power supply capacitors. There are people that will advise going up on the working voltage. But the original caps had been doing fine for all these years?

Lee.
 
One thing with these amps is the confusion with the main power supply capacitors. There are people that will advise going up on the working voltage. But the original caps had been doing fine for all these years?

Lee.

I think the rails are 71V, the original caps are rated 80v. Jumping to 100v makes sense and I think 100v are easier to find IF you can find any for a reasonable price. Needing 8 makes it spendy.
 
And mine is on the bench, staring at me, teasing me... I get nothing on turn on but the power light, no meter lights, no nothing. Every time i grab the meter and try to get into it, i get pulled away.

Feels like the universe is telling me to wait.

Is the BOM of the recap available? maybe if i have the caps handy I'll finally make some progress.

No BOM that I know of.
Not many caps in there.

FWIW, recapping probably won't fix it.

FWIW, they have a voltage divider system that must be balanced and will tear up transistors if it isn't. The odd LED diodes in the front of the amp board are that system. Whatever you do on one side needs to be matched on the other side. I had to replace the original diodes and used actual LEDs to get the voltage drop correct.
 
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