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 The slightly rolled-off and thin bottom end to which I had grown accustomed has been replaced by a warmer and more aggressive punch.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!
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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