E-mu 1212m modding woes

[slowpogo]

I recently bought a 1212m. It sounded good out of the box, but I read that a few mods can really make it sound great--mainly, replacing the 47uf output caps with something like Black Gates.

I also decided to replace the caps on the digital board, and several others in the analog out section, with Panasonic FCs or FMs, for lower ESR.

So I did the digital board first...I believe there were 5 electrolytics, all of which I replaced. Afterwards I put it back in the PC, and it worked and sounded fine.

So far, so good. On to the analog board. I started with replacing the three 100uf caps in the analog section, then checked the card again. Worked fine. This whole time, I've been quite careful, trying not to leave the iron on anything more than 4-5 seconds, and waiting 20-30 seconds or so between things. It's only a 15W iron, too.

Things seemed to be going great, so I went ahead and replaced about 7 more caps--basically everything on the analog side except the 4 47uf output caps, which have yet to arrive.

I felt I was done for the time being, so I put it back in the PC and fired it up. Uh oh. Card no worky! I hear what seems to be an echo of the hard drive activity through the phones, and if I turn the volume up much, I get loud clicks in succession.

I honestly don't see how I could have damaged anything, I was very careful. The soldering looks good, I cleaned away any flux residue. What is there to do in my situation? How can I diagnose the problem? Is there any solution, or is the card just fried? Any help would be hugely appreciated, I'm feeling somewhat heartbroken right now...

 

[TzeYang]

take pics.

what capacitance values did you swap the caps with?

 

[slowpogo]

I'll try to take pics when I get home.

I used the stock values for everything. Some caps had a higher voltage rating than the stock ones, but capacitance was the same everywhere.

 

[slowpogo]

Unfortunately, I cannot for the life of me figure out how to take a close-up pic of the card with my camera. I just don't know how to use it well enough; it's always blurry, or too bright, etc.

I measured DC offset from the outputs of the analog card, and it's at about 11 volts(!).

I was mistaken about all the solder joints being fine. In a few places, part of the solder pad/ring was ripped out. But there is still metal there, the solder is finding something to bond to, anyway--just not the full pad.

I know several head-fiers have modded the 1212m, and I even recall someone saying he fried his. If you're reading this, any advice would be awesome. If I can't figure it out soon--this place is really my only resource--I'll probably just spend $140 on another one. Thanks again...

 

[TzeYang]

there should be no DC at the output because the huge output caps is there to prevent any AC signals.

Do check your output caps.

 

[slowpogo]

If you mean the four 47uf caps by the DAC, I have not touched them yet, at all. I changed the other caps but left those stock, while I wait for the replacements to arrive.

I did melt some of the casing on one of them, but otherwise they are exactly as they came stock.

 

[TzeYang]

hmmm It's hard to think without a proper schematic. Are the caps BEFORE or AFTER the output stage? (OPAMP stage)

 

[slowpogo]

They are between the DAC and the opamps. I've read that they are actually redundant and can be shorted.

I just checked the DC again and this time it was 600mv for some reason. I realized the clicking it makes when volume is turned is similar to the "power on" clicks my Sound Blaster would make, when I turned on the PC.

 

[Iron_Dreamer]

The caps that you haven't replaced are the "output" or AC-coupling capacitors. I've yet to see a properly functioning 1212M that needed them to have an adequately low DC offset, so generally they are best to be bypassed.

In your case, I'm not sure what went wrong. I never had a 1212M act up due to changing capacitors. I've had problems somewhat similar to what you describe, but when working on th opamps, I'd check them as carefully as possible to ensure there is no solder bridge or other damage. Wish I could be of more help.