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EE Minimax DAC repair

Hello Gang,

Although I don't consider myself a Newbie when it comes to electronics or fiddling with technology (been doing it for over 20 years), I seem to be scratching my head as to what went wrong with my OpAmp swap. As per Doug's article, I tried the OPA2604 (dual) in U1/U2 and AD797B (single) in U6/U7 then fired up my previously working DAC. There was little or distorted output from the unit, which I then shut off, inspected interior connections, and tried again; the unit would not start up. Based on visual inspection, there does not seem to be anything obvious wrong with the unit - the fuse and power line are fine (I tried another just in case) no "leakage" or "carbon trails" on the board or otherwise.

Would anyone have suggestions as how to troubleshoot / fix this or know of a qualified / reputable repair person that can?

Thanks in advance.
daveaudiony

Showing 3 responses by mofimadness

mofimadness's avatar
mofimadness
5,363 posts
 
I have the same exact op-amps in mine. When I first installed them, (before I repowered it up), I noticed I missed the prongs on one side of the op-amp chip. It, at first, looked perfect, but I got a little closer and saw what I did. Make sure you have all the pins pushed in and that none of them have "folded" under the chip itself.

I would pull them all back out and try again. The pins are really small and very easy to bend under or miss the holes completely, like I did.

Also make sure they are oriented the correct way.

For repair Bill at Morning Star Audio, (the importer can help).

bill@morningstaraudio.com
mofimadness's avatar
mofimadness
5,363 posts
 
I'm just getting ready to order the DEXA op amps for mine. I'll report back after I have a good grasp on their sonic signatures.

As I stated above, I have the same op amps you tried and they do indeed sound very good.

Sorry you are still having trouble.
mofimadness's avatar
mofimadness
5,363 posts
 
I just sent Bill a link to this thread. I'm sure he can clear up the confusion.
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