EE Minimax DAC repair

I have no illumination from within the unit - board, diodes, or otherwise - so if we assume one or more of the OpAmps were installed incorrectly, what is the likelihood that the entire unit, as opposed to simply the OpAmps, is salvagable (vs replaced)?

I don't think it's possible to say with a high degree of confidence whether or not the board has been damaged, especially without having detailed knowledge of the design. My guess is that it has been, unfortunately, but I think there is some chance that it may not have been, despite Doug's experience in which it was damaged.

My one suggestion at this point is that you perform the check for illumination of the yellow LED with NONE of the suspect op amps installed. In other words, with those sockets empty. If it then illuminates, I think it would provide some degree of confidence in the integrity of the rest of the board. If it still does not illuminate, without having specific knowledge of the design and the function of the LED it would probably not be possible to draw any conclusions either way.

I have no repair shop recommendation to offer.

Regards,
-- Al

There would be a good chance that Bill O'Connell of Morninstar Audio, the Distributor of EE products, would have a competent repair facility close by if you sent the unit back. My guess is that the diagnostics would be much less time consuming, and the parts perhaps immediately available if the repair facility is tied in with Morningstar, i.e. working with them on regular basis.

If you get the unit repaired and switch to the discrete Opamps I think it will win you over despite the repair.

Hello again Al, Douglas,

Al -

No LED light. I tinkered a bit more and found that there is power coming to the board, but nothing after that (unable to trace circuits beyond taps to see where problem is). It's beginning to look like a paperweight....

Douglas -

I contacted Bill a few weeks ago about this and asked if he knew of any repair technicians that might be able to help / fix. His first response was to check power line and fuse, which I told him were fine. He then asked which OpAmps, I responded, and on his third email he stated

"...It is really hard to tell what was messed up when folks tinker with the innards of the DAC. It seems unusual that it won't even fire up. maybe a short in the power supply somewhere. Sorry I can't be of more help."

So regardless of the problem, it seems there is no one available to fix this unit, which is unfortunate. It looks like I won't be able to try those discrete Opamps you speak of.

Thank you.

I just sent Bill a link to this thread. I'm sure he can clear up the confusion.

Sorry to hear that, Dave. I still think it would be worthwhile, though, to order replacements for the parts in inexpensive form, and give them a try. Per Doug's articles the LME49710 and LME49720 should be suitable, and can be ordered from Digikey for a total of not much more than $10 for the 4 parts:

LME49710 (for U6 and U7)

LME49720 (for U1 and U2)

Hope that helps.

-- Al