EE Minimax DAC repair

I have no particular familiarity with the Minimax, but as an electrical design engineer, and after looking at the pin configurations of these devices (shown on page 3 here and page 5 here) I believe Doug is absolutely correct. Inserting either of these op amps oriented the wrong way is a disaster, which will almost certainly destroy the op amp, and probably damage other devices on the circuit board that connect to it, and possibly also those that supply power to it.

10-15-12: Daveaudiony
Both original OpAmps and proposed, regardless of position / orientation, do not change the outcome - unit no longer powers up.

This seems to say that you have tried both the original and the new op amps with both orientations. If so, all of them are almost certainly destroyed. If you are not certain that you used the correct orientation when you first re-tried the original op amps after noting the problem with the new ones, it might pay to obtain replacements (for either or both sets) and try again, in the off chance that other devices on the board were not damaged.

Also, be sure to follow good anti-static practices when handling these devices. As a minimum, that means touching a grounded metallic structure immediately before handling them, avoiding contact between your fingers and device pins (perhaps using a DIP puller to handle the devices), and not working where carpets or other static-prone surfaces are present.

Regards,
-- Al

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

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