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'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.

Hello Douglas, Al, and Mofi,

Thanks for your time and energy.

Although I recall seeing the "squares" on the NE corners of the OpAmps after initial inspection, I can no longer rule out the unlikely. 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 realize more trial and error might be necessary to answer this, but my time to do so grows short (honey-dos, kids, etc.). Is there a qualified technician / repair shop that might be able to further diagnose / fix this - I have been unable to locate one?

Cheers.

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.