EE Minimax DAC 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

I'm just not sure what I can do for you. Tech repair is expensive,time and trouble shooting to find what went wrong in your op-amp swap. Then replacement parts and putting it all back together.

I have a couple new in box older DAC's not the DAC PLUS that I could let you have for my cost.Probably would cost about the same as doing a repair or a few dollars more. As I saved a couple of these just in case something went wrong with somebody's original DAC if my customers. It is an original DAC correct? Have to ask, did you purchase from me or second hand? Let me install the Dexa's though if considering throwing them in yourself.

Hope that helps,
Bill

Hello Al and Bill,

Al -

Thanks for your optimism. At this point I think I'm going to shelve the project, perhaps attack with new vigor at some point in the future. I've already spend quite a bit of time trying to figure this out and it's probably best to take a break and put some energy into other things.

Bill -

Thanks for your offer. Since it sounds like buying new is more practical than trying to fix (if possible) we then venture into "which one do I want" territory. I think there can be a case for this unit, the DAC Plus, or a number of other units (Metrum seems to be getting some A'Gon press). The problem for me is that my "discretionary spending" is not what is was a few years ago, and my original hope with the Opamp upgrade was to tie me over until things change (financially), then see what's on the market.

Perhaps we can speak again in a few months?

Thanks to all.