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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
almarg's avatar
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almarg
9,670 posts
 
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
morningstaraudio's avatar
morningstaraudio
154 posts
 
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
daveaudiony OP
5 posts
 
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.
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