[averydonovan]

I try bridging the connection with my meter, but the amp won't power up.

My first readings of the problem came from the end of a mini-to-mini cable plugged in, but my 200mV rating is from pin 3 to pin 6. I have also measured from pin 3 on the OPAG to pin 6 on the BUFG with the same results.

And I am happy to report that I have solved the problem thanks to the person who emailed me. He suggested that I lift pin 5 since it was connected to the negative power rail. On the datasheet, pin 5 is for offset trim adjustment on the OPA627 and my offset was actually a negative amount. I lifted pin 5 and voila! Between pin 3 of OPAG and pin 6 of BUFG there is 0 offset now. Thanks very much to the gentleman who emailed me, and thanks tangent for your help. My amp is now in fully working order

Edit: I also posted this info on my site on the page about my PIMETA so hopefully others can avoid this same problem: http://www.donovansmith.us/content.php?article.21

 

[tangent]

Quote:

I try bridging the connection with my meter, but the amp won't power up.

Then you're either using the meter wrong, or the ammeter section fuse is blown.

Quote:

My amp is now in fully working order

Good to hear it. I'll have to mention this in the docs...

 

[00940]

donovan, I'd kiss you twice if I could

I just finished a pimeta and had big offsets values (like -54mv in both channels). Just lifted a pin and I'm at -0.1mv and 9mv which is far better.

The pimeta is a nice sounding amp btw.

Mine has an opa2132, an opa604 for ground and simple buf634. Resistors matched as close as possible (as close as my DMM authorized me), alps pot, 6.8uf wima caps and 4x220uf Elna Cerafine. Input caps are 0.22uf audyn mkp. It's powered by a small homemade PS, with an external 15V ac-ac transformer, rectification by schottky, then 3x2200uf (common caps, all bypassed by 0.1uf wima), lm7815 and one more 2200uf.

Only one little problem : the holes for C1 are too small for good mkp caps. I had to reduce in diam. the leads of my audyn

I will only keep a week since it's an order. Selling it at real cost, it's at about 110-120€.

 

[averydonovan]

Glad that this thread helped someone else with the same problem. Just wait until you build a PIMETA with OPA627s, then you'll not want to let that thing go