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Help needed to debug QRP-02

Started by jamh, January 21, 2013, 07:43:58 PM

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peranders

If you look at the schematics you see that the 12 V is for the opamps only. The opamp is OK? Do you have the polyester caps on the solder side?
/Per-Anders Sjöström, owner of this forum

Homepage with my DIY hifi stuff

jamh

Yes, the caps are on the solder side.  Perhaps the opamp is not ok.  How do I tell without removing it?

peranders

Check first that you have mounted in correctly, then you can measure the resistance between pin 4 and 8. If it's blown I'll you should measre near zero ohm.
/Per-Anders Sjöström, owner of this forum

Homepage with my DIY hifi stuff

jamh

I think we're on to something.  While res between 4 and 8 is good in both (18.k), I started measuring all the pins and there is something not right between 7 and 6 in the one with the blown traces.  I measured 140ohm between outb and -inb.  In the good one this is 2.3M.  Time to take out the AD8620?

jamh

C6 is also blown. It shows 140ohm as well.

peranders

C6, is it measured only this or in circuit? The opamp seems to be broken.
/Per-Anders Sjöström, owner of this forum

Homepage with my DIY hifi stuff

jamh

#21
In circuit, but in circuit, the value of C6 in the other channel was in the Ms. I'll change them anyways while I'm at it.  Got some nice sounding wimas.

jamh