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Old 27th July 2012, 01:46 AM   #21
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Yes, I only have 8.9v on Pin 8.

As far as the voltages on the op amps, the only one I see is on the upper left of the board. 8 pin IC. The dual op amp has the same voltage on pin 6 as pin 8 of the other IC.

These are the voltages I found from that IC:

Pin 1: 0.051 *
Pin 2: 115.9
Pin 3: 116.1
Pin 4: 0.044 *
Pin 5: 0.001 *
Pin 6: 8.9 *
Pin 7: 0.095 *
Pin 8: 14.00

Again the "*" means voltage was fluctuating

Could you please point me to the proper "small transformer" I should be using the center tap to check to neg rail? thanks.
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Last edited by Deadly Sones; 27th July 2012 at 01:50 AM.
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Old 27th July 2012, 01:52 AM   #22
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The small transformer is the one near the power supply driver board.
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Old 27th July 2012, 01:58 AM   #23
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When I place one prob on the center tap of the small transformer, and the other on the neg rail it reads 0.000v but flickers between OL and 0.000ohms repeatedly.
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Old 27th July 2012, 02:14 AM   #24
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Not sure how relevant it is, but when I bought this amp it only had a few power supply transistors (no outputs at all) and these two driver transistors were shorted. I replaced them (in the yellow square) and checked all the resistors and the power supply appears to have powered up and it stopped going into protection. Could I have missed something when I did this repair? I know R4 looks smoked but it has proper resistance.
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Last edited by Deadly Sones; 27th July 2012 at 02:16 AM.
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Old 27th July 2012, 02:42 AM   #25
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I don't know what #23 means because I don't know how your meter responds. Find a way to determine definitively that one of the secondary center-taps for the small transformer is directly connected to the negative rail.

If you have a scope, make sure that you have oscillation on the tabs of the two FETs for the small transformer. It should swing from ground to ~24v.

I can't read the circuit boar designations for the drivers you replaced so I don't know what they're used for.
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Old 27th July 2012, 09:35 AM   #26
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K. I'm going away for the weekend so I'll continue this next week. Thanks for all your help Perry. To be continued....

The circuit designations for them two transistors is QP2 and QP4.
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