Pioneer A-9 Resurrection

[mpr2000]

So after a long battle with an A-9, I am finally nearing success. This one had bad outputs on one channel, drivers and a host of other supporting components fail. IE, the regulator board, etc.

So after lots of work, I am out of protection and critical voltages look okay. I am now on to the amp idle adjustments and I have a two questions.

Topic note: The pots for idle current adjustments were bad. Those have been replaced with multi-turn pots.

Question 1: The procedure for each channel indicates where to measure from (21 and 20 for the left channel), but has two pots. For the left channel procedure, should I assume I want to adjust VR1 for 50mV, then adjust VR3 to arrive at a final setting of 75mV?

Second question, the procedure above states to rotate pots to fully counter-clockwise position. The old pots read Zero ohms in this position. I assume this is accurate and a 'short' at VR2 and VR4 in the schematic below is appropriate to start adjustments?

 

[QSilver]

Question 1: The procedure for each channel indicates where to measure from (21 and 20 for the left channel), but has two pots. For the left channel procedure, should I assume I want to adjust VR1 for 50mV, then adjust VR3 to arrive at a final setting of 75mV?

Yes

Second question. power it up on a DBT if your in any doubt. If you can set it with the DBT then reset your adjustments back to 0 and then do it agian without the DBT.

If anything goes wrong, the DBT will give you some "leeway" if anything goes wrong.