Ty_Bower wrote:Get out a printed copy of the circuit board diagram and the parts list. Go through with your ohmmeter and measure every resistor on the board. Cross them off as you verify each is correct. It should go without saying, but the amp needs to be powered off while measuring the resistors. You may as well pull out the tubes, too. A few resistors might be impossible to measure while in the circuit, since they may be tied to ground in more than one place.
While you have your ohmmeter out, measure the DC resistance of the primary side of each output transformer. Measure from plate to plate, and also from each plate to the center (red) lead. For Dynaco transformers, it is normal for the measurement from plate lead to center lead to differ on each side of the same transformer. The measurements of the left channel transformer should be similar to the right channel.
Post any measurements which look suspicious. If all the ohm readings appear normal, then it will be time to move on to working voltage readings.
I had the amp on so I thought I'd take a few preliminary voltage measurements.
J13= 0V same a left channel
J21= 40.3V close to left channel
J22= 36.5V same as left channel
J23= 37.4V very close to left channel
Right 12UA7:
1= 240V close to left channel
2= 0V same as left channel
3= 10V same as left channel
4= 3.06Vac (left channel = 3.23Vac)
5= 3.06Vac (left channel = 3.23Vac)
6= 245V very close to left channel
7= 0V same as left channel
8= 10V same a left channel
9= 3.23Vac (left channel = 3.08Vac)