Nick;
That's quite a collection: have you ever tried to estimate how much those instruments would cost if you'd bought them new? (or perhaps you did!)
Refugee:
If you have one channel of your 7A26 working, I'd suggest you plug it into the LH slot of the main-frame with the LH side-cover removed. You can then check the AC and DC's of the two channels with, say, a 40mV p-p signal applied to both and the inputs set at 5mV/div. You should get close to 40mV p-p out of the FET follower (R150)*. By progressing down the signal path you should find where things have gone awry. Most problems with my Y amps have been associated with the input attenuators, and in two instances, a bizarre component failure whereby a small white tubular ceramic capacitor (c 2pF) has grown to about 10x the value!
John
* if not, there's an issue right up front!
Quote:my shack test bench
That's quite a collection: have you ever tried to estimate how much those instruments would cost if you'd bought them new? (or perhaps you did!)
Refugee:
If you have one channel of your 7A26 working, I'd suggest you plug it into the LH slot of the main-frame with the LH side-cover removed. You can then check the AC and DC's of the two channels with, say, a 40mV p-p signal applied to both and the inputs set at 5mV/div. You should get close to 40mV p-p out of the FET follower (R150)*. By progressing down the signal path you should find where things have gone awry. Most problems with my Y amps have been associated with the input attenuators, and in two instances, a bizarre component failure whereby a small white tubular ceramic capacitor (c 2pF) has grown to about 10x the value!
John
* if not, there's an issue right up front!
Radio Museum collection: Here
