Terrible Crosstalk on a Dynaco PAT4

[msg1975]

So I have this PAT4. It was working fine the last time I had it in rotation. I then had it out of rotation for 6 months or more. When I went to test it to sell it, it had a hum. So I replaced the power multicap with the Frank Alstine upgrade using Nichicon KG caps. Hum went away. I put it up for sale, and sold it and the ST150.

Came back the next day with crosstalk issues. I set up a tuner and connected it to my ST150, and indeed I now have the worst crosstalk. I cleaned the input selector pretty well with F100, but it's still bad. I can't say it wasn't like that when I sold it, as I hadn't tested it for crosstalk b/c it was never an issue before.

With a tuner plugged into "tuner" on the back, the preamp turned OFF and the volume set to zero, I can still hear audio when the input selector is set to all inputs EXCEPT tuner. When I turn it on, the crosstalk is greatly reduced but still clearly audible on all inputs except tuner. It's dead silent on "Tuner" with the volume down. It's garbled on the phono.

Any thoughts on this? I'd rather not go down the rabbit hole of "UpgradeMyDynaco" as the guy still wants it and I would never get my money back out. I'd rather just fix the problem.

Thanks,
Mike

 

[ramjet]

Based on my experience with two PAT4s your problem may lie with a dirty tape monitor switch. All of the front panel switches could use a cleaning after all of these years.

 

[msg1975]

Based on my experience with two PAT4s your problem may lie with a dirty tape monitor switch. All of the front panel switches could use a cleaning after all of these years.

Wow. Good call. That seems to have alleviated the issue, although the "special" input is still acting odd. What's weird is that I had cleaned all the rocker switches already. Maybe I didn't do a good enough job on the monitor switch.