squeal

[isaac_teller]

Hello. I built a DIY clone of a Fender Deluxe reverb. after powering up there was a high-pitched squeal. I switched tubes, reversed output leads but the squeal persists. I removed V1 and the squeal is still there. If I turn the master down(Frondelli master volume) it cuts off the squeal. Any suggestions of what to try next?

[SILVERGUN]

https://el34world.com/Forum/index.php?topic=17701.0

[tubenit]

When you say you switched tubes,  did you change ALL the tubes for known good ones?

What are the voltages?  What do you have the tubes biased at? 

Can you post a hi-rez picture of the chassis interior?

Did you try disconnecting the NFB?

Did you try pulling one tube at a time and also jumpering over gain stages?

with respect, Tubenit

[isaac_teller]

Yes, I changed all the tubes for known good ones. I will check voltages and post later. As for a picture, I don't have a smartphone, I'll have to ask a friend to photograph.

[shooter]

does the amp have NFB?, if so, disconnect and see

[isaac_teller]

I also disconnected the NFB. Didn't help.

[sluckey]

Hello. I built a DIY clone of a Fender Deluxe reverb. after powering up there was a high-pitched squeal. I switched tubes, reversed output leads but the squeal persists. I removed V1 and the squeal is still there. If I turn the master down(Frondelli master volume) it cuts off the squeal. Any suggestions of what to try next?

Please provide a link to the schematic/layout you used. Also provide some info on the frondelli master volume. Maybe even remove that frondelli to see if it is the problem.

Pull the PI tube. It's the 12AT7 closest to the 6V6s. Squeal stop?

[isaac_teller]

https://www.tdpri.com/threads/removed-the-master-volume-on-my-81-vibrolux.735213/
Post #5 has the Frondelli schematic. When I get home I'll pull the PI tube.
http://www.prowessamplifiers.com/schematics/fender/deluxe_ab763_schem.pdf
Here's the schematic