Need Help with Squealing

[valboschi]

Hi

Here's my highly valued 18 watt combo I made ages ago.

https://youtu.be/of_xEvs6bKM?si=7lUOjOcSLb0mT456

Current problem I have and need help with if possible...I use the normal channel so 1 ecc83 is removed but on the normal channel if there is no input in the jacks, when the tone pot is moved to zero I get an extreme squealing , which goes if I turn the tone control up.

Any pointers greatly welcome. Thank you.

[Daviedawg]

Welcome to the forum. Your amp sounds great.

When you do have the trem channel operational does that squeal as well, or only the normal channel?

Squeal is usually associated with lead dress causing oscillation. If only the normal then I suggest you try chopsticking the lead dress around the preamp valve and controls. If both then it may need a more extensive search.

If you do not get an improvement from this simple approach then come back including the schematic you built it from for more advice.

Good luck

Dd

[valboschi]

Superb, thanks Davie

I need to put a valve in the trem channel and try it... I'll post a couple of pictures soon also.... i suspect my wiring might be needing help, and I remember that recently I moved the el84s so i could fit a celestion blue in the cabinet, because the magnet got in the way of the 84s....I actually rejected the Blue in the end for the g12h I normally use.......I do love this amp still....

but it seems only to happen when there's nothing in the normal channel inputs and the tone control is at zero... which is easy to avoid..... but I'll love it if I can fix it..... I'll check those leads, thank you

I'll go in and look.

[valboschi]

I just shot a quick video

https://youtu.be/V5DEkJWhejw?si=FH4iB6Ud-_mdqIjy

[valboschi]

It was a board from Ceriatone, so I think it's from his schematic and layout, from what i can see, it's the same. Nik kindly made me the board with old mustard etc components.

[Bieworm]

When you put the tube back in the socket, does it work like it should of is there something off?

[valboschi]

Thanks very much, here's an update, things happened before i got to put the trem tube i and try, but thank you. ..

I decided to test some voltages.... I put the tester neg to ground and the tester pos to the positive of the large board mounted electrolytic.... the EZ81 valve started arcing, then the main amp fuse blew......

I found another fuse. Started the amp up again. The same EZ81 arced then blew the fuse, again. Unsurprisingly.

I went to Cricklewood Electronics and bought some new 1A Sloblo fuses, and a fuse holder.... I drilled the chassis and put in the fuse holder to house a 500mA fastblo to connect between the transformer centre tap and earth.... then I replaced the 1 Amp Sloblo Mains fuse.

I replaced the ez81 with an old Sylvania that used to be in the amp before I recently upgraded that to a Harma Retro EZ81 (the one that arc'd).

So with this done the amp seems working fine, and the issue with the squealing isn't happening..... SO FAR!

Wish me luck as I go on my way