After a year and a half and 3 other amps I finally got my express to work but now it has a high pitch squeal....it squeals regardless of volume. I cant even bias the amp cause of the sequels. For some reason I thought this would be a great first project -horrible mistake.
Could it be the fact that the shielded piece of the wire coming the plate of tube 1 to the input jack gets grounded to the input jack?
No idea, any help would be great!
Done! (almost) after a year and half High Pitch Squeal
Moderators: pompeiisneaks, Colossal
-
martin manning
- Posts: 14308
- Joined: Sun Jul 06, 2008 12:43 am
- Location: 39°06' N 84°30' W
Re: Done! (almost) after a year and half High Pitch Squeal
This may be easy... have you tried switching the primary wires on the OT? If you get this wrong, NFB turns into PFB. If that's not it, try pulling tubes beginning at V1 and see if and where it stops.
Re: Done! (almost) after a year and half High Pitch Squeal
Yep the first thing to check would be the OT primaries. They are might be backwards. Next check you cathode grounds on your preamp. Then forget about the shield being attached to the plate on V1 for now and only ground on the input jack side. That is dangerous to be doing for a first build.
Re: Done! (almost) after a year and half High Pitch Squeal
When you say "plate" do you mean a grid pin on the socket or a plate pin on the socket? (pin 7/2 or pin 6/1 ?)yalesmith wrote:....Could it be the fact that the shielded piece of the wire coming the plate of tube 1 to the input jack gets grounded to the input jack?.....
If it says "Vintage" on it, -it isn't.
Re: Done! (almost) after a year and half High Pitch Squeal
yup that's why I love this website...a dumb mistake but probably would have took me days to figure out i had the OT primaries reversed....I had really love this amp so far...I am so proud just really happy....I need to test tubes....I wish I hadan rca blackplate but I do not...I do have a bugle, old toshiba...and a bunch of reissue mullard and tungsol.