5F1 clone squeal

[zlanderous]

Hi,

This is my first amp build so I don't quit know what's wrong. I got the parts for a 5F1 champ clone separately (not in a kit) but got off brand transformers. All the voltages look good but everytime I turn the volume up, once I get past the midpoint on the knob the amp starts squealing very high pitched and I can hear the output transformer whine as well if I listen closely. I tried disconnecting the negative feedback loop but it doesn't change anything, I also tried swapping the cables on the primary of the output transformer but that didn't change anything either. So in the end I bought a Hammond version of the output transformer but that doesn't change anything. Anyway sorry for the novel :p anyone know what might be the root of the problem?

Any help would be greatly appreciated

Luc

[Willabe]

You might have something mis-wired, wrong part value or both. Look at this link for a great way to double check an amp build. When you go through the build also double check all resistors and caps for correct values.


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

[shooter]

Does it squeal with no guitar plugged in?

what's your skill level for working with HV? 

squeal could be positive feedback from crossed wires, wrong value components changing tube gain and many other suspects.

I'd start powered OFF, discharged, and verify your R values.

IF, you are competent and safe, measure all your tube pin volts and post them.
With power STILL ON, carefully *chopstick* your wires and see if/where it makes a difference to the squeal.

My 1st 5f1 squealed also, it was poor wiring and not measuring resistors before I soldered them in.  Take your time, be patient and you'll be working soon enough