Tube Amp Rebuild (and Mod)

Step 10 First time around--' Mod A'

After plugging in a few alternate components, I liked the setup I call Mod A.

While it has a bit more sting than the the original wiring, it's also fairly clean-sounding.

Significant changes:

--Substituted a 0.1 uf bypass cap for the preamp stage. I thought this would make the signal 'muddier,' but the extra bass added something to the sound.

--Used a 20 uF cathode bypass cap for the power amp stage. This changed the response to more treble, and together with the preamp alterations help shape the sound.

The 'Mod A' circuit has a real 'bell-like' tone.

Comments

[Packerswin14]

I'm having a hard time identifying the power transformer in this amp, and it's getting REALLY hot.  The numbers are 521P1-98 839013.  The schematics don't give any voltages or info.  Any ideas?

[Pentagrid]

Hello Packerswin14, play safe & disconnect immediately. You don't say if the Transformer in your amp has been rewired as part of restoration work... if yes, check to see all the windings are connected correctly. It's possible to do this with a multimeter & a little intelligent guessing.

If it hasn't been touched, then check for a short-circuit from B+ to earth. If this proves false, there may be an internal short in the Transformer:(

But, please do take care as allowing a Transformer to run hot for any reason is dangerous, not only to you but the surrounding electronics.
John Roberts.
Wellington.
New Zealand.