Tybe radio conversion to guitar amp

[nosaj]

You could inject signal at the grid of v4, but first I guess you should test the speaker with a AA bather for clicks.

nosaj

[gilmo789]

In the instruction manual, which is found in the link above, there's a list of voltages taken at various points of o the circuit. I measured the rectifier AC input and DC out and it's in the right ballpark. A bit lower but I put that down to the LBL. Is there a test I can do other than verifying that it transforms?

[nosaj]

before you spend any money on it check the transformers first.

nosaj

[gilmo789]

ANy reason to ditch the probably working existing power amp?

Probably needs more gain than the single triode, but the tube just before is a pentode. WHy not try to get that to sound good?

That's the spirit!
I thought triodes made decent preamp tubes, is this not the case?
I haven't got the thing to make any noise yet, The caps are all measuring in the pF range but the rectifier works and the tubes light up. I tested the existing tubes for shorts and they seem OK in that regard.

I think I can recap it for a small amount of money, There's only 10 in the amp circuit.

I'll see what happens!

[Enzo]

ANy reason to ditch the probably working existing power amp?

Probably needs more gain than the single triode, but the tube just before is a pentode. WHy not try to get that to sound good?

[g1]

6SJ7 6v6 5y3
Fender champ 5c1

nosaj

I think his 5Z4 rectifier should work ok in there.

[nosaj]

could I do that with the existing tubes?

6SJ7 6v6 5y3
Fender champ 5c1

nosaj

[gilmo789]

could I do that with the existing tubes?

[nosaj]

Tear it all out and make a fender champ amp.
nosaj

[gilmo789]

I got myself as old 5 tube radio which I reckon I can convert into a 5ish watt guitar amp. It's just the chassis so I'm not destroying anything. The valves light up when I plug it in (LBL used).
This is the exat thing: http://kbmuseum.org.uk/kb_images/ar30/ar30.htm

I reckon I can get rid of most of the radio kit but I'm wondering if there's any pitfalls ya'll can foresee before I get going.

I've got the circuit diagram and I've greyed out everything that's not the amp, It's got a line i and a speaker out. Most of the parts are in good nick but I'll certainly need to recap it.

One thing I'm not sure of is the preamp tube is a double diode triode (V3). Can I just use this as a triode or do the diodes need to be dioding?

Thoughts?

V3: 6Q7G (double diode triode)
V4: 6V6G (pentode amp)
V5: 5Z4G (rectifier)