1965 Supro Amp

[Doc Stitches]

2 questions ( see photos )


1.....What model is this amp ? 3 / 12AX7, 2 / 6L6, 1 / 5Y3 ( I can't find a schematic with 3 / 12AX7s )


2.....No sound at all coming from the amp, either channel ..... all tubes light up. I tried a different speaker.

[madkatb]

If that's a 15" speaker, try S6497T

[Doc Stitches]

Supro 6497 T schematic

If that's a 15" speaker, try S6497T

Where can I get a schematic ? All the usual searches have turned up nothing

Thanks
Doc

[Jazz P Bass]

Here is the 6420T.
3 12AX7, 5U4 & 2 6L6.

Supro_6420TR.zip

And the infamous Jimmy Page amp, the 1690T.

Supro 1690T.pdf

[madkatb]

http://www.dirtygirlamps.com/Amp_sit...iles/1690T.pdf
Should be close. Has two 6l6's. One site cross referenced the amp as a 1697t, Thunderbolt combo tremolo.
(Or you could send me the amp and I'll draw up a schematic for you. )

[EFK]

Not a 1690, that's definitely a 6497, the all-purpose accordion/bass/guitar amp. The 5Y3 is wrong, don't know why someone stuck that in there but it should be a 5U4. 100%, not even a question.

[Doc Stitches]

Here is the 6420T.
3 12AX7, 5U4 & 2 6L6.

[ATTACH]35164[/ATTACH]

And the infamous Jimmy Page amp, the 1690T.

[ATTACH]35163[/ATTACH]

Thanks Jazz P Bass ... Am I missing something ?.....the 6420TR schematic shows only 2 12AX7, not 3

Are we saying there is no schematic for the 6497T ?

Maybe I won't need one but it would be nice to have.

Thanks
Doc

[Doc Stitches]

Thanks for the offer madkatb. Maybe I'll drive it up to Canada on my lunch break tomorrow

Doc

[Doc Stitches]

EFK ..... was there ever a schematic for the 6497 ?

Doc

[madkatb]

Sure. I'm guessing you'll be staying the night so what kind of beer do you like?

[EFK]

I drew one out the last time I had one here but it's just hand sketched, I haven't converted it over to a 'nice' schematic like the others. If I can find it and it's readable I'll scan it and post it. These are not my favorite amps, in fact the first one I had a few years back had all kinds of weird problems and I finally just gutted it and built something else into it. I've worked on a few more since; assuming you know for certain that your tubes are good and you're getting juice to the preamp and the output, the first thing I would check is the output cable to the speaker. Make sure the cable is functional, make sure the speaker is not blown and then - REALLY IMPORTANT - make sure the socket for the output cable has not corroded or cracked and subsequently is grounding the positive to the chassis. The 'socket' is just two square pieces of garolite or whatever with two tabs for the cable pins and the whole contraption is riveted to the chassis. They went from real 4 pin sockets to these around 1962-ish or so, and I've had a couple that were cracked and grounding out the speaker output.

[Doc Stitches]

Sure. I'm guessing you'll be staying the night so what kind of beer do you like?

I'll have to take a rain check on your hospitality madkatb......a very generous offer

[Doc Stitches]

EFK

Thanks for the pointers. I will follow them in order.

First thing I need to get today is a 5U4 ............. I thought the socket stamp was 5Y3 ( light rust made it impossible to be certain )

The chassis design does look a little on the "cheesey" side.

[Doc Stitches]

EFK

Thanks for the pointers. I will follow them in order.

First thing I need to get today is a 5U4 ............. I thought the socket stamp was 5Y3 ( light rust made it impossible to be certain )

The chassis design does look a little on the "cheesey" side.

Hey EFK ... you were right ... speaker cable was grounding positive to chassis. Still checking other stuff......

at least it looks like no one has been in the amp.

The 15 in. speaker is only reading 7.6 ohms ... is that an issue ?

[Doc Stitches]

I disassembled the female speaker socket and both socket clips ( black and green wires ) are grounding out, even with them removed from the

chassis.

Does this mean I have a bad OT ?