Alamo Model 3?

[lowell]

Has 2 6SC7 preamps, 2 6V6, 5Y3 rectifier.

Just curious how the OT is wired. This thing has been rewired like crazy and is super dusty. Hard to see what's going on. I can start disconnecting things and figure it out, but a schematic would help. There aren't any online anywhere for this model.

[lowell]

Well still like to see one, but I got it figured out. Wow, this speaker is amazing!! Sounds incredible! Jensen Alnico 5 PM Speaker. Says Chicago on it. I was making sure the speaker was good with another amp output... wow.

[vintagekiki]

http://www.tdpri.com/threads/confirming-tube-line-up-for-alamo-model-3.318905/


Alamo 1948 amp 2 and amp 3 schematic

[lowell]

I saw those. Different amp. This has 2 6SC7 pres and 2 6v6...and 5y3. Thanks for posting.

[vintagekiki]

If you do not know the model of your amplifier set the picture to facilitate our search for

[Chuck H]

This thing has been rewired like crazy...

Are you certain that it ALWAYS had two preamp tubes then? Any signs that one was added rather than stock?

[lowell]

It looks to have been built this way. I have straightened out the OT wiring, and have replaced all the electrolytic filters. Was hoping that'd fix the stability/oscillation issues but alas. It helped, but it's still there. I don't have a schematic so I'll need to do some circuit tracing and also see how 6sc7's are biased.

[lowell]

The amp is working but is unstable. Turning the tone control or even sometimes touching the tube socket pins causes the amp to oscillate and squeal. When playing guitar thru it it sounds like a bad speaker, real buzzy and super crappy sounding. Tried another speaker and same result. There is about 340mv on one of the 6v6 grids and about 100mv on the other, so I'm thinking the coupling caps are leaky. Would you all say that leaky caps could cause such symptoms?

[lowell]

I'll take a shot at this one: Yes. I replaced the coupling caps and it's fixed. Grid voltage on the 6v6's is gone and symptom is gone!