Distorted squished tone from amp

[MattB930]

Hello everyone, I am having trouble finding a schematic for an Alamo Electra All-tube amplifier. It has 4 inputs, 1 channel with volume, tone, speed and intensity for vibrato; and the other channel has volume, tone only. 4 12ax7's 2 6v6's 5ar4 rectifier.

On either channel when I turn volume up to lets say, 5, it gets really crunchy and breaks up way earlier than I think it should. I've worked on a blackface electra with a SS preamp and same dual 6v6 output and it sounds incredible but this one(only difference is SS vs. tube preamp) just gets this squashed distorted tone. It is like it is being restricted or something is overloading somewhere.

The amp's power tubes are biased at about 7.94watts, 320v on plates, 19v cathode with shared cathode resistor of 360ohms.

Before I start digging around the preamp section is there anything I should be checking first?

thank you for the help.

[faman777]

Tube Vs. SS preamp

Does the amp with the SS preamp also have a tube rectifier? These old Alamo amps generally have a lot of compression when driven hard and if your caps are going bad, it could also have a lower clean output volume(headroom), but that just may be how it's supposed to sound. By that I mean it's an old amp and an old design vs. newer amp newer design.... something like the tweed era fenders compared to the solid state rectifier fenders made later in the 60s. I have owned and worked on a few of these old Alamo amps which were made right here in San Antonio. I have schematics for several of them(not that model) wish I could be more specific about your particular issue, The Alamo Champ clone, Challenger Model,1 X 12AX7, 1 X 6V6, and 5Y3 rectifier begins to break up at about 4 and then overdrive and compression take over, but it sounds good like that. I have a schematic for the Montclair model which also has trem and 2 X 6V6 power section with 4 X 12AX7 preamp tubes and a 5Y3 rectifier. email me if you want it.... tubeampman@rocketmail.com fa

[MattB930]

It doesn't have a tube rectifier on the SS electra. I emailed you by the way.