Friday, December 10, 2010

The other amplifier

I've started to take a look at the other amplifier which is more different from the first amp in that it is really two amps in one with one 12AX7 and two 6L6's for each amp. One amp feeds the output transformer on the top of the case (pedal) and the other amp feeds what appears to be a smaller output transformer inside the case (manual). The caps at the right hand end are multi-sectioned 40 / 40 @ 450v and a 100uf @ 50 volts.

Here is the top view. You may click on the image to enlarge it.
The view of the guts.
The right hand end. The transformer is the output transformer for the manual speaker. There is also a relay at the right hand end and I haven't worked out what it is for yet.
The middle. To the left is the choke.
The power transformer and the choke.
I found this schematic somewhere. It shows 7027 tubes being used instead of the 6L6's for the pedal amp. On my amp, I suspect the cathode caps for the 6L6's are the 100 uf 50 volt sections on the top mounted multi-section caps. The Sangamo coupling caps are 0.1uf 600v. The 10 watt green cathode resistors are 250 ohms for the manual amp and 200 for the pedal amp.

On one of the 6L6's for the pedal amp, there are 24.5 ohm resistors connecting pins 2 and 7 (heaters) to ground.

Below are photos of two more schematics.
The schematic above appears to be the same as the version above and may be easier to read.

The schematic above is similar but different in that 6L6's are specified for both pedal and manual amplifiers and the use of 1k grid resistors which I presume would be carbon composition. The coupling caps are shown as 0.022uf but I wonder if they are really 0.22uf.


No comments:

Post a Comment