MC75 Cages

Steve: Here are a couple of shots of the last one to be updated. It passed a pretty good 10K square wave, so it's ready for a music source & speakers.

Shown is detail on my wiring of the potentiometer and the front panel with the power switch and the knob I prefer (it didn't come with any knobs).

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Thanx! What would you think of upgrading the pots, or bypassing them?

I tried to duplicate the functionality provided in the original circuit, which uses the switch installed on the back of the pot. Personally, I don't see a whole lot of benefit to that design. It would simplify the circuit to bypass or replace the potentiometer, for sure.

Modifying a special amp (i.e. not the stock unit) means making some engineering choices and decisions. I thought the power switch and input grounding scheme were improvements over the stock design. I replaced the selenium rectifiers, although I wouldn't worry about them failing. I replaced all of the electrolytics, etc. What I've done some others may object to. But you've seen my work . . . I usually try to be "faithful" to a design, unless there is a clear benefit . . .
 
Steve: Here are a couple of shots of the last one to be updated. It passed a pretty good 10K square wave, so it's ready for a music source & speakers.

Shown is detail on my wiring of the potentiometer and the front panel with the power switch and the knob I prefer (it didn't come with any knobs).

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Some of the pic linx have gone skittywampus.
 
Looks pretty good for a shaker amp.:D
I admire your input wire up technique.
Anything unusual about the serial #s?
And what was with the extra holes?
 
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I think the s/n's are 0577B1 & 0574B8.

I have no idea why they drilled the holes. The plate resistors were 100 ohm vs. 220, but I put them back to spec. Everything else looks like a stock MC75, AFAIK
 
My uswag, The resistor change may have been to reduce heating at constant LF full power.
My ballpark MC50 door stop has some extra holes to mount a mic transformer.
 
Resurrecting old thread here. The reason tube cages for the vintage MC75 mono amps rarity. The only way when purchased new, was to fill in the warranty registration card to obtain them. Mine came with all paperwork from the original owner and cages.image.jpg
 
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