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previous: Brad MB, That must be an older ... -- 5/21/2000 11:42 AM

Re: epiphone pacemaker -tubes?

5/21/2000 9:47 PM
MBSetzer	Re: epiphone pacemaker -tubes? Well, here's an update. The tubes have a date code of 1959. I also found the drawing I made when I traced out the amp, I had made a note that my Pacemaker is just like the Gibson GA-5 drawn by Joe Piazza. http://www.servtech.com/~piazza/joepage Except the Epiphone has the black lead to the speaker grounded to the chassis. Also the green heater leads from the PT go to the pilot, then a black and a brown wire carry the heater voltage to the 6V6, then the 12AX7. The black heater lead is grounded also, but generally the chassis is not used as a ground, there is a separately wired ground bus, mine is mostly white wire for the ground. The NFB lead from the OPT goes through one of the rivets holding the 5Y3 socket in (!), I have 350VDC on the plate of the 6V6, 307 on the screen, about 150 each at the 12AX7 plates. The volume pot is a 1Meg. This really won't be that bad an amp, after playing it again, I think there is still something wrong with it before it will sound stock again: probably the Astron paper cap on the 6V6 cathode is bad. I'll probably replace it with 15mf, at least 50VDC. The 470ohm cathode resistor has probably drifted too, typical champ-type repairs. I will definitely add a 1Meg to ground from pin 7 of the 12AX7, then play it like that for a while before maybe reducing the values of the coupling caps to better voice the circuit to the speaker. I was thinking of changing the 220K & 2K2 preamp resistors to the Fender values of 100K & 1K5, and maybe bypassing the cathode of the second preamp section, this would make it more like a Champ. Now I think I'll leave these like they are just to be different than a Fender. Overall the layout is very nice, since I don't need to draw the circuit on the computer, I will want to someday make a scale drawing of the assembly as a historical document of good point-to-point configuration for these excellent tubes. P.S. For Brad, it sounds like yours would have the same circuit as one of the Skylarks that's not a GA-5 type. Hope this helps, Mike

5/21/2000 9:47 PM

MBSetzer

Re: epiphone pacemaker -tubes?

Well, here's an update. The tubes have a date code of 1959.

I also found the drawing I made when I traced out the amp, I had made a note that my Pacemaker is just like the Gibson GA-5 drawn by Joe Piazza.

http://www.servtech.com/~piazza/joepage

Except the Epiphone has the black lead to the speaker grounded to the chassis. Also the green heater leads from the PT go to the pilot, then a black and a brown wire carry the heater voltage to the 6V6, then the 12AX7. The black heater lead is grounded also, but generally the chassis is not used as a ground, there is a separately wired ground *bus*, mine is mostly white wire for the ground.

The NFB lead from the OPT goes through one of the rivets holding the 5Y3 socket in (!), I have 350VDC on the plate of the 6V6, 307 on the screen, about 150 each at the 12AX7 plates. The volume pot is a 1Meg.

This really won't be that bad an amp, after playing it again, I think there is still something wrong with it before it will sound stock again: probably the Astron paper cap on the 6V6 cathode is bad. I'll probably replace it with 15mf, at least 50VDC. The 470ohm cathode resistor has probably drifted too, typical champ-type repairs.

I will definitely add a 1Meg to ground from pin 7 of the 12AX7, then play it like that for a while before maybe reducing the values of the coupling caps to better voice the circuit to the speaker.

I was thinking of changing the 220K & 2K2 preamp resistors to the Fender values of 100K & 1K5, and maybe bypassing the cathode of the second preamp section, this would make it more like a Champ. Now I think I'll leave these like they are just to be different than a Fender.

Overall the layout is very nice, since I don't need to draw the circuit on the computer, I will want to someday make a scale drawing of the assembly as a historical document of good point-to-point configuration for these excellent tubes.

P.S. For Brad, it sounds like yours would have the same circuit as one of the Skylarks that's not a GA-5 type.

Hope this helps,
Mike

Replies:

Paul C FWIW the guy brought in the amp tod... -- 5/24/2000 12:14 AM