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KepCo/6550 Questions

12/1/1997 4:33 PM
Craig	KepCo/6550 Questions I just acquired a KepCo voltage regulated DC power supply that I plan on converting to a Marshall, Ampeg, or? It uses a 5U4 and a duet of 6550’s, and has 2 9-pin sockets, and 1 7-pin (which I will most likely expand for 9-pin. I was really excited to find that the 5U4 and 6550’s are Tung-Sol’s (that are in near mint shape!). There was a single Amperex 12AX7 also: never seen this type before – it has a cool little trumpet player silk-screened on it. : ) Any way, I have a couple of questions: 1) Any recommendations for good 6550 designs? 2) What are some of the attributes that make the 6550’s unique/desirable vs. EL34/6L6? 3) The P.T. has 3 distinct 6.3v taps. Why 3? All the schematics I’ve seen for guitar amps don’t reference more than one pair of leads for all 6.3 filaments. Is this specific to a voltage regulated DC power supply circuit? 4) Anyone familiar with KepCo? The components and workmanship of this unit are of a very high quality. 5) The way this unit was laid out, the tubes are all in a row, but the row is slightly off-center, rather than close to the rear panel, as in most Fender designs. It used a vertically mounted, all pt. to pt. Eyelet board, positioned between the tubes and the rear panel. Is there any reason not to use this vertical arrangement? It was wired so that all the caps were on the rear panel side, and all the resistors were on the tube side. Thanks, Craig

12/1/1997 4:33 PM

Craig

KepCo/6550 Questions

I just acquired a KepCo voltage regulated DC power supply that I plan on converting to a Marshall, Ampeg, or? It uses a 5U4 and a duet of 6550’s, and has 2 9-pin sockets, and 1 7-pin (which I will most likely expand for 9-pin. I was really excited to find that the 5U4 and 6550’s are Tung-Sol’s (that are in near mint shape!). There was a single Amperex 12AX7 also: never seen this type before – it has a cool little trumpet player silk-screened on it. : )

Any way, I have a couple of questions:

1) Any recommendations for good 6550 designs?
2) What are some of the attributes that make the 6550’s unique/desirable vs. EL34/6L6?
3) The P.T. has 3 distinct 6.3v taps. Why 3? All the schematics I’ve seen for guitar amps don’t reference more than one pair of leads for all 6.3 filaments. Is this specific to a voltage regulated DC power supply circuit?
4) Anyone familiar with KepCo? The components and workmanship of this unit are of a very high quality.
5) The way this unit was laid out, the tubes are all in a row, but the row is slightly off-center, rather than close to the rear panel, as in most Fender designs. It used a vertically mounted, all pt. to pt. Eyelet board, positioned between the tubes and the rear panel. Is there any reason not to use this vertical arrangement? It was wired so that all the caps were on the rear panel side, and all the resistors were on the tube side.

Thanks, Craig

Replies:

Dave Harris "3) The P.T. has 3 distinct 6.3v ta... -- 12/2/1997 3:19 AM