50w with Drake 1202-133 PT

[janarn]

I have a 50w with this PT. I'm very interessted in som info of this PT.
This PT is not on the transformer list at Marstran.
When was it introduced? Voltage? How is the quality?

[Brian Wallace]

The PT can be found on my historic data base page.

This PT came to be around 67, it has the same plate voltage as the JTM45 but the current capability has been upgraded for the EL34's. Same quality as any Drake PT.

[janarn]

Yes, I have seen it on your historic data base page, but not on the current transformers codes. It's a little confusing where to place the 1202-133.
It came after the 1202-55. But did it come earlier than the 1202-118?
Does the 1202-118 have heater output for the tuberectifier like the 133?

[Brian Wallace]

Yes, the 1202-118 has the 5V tap for the tube rectifier. This was removed around 74 / 75.

[Baron74]

I know this thread is old but i have been trying to find out some info regarding this. I want to do a 1202-55, 784-139 el34 combo (tube rec) and i was wondering, would i see the same/similar plate voltages as a 1202-133? I have had it in my mind that maybe the unloaded voltages in the 133 maybe a little lower than 350-0-350? Can anyone comment on this.... i have a keen plan to do a 67 ish build that i habe seen in amp archives, 1202-133, 784-139, el34 tube rec, jtm45 tone stack 270 mix resisters, dual 32uf preamp filtering ...

[neikeel]

Is it the higher B+ you are after? The 1202-118 works very well with a JTM50 set up (as does the 784-139OT) although I prefer mine with the -128OT which uses 270k mixers and single 32 uF preamp can.
The JTMs that I built as clones sound best with dual 32 can, 470mixers with 500pF cap, stock tone stack and 100pF on vol pot.
An amp of the spec you describe would probably be the white one which is a PA (S10612)?
What you describe is an unusual mix, just wondering what you are after?

[Baron74]

Thanks N. I have actually built a black flag type build with marstrans and used the 118. Very nice. For fun i have been experimenting with some of thecombos that I have seen in amp archives. All very interesting all the little differences. I was just wondering if the 1202-55 would yield the same plate voltages as the 133 using el34s. So.... last night i made a transformer swap. I put in a classictone 1202-55 that i had on hand. As per photos i had seen i changed mix resisters to 470s the preamp is dual 32 as per pics. Bit hard to see other filtering but i used 32uf for screens and pi, and 32 for mains... was going to put an f&t 50uf on but i think 32 should be fine, think 40 uf is the actual spec. I am getting 470 on the plates. I am using 240 wall voltage. Is this in the ballpark or maybe a little high? I am going to take it to the rehearsal room see how it sounds.

[Baron74]

Btw cant remember which photo it was. I do know i have seen a couple under the 50 watt section, there is a couple in the 67/68 year with jmp faceplates and black flagish specs...some do have the 118 and he 133. I am using the marstran 139 btw. I will let you know how it sounds. I presume it will yield more clean head room. Did jtm45s with kt66 ever get plate voltages in the 470 region?