Marshall 1962 Bluesbreaker (JTM 45) Reissue Hum

[ca7922303]

Look at the schematic in the link.
Middle lug (wiper) goes to ground instead of the heater winding CT.

I read in the same rob Robinette page that cathode biased amps can run center lug to pin 8 of a power tube. Are these reissues not cathode biased.

[Helmholtz]

I read in the same rob Robinette page that cathode biased amps can run center lug to pin 8 of a power tube. Are these reissues not cathode biased.

JTM45s are not cathode biased, they use fixed bias with cathodes grounded.

[The Dude]

Indeed. And, the schematic is in post #7.

[ca7922303]

JTM45s are not cathode biased, they use fixed bias with cathodes grounded.

Thanks

[ca7922303]

...

So to clarify, can I run center lug to filter cap ground and run 1 lug to any preamp tube(V1-V4) pin 4/5 and the other lug pin 9 and cross the wires tightly enroute to pins? Thanks.

[Helmholtz]

So to clarify, can I run center lug to filter cap ground and run 1 lug to any preamp tube(V1-V4) pin 4/5 and the other lug pin 9 and cross the wires tightly enroute to pins? Thanks.

Look at your picture from post 85.
Left side of PT has 6 terminal lugs. Let's number them starting from lug 5 (top) to lug 10 (bottom).
The first 3 (large) lugs (5,6,7) belong to the heater winding.
Connect one end of your humdinger pot to lug 5 and the other to lug 7.
Remove both black wires from lug 6 (no wire should connect here, being the heater CT).
Connect the center lug (wiper) of the humdinger as well as the wire from lug 9 (HT CT) to the grounding point at the filter cap above.

[ca7922303]

Look at your picture from post 85.
Left side of PT has 6 terminal lugs. Let's number them starting from lug 5 (top) to lug 10 (bottom).
The first 3 (large) lugs (5,6,7) belong to the heater winding.
Connect one end of your humdinger pot to lug 5 and the other to lug 7.
Remove both black wires from lug 6 (no wire should connect here, being the heater CT).
Connect the center lug (wiper) of the humdinger as well as the wire from lug 9 (HT CT) to the grounding point at the filter cap above.

Thanks, appreciate all the help.