Marshall 100 watt 1x12 model 2150....no heaters?

[acorkos]

This is the 1x12 100 watt marshall model 2150, celestion powercell speaker....it looks to be pretty much a model 1959 w/6550s and a post-PI master volume. There is a mains fuse on the back panel, and a fuse PCB w/9 additional fuses for filaments x 4, CT, HT x 2, bias and mains. All the fuses meter continuous.

I measure ~3.2VAC on all heater pins of all tube sockets. But none of the tubes are lighting up or feeling warm. Power tube plates and screens are measuring ~480VDC, and there's about -53VDC on pin 5 of each power tube...all normal.

These are the high voltages measured on the preamp tubes and phase inverter....
V3(PI) 461VDC pins 1 + 6
V2 pin1 456 pin6 451
V1 pin1 451 pin6 447

The 10k dropping resistors are all w/in spec, as are the plate resistors on V1-3

I am missing something here....maybe one or more of the cap cans are bad? thanks for your help!

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2150 Power amp schematic: http://drtube.com/schematics/marshall/78614-3.gif
2150 Preamp schematic: http://drtube.com/schematics/marshall/78614-2.gif

[Jazz P Bass]

When measuring the Vac on the heater pins, it is best to go directly across the heaters.
12AX7, pins 4/5 & 9.
EL34, pins 2 & 7.
I notice a lack of cathode voltage information.
This info will tell you if the tubes are conducting.
Plate voltage alone is lacking.

[acorkos]

ok....a couple of the filament fuses are blown.

i didn't mention in the original post that all 4 filament fuse holders were bypassed w/soldered wire leads. i removed the wire and installed 5A fuses, 2 of which (one side) have now blown. The box these fuses came in was labeled as T5A, but the fuses themselves are marked as only '5A'. I'm suspicious.

prior to this latest fuse-blowing incident, all new tubes were installed.

[Jazz P Bass]

The fuse chart shows parallel 5 a fuses. F7 & 8/ F9 & 10.
There is not an indication of T (slo-blo)
I would try it again with all of the tubes removed.
Measure the secondary resistances.
In fact check the wiring of the whole heater circuit.
Maybe someone tried to modify it.
The schematic shows two secondaries going to all of the heaters in parallel. With the center tap grounded.