'76 JMP50 resistor wattage

[Jaymz77]

Hi all, long time no post!


Im just wondering if someone can tell me what the stock resistor wattage is in these older amps, specifically the 27k/ 220k resistor before the diode in the bias supply circuit?
I just scored a good deal on a '76 JMP50 and when i opened it up i could see some repairs had been done. The 10u caps in the bias supply circuit had been replaced at some time as well as the diode and the resistor i mentioned above. The person who did it did a very sloppy job and i want to replace the crappy little resistor they used with a period correct one.


Im thinking 1/2 watt? Correct?


In other news, the PT has been replaced (i knew that going in), the main filter caps had been replaced (not uncommon), the presence pot has been replaced and some other sloppy wiring has been done because whoever did it was too lazy to lift the board to do the job properly.
The good news is that the OT is original!


thanks in advance.


Cheers

[sluckey]

Resistors of that time period will typically be 1/2 watt unless otherwise specified on the schematic. That 27K should probably be 15K according to the schematics I found.

[BlackCrowe604]

Hi all, long time no post!


Im just wondering if someone can tell me what the stock resistor wattage is in these older amps, specifically the 27k/ 220k resistor before the diode in the bias supply circuit?
I just scored a good deal on a '76 JMP50 and when i opened it up i could see some repairs had been done. The 10u caps in the bias supply circuit had been replaced at some time as well as the diode and the resistor i mentioned above. The person who did it did a very sloppy job and i want to replace the crappy little resistor they used with a period correct one.


Im thinking 1/2 watt? Correct?


In other news, the PT has been replaced (i knew that going in), the main filter caps had been replaced (not uncommon), the presence pot has been replaced and some other sloppy wiring has been done because whoever did it was too lazy to lift the board to do the job properly.
The good news is that the OT is original!


thanks in advance.


Cheers

Yes all resistors are 1/2 watt unless specified otherwise.

As for "period correct" Marshall had some dark brown/burgundy colored resistors. I've never actually been able to find identical ones. I use 1/2w 1% metal film. If anyone knows where to find the style of the original Marshalls, please share?! (I'm a sucker for aesthetics I guess).


27k in series where the WHT lead from PT is connected to the board & 220k grid leaks for EL34s.

15k & 150k are on a lot of schematics, but this was typically the config for N. American Marshalls shipped with 6550s.

There are some 2203&2204 schems with the 6550 values in parenthesis for N. America.