Marshall 1962 Bluesbreaker (JTM 45) Reissue Hum

[ca7922303]

Should work fine, but a 100R/1W pot would be completely sufficient.

Any ideas on the treble, bass, midrange not functioning? Thanks.

[Helmholtz]

Any ideas on the treble, bass, midrange not functioning? Thanks.

Again, does the tremolo work?
And what else does work?

[ca7922303]

Again, does the tremolo work?
And what else does work?

Tremelo and presence work.

[g1]

Any ideas on the treble, bass, midrange not functioning? Thanks.

Check that the mid pot is grounded at one end.

[ca7922303]

Check that the mid pot is grounded at one end.

Mid pot is 3rd from right. Looks grounded to me.

[ca7922303]

Mid pot is 3rd from right. Looks grounded to me.

But DMM shows it is not grounded at one end.

[ca7922303]

But DMM shows it is not grounded at one end.

Just grounded one end of mid pot, now all control pots are grounded except speed.

[ca7922303]

Just grounded one end of mid pot, now all control pots are grounded except speed.

Hum is now down enough to record I believe. Should I ground the speed pot?

[g1]

Hum is now down enough to record I believe. Should I ground the speed pot?

Speed pot does not go to ground, it goes to internal trim pot and that is grounded. Does speed control work? All tone controls working now?

[ca7922303]

Speed pot does not go to ground, it goes to internal trim pot and that is grounded. Does speed control work? All tone controls working now?

Speed control works, all tone controls working. Hum goes down after a few seconds. Will install humdinger when it delivers. Changed rectifier tube. Output seems stronger, less hum. Really appreciate the great help as always. Thanks to all.

[g1]

So I guess the mid pot just had a bad connection that needed to be re-soldered? It was the pot with the white wire and it already had one lug grounded to it's case. Then there was a black wire running from that whole ground buss (next to presence pot) back to the circuit board. Maybe that had the bad connection?

Also, the cap we had been looking for was at the intensity pot. It is half covered by the heatshrink. It's the very small bead type capacitor.

[ca7922303]

So I guess the mid pot just had a bad connection that needed to be re-soldered? It was the pot with the white wire and it already had one lug grounded to it's case. Then there was a black wire running from that whole ground buss (next to presence pot) back to the circuit board. Maybe that had the bad connection?

Also, the cap we had been looking for was at the intensity pot. It is half covered by the heatshrink. It's the very small bead type capacitor.

I soldered a wire from one end of mid pot to the common ground wire that was run across the back of all the pots.

[ca7922303]

So I guess the mid pot just had a bad connection that needed to be re-soldered? It was the pot with the white wire and it already had one lug grounded to it's case. Then there was a black wire running from that whole ground buss (next to presence pot) back to the circuit board. Maybe that had the bad connection?

Also, the cap we had been looking for was at the intensity pot. It is half covered by the heatshrink. It's the very small bead type capacitor.

So when I get this humdinger pot, do I wire the middle lug to pin 8 of one of the power tubes and then the other two lugs would go to pins 4/5 & 9 on any 12ax7?

[Helmholtz]

So when I get this humdinger pot, do I wire the middle lug to pin 8 of one of the power tubes and then the other two lugs would go to pins 4/5 & 9 on any 12ax7?

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

[The Dude]

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