MB Dual Rect Tremoverb

[lowell]

The one I have here has a 120ohm 10w resistor from the Blue PT tap that goes to the anode of a diode to the board. I'm not sure where to thereafter. The schematic shows no such thing. The Blue tap also goes to the bias supply before the 120ohm resistor. I am retubing this thing and the resistor is smoking. Not a ton, but some. Getting 30VAC across it so its operating at 7.5watts. Unless that's RMS, in which case it's more. Maybe I just need to replace it or add a heat sink, but was curious what is drawing current from it. There is a schematic here..http://guiguijones.free.fr/Electroni...mesa.htm#tremo

[g1]

The drawing for part 1 of the switching matrix is missing. Some of the other models have the matrix running from something similar to what you have described.

[Jazz P Bass]

Here is the complete schematic.

And, yes, the blue 50Vac wire goes to the bias supply & the switching matrix.

boogie_tremoverb.zip

[g1]

7.5W does not seem unreasonable on a 10W resistor. If current was supposed to be significantly less they probably would have used a 5W.

[lowell]

I'm thinking it might be 30VAC rms. Not sure if rat shack meter is rms or not. Doesnt say. What would peak be? 30x2/.707? Resistor shouldn't be smoking at 7.5w

[g1]

30VRMS or 30VDC both work out to 7.5W. I'm not sure how there could be more voltage there than what you are measuring.
Maybe there is some residue on the resistor that is smoking?
Was there any reported fault with the amp, or just re-tube?

[lowell]

Just retube. Bias supply is fine, bias current is good too. Not that those affect the resistor anyways.

[lowell]

One of the low V supply caps had a cold solder joint, seems that the resistor stopped smoking after fixing that.