Bassman '59 Reissue Distorted Sound

[TNTim]

I've got a 2000 era Bassman '59 reissue. New filter caps. High voltages look good.

It's got a horrible distorted "fuzz" sound and low output. If you turn off the power, as the voltage goes down, the natural sound of the amp comes alive and then fades out with the power dissipating. I have about 487VDC at the 6l6 plate. -50v coming into grid. It's happening in both bright and normal channel. I assume from that it's probably in the power stage. The output transformer is around 46 ohms on each side between center tap.

Any ideas?

[Roe]

any chance the output transformer has blown?

[pdf64]

Screen grid voltages are as important as control grid and anode.
A full voltage survey, and output valve idle anode or cathode current, would be helpful.

[Stevem]

Both output tubes can not be idling properly if you have that high of a plate voltage showing up.

As posted check to see if the 470 ohm screen resistor on either tubes pin 4 is open.

[pdf64]

HT in the 59 RI does seem to run awfully high, especially with the solid state rectifier module https://el34world.com/charts/Schematics ... manual.pdf

[TNTim]

Both output tubes can not be idling properly if you have that high of a plate voltage showing up.

As posted check to see if the 470 ohm screen resistor on either tubes pin 4 is open.

Yeah I agree. According to the schematic, at TP7 (Plate voltage for 6L6) it should be 257. It reads 487.

486V at grid. R32 and R33 are 470 ohms 1W. Both of those resistors read 470 and are attached at pin 4 of each 6l6. I read voltage and it acts like the resistors don't drop much voltage across them while in use. Right at 470V on grid.

[sluckey]

According to the schematic, at TP7 (Plate voltage for 6L6) it should be 257. It reads 487.

Voltages within an oval are AC signal voltages, NOT DC voltage. Your measured 487DCV is correct.

[Stevem]

Dam! That is how high the plate voltage is on that so called reissue model.

No wonder they don't sound much the the originals when they had more like 450 on the plates

[TNTim]

So I think the issue is in the second gain stage and cathode follower. I have almost no voltage on both cathodes and over 400V across the 100k resistor attached to the plate.

[Roe]

So I think the issue is in the second gain stage and cathode follower. I have almost no voltage on both cathodes and over 400V across the 100k resistor attached to the plate.

try a new tube in v2

[TNTim]

So I think the issue is in the second gain stage and cathode follower. I have almost no voltage on both cathodes and over 400V across the 100k resistor attached to the plate.

try a new tube in v2

I tried that with 2 different good tubes.

[martin manning]

So I think the issue is in the second gain stage and cathode follower. I have almost no voltage on both cathodes and over 400V across the 100k resistor attached to the plate.

Measure resistance to ground from the cathodes of that tube , pin 3 and pin 8, with power off. See if you get the resistances on the schematic.

[TNTim]

100k resistor at cathode follower (pin 8 ) was reading 100k but when I finally got in there and messed with it, it shows an open. I replaced that resistor and buttoned everything up. Works like a charm now. I guess with voltage applied, it was opening and when I removed it would still show correct resistance. Either way that was the issue.

I hate working on these printed circuit board fenders. Such a pain to get to the solder points.

Thanks for all the help.

[Roe]

great