I broke my DRRI....help red plating

[Greatmush]

While biasing I think I might have done something wrong with the multimeter.

The consequence is that now I have one 6V6GT red plating. I measured the amp on the tube and it is around 88 mA. If I pull out that tube, and measure the other tube bias, I get the right 20mA.

Can someone help me. I actualy live in a northern region of Québec Province. I don't have access to a tech.

I can make my way with all this with somekind of supervision.

Thanks

Mush

[Greatmush]

I forgot to had the it is doing that with an other tube also.


Mush

[R.G.]

I'm going to take you at your word that you can do this safely and skip my normal warnings about the possibility of dying while doing this.

Take both tubes out. Measure the B+ and the bias voltage on the grid pins of the two empty sockets, as well as screen voltages - B+ and screen voltages are just to be sure about the power supply.

You should be able to vary the negative bias voltage on the grid pins of the two output tube sockets by whatever means you have installed to vary bias. If the bias voltage isn't (a) negative with respect to ground and (b) adjustable to a range of up to -40V or more, there is a problem with the bias supply getting to the grid. If only one tube has the problem, suspect that tube's socket wiring back to the bias supply. If both grid pins have the same problem, suspect the bias supply itself.

[g1]

Also, a leaky coupling cap from the phase splitter to the problem socket could cause the high bias current.

[Greatmush]

RG, I'm at work now but I will check that tonight.

I'll post back tomorrow.

Thanks

[Greatmush]

I don't know what happened but I took R.G. measurements and put it all together yesterday after work, changed tubes and everything is OK. The amp sounds fine !

The red plating was occuring while taking bias reading, maybe it was a bad connection with the probe (the dangerous eurotube one ).

Thanks fore your help everyone.

Mush

[g1]

If the power tube sockets are directly mounted to the circuit board you should resolder them. A bad solder connection could cause the problem you were having if the sockets are board mounted.

[Greatmush]

No, they are not board monted.

Thanks

Mush