New Rectifier Tubes Pulling massive current.

[Intergalactic Tourister]

Sounds to me something's off with (one of?) your 6L6s, not the rectifier

I've tried 2 different brand new pairs of JJ 6L6GC.

[Intergalactic Tourister]

Unless you have verified your original rectifier in another amp, you can't use it as a reference for normal current 'pull'.
330V plate sounds abnormally low for a Fender 6L6 amp to me.

I think you're right. I'm also thinking a previous owner may have added this bias pot and biased this amp WITH the (faulty?) Tung Sol. I'm going to go ahead and add the 30k or so to the bias pot so the new rect tubes are in range.

[Enzo]

Wait. Isolate the problem. I see with the old tube AND 6L6s, we get one thing, and with the new tube and no 6L6s we get another and with the new tube AND 6L6s we get yet a third, but what about the old tube and NO 6L6s?

I wanted to know if the hum was 60Hz or 120Hz, that will be tough without a scope or freq meter.

I agree, test the old tube in another amp.

[Intergalactic Tourister]

Wait. Isolate the problem. I see with the old tube AND 6L6s, we get one thing, and with the new tube and no 6L6s we get another and with the new tube AND 6L6s we get yet a third, but what about the old tube and NO 6L6s?

I wanted to know if the hum was 60Hz or 120Hz, that will be tough without a scope or freq meter.

I agree, test the old tube in another amp.

Thanks Enzo.
With Tung Sol 5u4GB and with NO 6L6s I get 530 B+. (Was kinda bouncing between 528v and 533v though)

Ok. I can test the Tung Sol in another amp sometime tonight.

[Enzo]

Your bouncing is 5v out of more than 500v, less than 1%. A 1 volt change in your 120v mains will make that difference.

So it is the load bringing the voltage way low. The rectifier can't hold up.

And with no 6L6s, you have either way about 500v B+, but what is your bias voltage on pin 5? And if adjustable, what range?

[J M Fahey]

Thinking aloud and in no articular order:

* rectifiers, be it tube or SS pull nothing, thatīs the job of the load fed from that supply.

* low current and huge voltage drop across rectifier makes me think itīs dead, period.

[Intergalactic Tourister]

Your bouncing is 5v out of more than 500v, less than 1%. A 1 volt change in your 120v mains will make that difference.

So it is the load bringing the voltage way low. The rectifier can't hold up.

And with no 6L6s, you have either way about 500v B+, but what is your bias voltage on pin 5? And if adjustable, what range?

Odd.

The old Tung Sol worked in another amp w/ power tubes @35ma. BUT, the new JJ5u4GB also worked w/ power tubes @40ma. They both worked in another amp. Not what I would have thought at all.

So why is it that the old Tung Sol causes 6L6s to pull about 50ma but the new JJ5u4GB causes 6L6s to pull 100ma+ when installed in the amp in question? (all 3 of my brand new rect tubes also caused 6L6s to pull 100ma+ in the amp in question.)

I guess I'll just keep thinking about it... double checking things until I figure this out.

[Intergalactic Tourister]

what is your bias voltage on pin 5? And if adjustable, what range?

-30v to -14v sweep.

[Intergalactic Tourister]

Can your meter measure Hz / Vac on the HT?

With no power tubes in place and the bias control set to 'as cool as possible', what are the Vdc on power tube socket terminal #s 3, 4 and 5?

With the old Tung Sol in and no power tubes in:
Pin 3 = 535v
pin 4 = 548v
pin 5 = -30v (variable to -14v)

[frus]

So why is it that the old Tung Sol pulls about 50ma but the new JJ5u4GB pulls 100ma+

The rectifier doesn't "pull" anything, the power tubes do. The rectifier "supplies" the current
And since you posted your voltages, everything is clear. The bias range for 6L6's should be more like -55 to -40 V
Check the bias circuit

[Intergalactic Tourister]

The rectifier doesn't "pull" anything, the power tubes do. The rectifier "supplies" the current
And since you posted your voltages, everything is clear. The bias range for 6L6's should be more like -55 to -40 V
Check the bias circuit

Sorry, I already had to edit a post on just this. I meant, when I look down at my plate current, why do the 6L6s pull said current- Not the rect tube. Sorry about that. I corrected it.

Yes my suspicion is the bias. I also suspect it was biased, or rebiased, with the old Tung Sol in it.

[Enzo]

If I had to come up with something, I'd say the old rectifier sags so far the voltage drops to the point the tubes can't draw much more. Your bias voltage is way low, I'd expect more like -50v. So when you put a good rectifier in there, the tubes naturally draw a ton because they are under biased.

[Intergalactic Tourister]

If I had to come up with something, I'd say the old rectifier sags so far the voltage drops to the point the tubes can't draw much more. Your bias voltage is way low, I'd expect more like -50v. So when you put a good rectifier in there, the tubes naturally draw a ton because they are under biased.

Yeah I can bring it up to -50v. But at -50v, with the Tung Sol, the power tubes will be super cold probably single digit plate current... and the new JJ5u4GB will be in range.

[nevetslab]

Your Bias range needs to be more like -40V to -55V for 6L6GC's. With good rectifier tube installed, with bias anywhere in the range you stated here (-30V to -14V), they WOULD be pulling that much plate current. You need to adjust the bias circuit to increase the negative voltage swing.

[J M Fahey]

Yeah I can bring it up to -50v. But at -50v, with the Tung Sol, the power tubes will be super cold probably single digit plate current... and the new JJ5u4GB will be in range.

So you can solve the problem, just donīt want to, all "justified" by some misguided conception.

the power tubes will be super cold probably single digit plate current

WHO says so?
6L6 with proper plate, screen and bias voltages will pass the current thatīs expected from them, period.

Trying to make them "work" with only -14 to -30V bias (absolutely ludicrous values) is like, say, trying to deform the head to fit a wrong sized hat.

So in a nutshell: use a good rectifier, set bias to Factory suggested value (they "should" know) , measure idle current, which should be about perfect, and slightly tweak to adjust to desired value ... which will be very close anyway.