funny voltages on my rocket

[beasleybodyshop]

Are you power tubes wired like this.

yeah it is. none of the pins are touching other pins

[Reeltarded]

Yeah, and auto-ranging meter can be a bummer.

All outputs redplate?

[beasleybodyshop]

hmm. im using a shielded cable from the master volume to the power tubes. one side of the shield is grounded. maybe the shield is shorting against the double conductor? Going to look at the tomorrow morning.

[beasleybodyshop]

Yeah, and auto-ranging meter can be a bummer.

All outputs redplate?

yes all power tubes replate equally.

[Reeltarded]

Single conductor from the master. That shield is not helping anything and it probably is your low signal problem.

OOOHHHHH ppimv. NIX IT kill that delete it. make the amp work then install it.

I was thinking if a pair was going hot it was just an output coupler..

[beasleybodyshop]

Single conductor from the master. That shield is not helping anything and it probably is your low signal problem.

OOOHHHHH ppimv. NIX IT kill that delete it. make the amp work then install it.

I was thinking if a pair was going hot it was just an output coupler..

I disconnected the two preamp wires goin to pins 2 on the power tubes, still red plates. This has to be in the power section exclusively.

[Reeltarded]

Its the PPIMV is what it is. I'd wink but you might think I'm kidding.

One little mistake, a bad part, a tiny failure and nothing but a mess. I have seen guys chase that tail for weeks and eat a crate full of tubes doing it. I have an amp with it in there because I am lazy.

[beasleybodyshop]

So, disconnecting the two wires from the master altogether would still cause it to red plate?

[didit]

Single conductor from the master. That shield is not helping anything and it probably is your low signal problem.

OOOHHHHH ppimv. NIX IT kill that delete it. make the amp work then install it.

I was thinking if a pair was going hot it was just an output coupler..

I disconnected the two preamp wires goin to pins 2 on the power tubes, still red plates. This has to be in the power section exclusively.

Double check your cathode resistor and bypass cap. Measure resistance to ground and perhaps cap polarity.

[beasleybodyshop]

Hope everyone had a happy new years! After a quick jaunt down to San Antone, I cleared my mind and started fresh.

Noticed a big problem this time around: Cathode voltage on the power tubes is 28vDC - much higher than the 8v i see in the voltage chart. I touched up all the solder joints on the cathode wires to ground, going to clip the ground wire at the chassis and check for resistance/continuity and see if I have a short somewhere.

UPDATE: So i clipped the cathode ground at where it attaches to chassis - Not reading any resistance at any of the cathode pins - after reconnecting, I get approx 50 ohms resistance between each cathode to ground - this checks out to be ok. Ive clipped out the cathode bypass cap and measured resistance - 24 Meg ohms. Does this mean its bad? I was under the impression caps should never read resistance.

[didit]

The 24M ohm reading off the cap is OK. Probably just a meter issue.

Assuming the power tube are still simply disconnected? Floating grids are bad. They should be tied to ground, probably preferably just through that pair of 220K resistors that are missing in your photos.

Best ... Ian

[beasleybodyshop]

The 24M ohm reading off the cap is OK. Probably just a meter issue.

Assuming the power tube are still simply disconnected? Floating grids are bad. They should be tied to ground, probably preferably just through that pair of 220K resistors that are missing in your photos.

Best ... Ian

Ok. reinstalled the 220K resistors and hooked it all back up pre PPIMV.

Voltages at cathodes show 10v now, but I watch and it begins to creep up very slowly. Tubes still try to redplate, but it takes much longer to do so.

Eh? What am I missing. I guess I will go over all my grounds again...

[cbass]

All the tubes are redplating?do you get any voltage at the grid when the tubes start to runaway?
You've bypassed the MV for now?

[beasleybodyshop]

All the tubes are redplating?do you get any voltage at the grid when the tubes start to runaway?
You've bypassed the MV for now?

yeah all of them are redplating. I am getting about 4vDC at the grids, and it starts to climb as well

yes ive completely removed the MV for now. I have the 2 220K resistors going to ground/grids in now, like the stock schematic shows.

[Reeltarded]

Creeping up..

Swap PI tube? Remove PI tube?

WAG.. Lift the inout to the PI at the PI, don't leave a wire hanging off it. (antenna) and that still wants to go China Syndrome? Just looking for runaway signal out of audible range, that's all. I am out of big ideas.