funny voltages on my rocket

[Colossal]

Picked this up today from an old ham radio guy ive recently made friends with. "Here" he said "I have ten or twenty of these and they arent doing me any good sitting in a box" !

Wish I a buddy like that! Don't blow that tube up!

[RJ Guitars]

Picked this up today from an old ham radio guy ive recently made friends with. "Here" he said "I have ten or twenty of these and they arent doing me any good sitting in a box" !

Hmmm... does your friend need any other friends?

[Reeltarded]

I replied first. DIBS

[beasleybodyshop]

Ok, some more updates:

(Preface - mains voltage is around 123vAC)

with rectifier installed, Recto heaters measure 4.9V with power ON, standby ON. When the standby is flipped off, recto heater taps measure 7-8V. I can see the plates on it start to slowly glow red. What gives?

My first thought was that maybe the dual 50uF cap can might be a bit too much for the rectifier. But I know Mark Fowler has had luck with using them before.

Thoughts? I'm stumped. For safety sake, i went out and scored a cheapie recto tube until this ordeal is dealt with.

Grr. So wanted to fire this bad boy up smoothly!

Attached are some more photos. Any obvious clues? I touched up all solder joints.

[beasleybodyshop]

I measured resistance from my grounds to chassis:
Both PT center taps to ground - .5ohms
first filter cap from rectifier - .5ohms
second cap can - .5 ohms


Measured resistance from OT CT to OT primaries : 95 and 110 ohms respectively.

I suspected some kind of short in the OT - because the recto heater voltages went up only after I turned off the standby switch.

What the eff??

[M Fowler]

Which transformers are you using? I wondering about wiring colors.

[beasleybodyshop]

I'm using Edcors from RJ.

[M Fowler]

Yeah but which models the wiring color seems funny to me.

OK that OT has dual secondary and your using 4k3 brown/white and blue/white.

Red/black is HT CT and White/brown is filament CT.

So have you put in all tubes and fired the amp up yet?

[beasleybodyshop]

Em0720 and em0708

[didit]

I had similar thoughts to Martin but given what I find on Edcor's site - the colours are those typically for UL screen tap so the 5K2 on a multi-primary - plus your resistance measurements have parked it.

My suggestions are perhaps a short in the 40-20-20-20 multicap -- but usually that involves smoke etc -- or maybe that particular GZ34 is unable to handle the current peaks from the 80mF of capacitance.

I'd really suggest going back to square two point something with half-bridge of 1N4007s. Perhaps you want to have some small value power resistors in series - i.e, 20-30 ohms or so on at the transformer end of each string of diodes, which somewhat simulates the rectifier.

Disconnect everything after the second multicap and then check voltages with a dummy load per my suggestion yesterday. In other words prove in isolation that your basic power supply works. If that all works correctly then put in the tube rectifier and test again.

If that works then all I can suggest is carefully check the wiring of the power amp stage again.

Best ... Ian

[beasleybodyshop]

Thanks ian, I have swapped in a SS rectifier and the issue still happens.

I could double check voltage on both my cap cans but they seem to be alright. I checked continuity across them and they aren't open.

My thoughts are there may be something up with those cap cans. Might order another set for grins.

[RJ Guitars]

I'll attach the drawings for the transformers, you can find them on my web page also but I'll make it easy for us. You won't find these models on the EDCOR page because they are a custom wind they do for me. The color code may be the same as their other transformers but I wouldn't count on it.

Hope this will help...

[M Fowler]

I must be missing something here

the issue still happens

What still happens? Increased voltage? Red plating power tubes?

[beasleybodyshop]

I must be missing something here

the issue still happens

What still happens? Increased voltage? Red plating power tubes?

According to both of the wiring diagrams RJ posted, I have both trafos wired properly. Both PT CT are grounded to chassis, brown wires are heaters, both yellows are rectifier, red is B+ to pins 4/6.

I gathered some more info:

Rectifier voltages power on, standby on using SS rectifier:
2 - 352vCD, 4.8vAC
4 - 252vAC
6 - 252vAC
8 - 352vDC, 0vAC (every time i put my meter on it, it wont give me an AC reading)

Here are voltages with the standby OFF:

2 - 292vDC, 8vAC
4 - 239vAC
6 - 237vAC
8 - 288vDC, 8vAC

Weird huh? rectifier heater doesnt have a center tap. Here are my B+ voltages with power on/Standby OFF:

B+1 - 295vDC
B+2 - 260vDC
B+3 - 197vDC
B+4 - 173vDC
B+5 - 168.9vDC

thoughts? I'm stumped as to why i don't get AC readings on pin 8 of the rectifier (maybe its because there is so much DC on the pin as well?) and why the heater voltages double when the standby is off.

Whenever i plug a guitar in, I get super weak output, and it tries to redplate the power tubes. I quickly took DC voltages on the power tubes with standby off, and i am getting 262vDC on the plates and 245vDC on the screens.

[M Fowler]

Are you power tubes wired like this.