Problems with 5F11 build, no sound and high b+

[ron vogel]

Ok,
Here's the deal. I am getting no sound at all, heaters work, b+ is 465v to 500 (depending on what outlet I'm using (my kitchen outlet is 138VAC!)

I went over the wiring several times, everything is hooked up right, went as far as pulling resistors and measuring them.

Using an Edcor 300-0-300 PT (w/o bias tap / using 6G3 method) bias voltage -38v

Using Mag Comp OT 40-18090 8K winding with 4/8/16 ohm taps...using only 8ohm.

I'm thinking the amp may be in some sort of runaway osc...but the fact b+ is so high leads me to believe the tubes aren't pulling down the voltage.

The only other thing that is suspect is the twisted pair heaters I used. However the heaters work.


Any ideas what to look at here? I'm pulling my hair out, everything seems to have a good connection, and I know the hook ups are perfect.

[ron vogel]

Also,
I just had a long talk with an engineer at Magnetic components (they are across the street from where I work). He pulled out the the 5v4 operational sheet and we tried to come up with a hypothetical B+ on this set-up...Should be low 400's.

He thinks the output tubes are not drawing power, and gave me a few things to measure.

Any other help would be appreciated.

[g1]

Do the power tube cathodes have a good ground connection? What are the grid and screen voltages at the power tube sockets?

[ron vogel]

The original schematic calls for pins 1, 2, and 8 to be connected together and go to ground. Using the "twisted pairs" for the heaters, 2 and 7 are for the heaters, and 1 and 8 should go together with no ground. Should I be grounding 1 & 8? Inquiring minds want to know!

[g1]

Pin 8 must be grounded or the power tubes will not run. Pin1 is unused so it can be left open. (it is often used as a tie point for the grid stopper resistors in Fender layouts)

[ron vogel]

Thank you...at work I made the ground straps for it...will try when I get home. Figured it was something dumb.

[ron vogel]

Tried it...works.

6V6's are almost to melt down though. Kinda figured that would happen. B+ is still in the 480 range.

Going to have to find a 5y3 for it, and start the biasing process. Glad I put the crappy tubes in it for start-up...but I have to say, for even in it's current state of tune...doesn't sound half-bad!

[ron vogel]

Ok...I am officiall an idiot. My voltmeter needed a new battery...lol

Ok...new problem. I think the PT is too small. I have a 300-0-300 120ma Edcor. With the 5v4 I am getting 340...perfect. However without a bias tap I don't think there is enough voltage to get the.primary. positio re"6g3" style.I can only get down to about -25v..and it is pulling so much current it is smoking the 10k resistor

[ron vogel]

I am on my phone...bear with me! I imagine it might help to raise the 220k value and lower the 10 k resister..chage the 56k in the filter to 22k? BTW...popped the 25/50 in the filter...made the wife jump...lol

[ron vogel]

Ehh...I'm going to start a new thread...I was a little baked last night after I got done...after sleeping on it I have some ideas.