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Post subject: Re: PT question
Posted: Sun May 04, 2014 6:14 pm
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Then the only question remains, what speaker configuration? A pair of tens, a twelve, or -- for the JR Ewing that lurks in all of us -- a big fat fifteen?

:wink:

Arjay

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Post subject: Re: PT question
Posted: Sun May 04, 2014 7:17 pm
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upnorth, Yup, your PT is very close in voltages to the 125P1B (early BF Princeton) and should be fine for a 6V6GT push-pull, cathode-biased amps based on either tweed Deluxe or AA964 Princeton circuits (minus the tap for fixed bias supply). Data is similar to the Hammond 290AX replacement PT.

May even have enough current off that PT to push another 12AX7 for a tremolo/vibrato circuit, similar to the Deluxe AA763. I think this can be done with a 5Y3GT rectified PSU. As the opto-bug tremolo doesn't use as must power as the two or three-tube harmonic oscillator circuits of the brownface era. Be interesting...

Good luck with your project!


http://www.hammondmfg.com/pdf/EDB290AX.pdf

http://bmamps.com/Schematics/fender/deluxe_aa763.pdf


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Post subject: Re: PT question
Posted: Sun May 04, 2014 7:59 pm
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BMW2002Ti wrote:
May even have enough current off that PT to push another 12AX7 for a tremolo/vibrato circuit, similar to the Deluxe AA763. I think this can be done with a 5Y3GT rectified PSU. As the opto-bug tremolo doesn't use as must power as the two or three-tube harmonic oscillator circuits of the brownface era. Be interesting...


I was thinking that myself if there's sufficient space on the chassis to mount another socket. A simple oscillator circuit (a la the original Tremolux) wouldn't even require a vibro-roach.

Arjay

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Post subject: Re: PT question
Posted: Mon Aug 04, 2014 6:58 pm
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The mystery PT has a partner. We'll see how this works out.

Image

Image

Image


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Post subject: Re: PT question
Posted: Mon Aug 04, 2014 7:20 pm
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Is there a choke lurking in your future?

Arjay

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Post subject: Re: PT question
Posted: Mon Aug 04, 2014 8:32 pm
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Are you speaking of the one from my wife if I keep buying stuff ? :lol:

I hadn't considered that, would help with hum also.

My rebuilt P12Q is on it's way back from Dusty. It was done within 2 days.


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Post subject: Re: PT question
Posted: Mon Aug 04, 2014 8:47 pm
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Dusty has an excellent turn-around time for most jobs.

Yeah, I was thinking a choke would be a great way to ensure ripple-free DC for your B+ supply.

Arjay

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Post subject: Re: PT question
Posted: Tue Aug 05, 2014 1:55 am
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I agree with the choke. Put a 4 or 5H one, between the tap to the OPT and output tubes --- and the gain stage tubes. Replacing the 1k-ohm, 2-watt resistor's position in the 6G3 PSU rail (point X). It will make a difference in background noise, generated in the high-gain pre-amp stages. IMHO.


http://bmamps.com/Schematics/fender/del ... _schem.pdf

http://angela.com/hammondchoke194a.aspx


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Post subject: Re: PT question
Posted: Tue Aug 05, 2014 10:13 am
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Well doesn't look like this PT is going to work. I can only get 260v for the plate voltage. (JJ 5Y3} Time to order, maybe a Classic Tone 40-18021 or a Hammond 290AX.


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Post subject: Re: PT question
Posted: Tue Aug 05, 2014 10:27 am
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Bummer!

I don't think you'd even get a pulse from 6V6's with only 260 volts.

:(

Arjay

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Post subject: Re: PT question
Posted: Tue Aug 05, 2014 11:32 am
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Just ordered the Hammond 290AX from Mouser. Don't know what I could use this PT for yet, maybe it's bad.


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Post subject: Re: PT question
Posted: Tue Aug 05, 2014 12:56 pm
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That's an assumed risk with "mystery parts".

Arjay

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Post subject: Re: PT question
Posted: Tue Aug 05, 2014 4:53 pm
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upnorth wrote:
Don't know what I could use this PT for yet, maybe it's bad.


If you pull all tubes, what is the B+ reading?


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Post subject: Re: PT question
Posted: Tue Aug 05, 2014 9:37 pm
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I forgot to jot that down but I believe it was 314v. I already pulled it.


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Post subject: Re: PT question
Posted: Tue Aug 05, 2014 11:14 pm
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upnorth,

Maybe can use the PT for single-ended 6V6GT or EL84 amp. Like a simple early tweed amp era Champ. One that uses one 12AX7 and one output tube. The B+ maybe good enough for these simple circuit.


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