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Old 7th March 2003, 03:16 AM   #1
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Default I found more junk!

I took the day off today, and was driving around my neighborhood ( on trash pickup day ) and found that someone had thrown out an old Sears Silvertone organ. So, i gutted the thing right on the sidewalk to see what was powering it. Sure enough- intact tube amp with all the original silvertone tubes. So i hacked it out of this old organ and brought home my new project.

4 tubes; 2x 12ax7a's 1x 5y3-gt 1x 6aq5a
1 OT, 1 PT, no choke ...it's got one of those old school 2x 40mf caps in a single silver can..and a big resister between the two positive contacts.

only 1 volume pot, .5M

Anyways, my question :
Can i use the aforementioned parts and chassis to build the Angela SE 6L6 guitar amp project? I'm most concerned about the 6AQ5A tube...

here's the schematic .....lend me your suggestions
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Old 7th March 2003, 03:27 AM   #2
Morse is offline Morse  United States
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Hi Magnetmaz;

Great find! Ummm, by the way, next time you find something like that don't forget about the speaker - it could be a decent fullranger.....

Anyway, about the 6AQ5 - it's basically a 7 pin mini 6V6, originally designed for auto radios IIRC. Run it as a 6V6 with a Vp of 250VDC and it should work well for you - figure around 49mA bias in class A1 according to the RCA Receiving Tubes Manual. If you insist on triode strapping it you ought to get something on the order of 1.8watts flat out; in pentode I think you should be able to get a little over 6 watts. Do not exceed 275VDC on the plate!

I'm still in the parts gathering stage for my own 6AQ5/12AV7, so you'll probably beat me to it.....

All the best,
Morse
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Old 7th March 2003, 04:08 AM   #3
SHiFTY is offline SHiFTY  New Zealand
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Why not just use it with the original components? The golden tone of guitar amps comes from the carbon comp resistors, leaky caps and the old AlNiCo speakers.

All being madly overdriven, of course. With 2 12AX7 it should have heaps of gain for crunchy distortion.

You could sub a 6V6 for the 6AQ5 (with a socket change), they sound better and are nice tubes, especially at 350-400V. And as for the can filter cap, I still use a couple of these in a hi-fi amp, they still work just fine!

I built a 5W EL84 amp (similar to the Kalamazoo model 1) and it is freaky loud. Neighbour unfriendly, even!

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Old 7th March 2003, 04:54 AM   #4
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Should make a great base for the Princeton, it's got all the tubes, for sure.

IMHO, don't worry about the voltage. Most guitar amps routinely go WAY over, anyway.
Besides, a 6AQ5 is what, $2?

BTW, if it was powering an entire organ, the power transformer might be huge (to supply the rest of the thing).. if it is, you could hang a few more of those amps off the power supply (you'd need a heftier rectifier, of course ).
For *just* a 6V6 SE, the PT might be 50W at most - uh, about 3" tall, 2 1/2" wide, 1" 'stack' (core dimension), so maybe 2" including end bells. If it's a big huge thing, like 5" on the longest side, it's definetly good for a lot more.

Tim
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Old 7th March 2003, 10:16 AM   #5
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Remember also that the 6L6 can run on a higher HT voltage than the 6AQ5/6V6, so even if the mains tranny is capable of supplying the extra current for a 6L6, it won't give its full output from the HT voltage available...
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Old 7th March 2003, 05:29 PM   #6
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Default pic of it

In response to Sch3mat1c :

Yeah, i think this PT only pushed the 6AQ5A. It's pretty puny, and the OPT is punier. The picture may show a bunch of gray cables hanging out of the left hand side of the amp chassis, and some white and black weaved ones on the right.

I've figured all the white/back ones out.. ( one went to an on/off switch, another to a 6.3v pilot lamp on the console of the organ, and the third to the speaker ). The other grey cables i'm having some trouble with. There's a total of 4 of them...i'm assuming 2 of them go to each of the 2 manuals on the organ. Perhaps the other two go to the sound control unit ( think Drawbars, but cheaper)....anyways, i gotta figure out where to wire in a 1/4" input jack, and how these 12AX7's relate to eachother...i.e. are they chained together as two gain stages, or was one 12AX7 for one manual ( and thus it's own preamp circuit ) and the other for the other manual.

any thoughts?

-Maz
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Old 7th March 2003, 05:32 PM   #7
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Default i'm an idiot

forgot the pic
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Old 7th March 2003, 07:18 PM   #8
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Yeah, that's not good for much more than what's there. Have fun with your amp!

Tim
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Old 8th March 2003, 03:30 PM   #9
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Probably easiest just to start afresh, strip the the two 12AX7s stages down completely and just leave the 6AQ5 and the power supply wired up - even if you do track down the circuit details as they stand you'd probably want to change the values of components for your new amp anyway.

Alternatively, a pp circuit based around triode pentodes of the ECL82/86 variety using the sockets of the 12AX7s would give you more power than a single 6AQ5 but not demand as much HT current as a 6L6 from the supply, although to be safe you'd need to cut out the pilot light to ensure sufficient heater current for the tubes. A new output tranny would be needed though...
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Old 28th December 2007, 08:49 AM   #10
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dunno if a schematic will help you out or not but I have one!


I bet you anything the organ had a vibrato channel, and that goes to one of your grey wires ( should have a green wire and a red wire in it). Is saved the pots and everything for mine. one of those was for volume, so make sure you figure that one out. Mine was ready for guitar already, as the amp came out of a reed organ ( used two weird mic's to pick up the sound from the reeds.)

The one I have is slightly different, 6v6gt,5y3, 12ax7a, 12dw7, but the schem I have is for yours...


Oddly enough the OPT in mine is huge! its larger than the PT, and about the size of a modern hammond 125ESE!
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