diagramz 4 dummiez

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diagramz 4 dummiez

Postby nyazzip » Mon Nov 23, 2009 10:41 pm

does anyone know where i might find some simple gain stage layouts/photos/diagrams (NOT just schematics)? i very slightly understand schematics but i could never lay out a circuitboard section based on a schematic alone...
i just want to find a simple 2 tube gainstage with a volume pot for that little PP el84 i have, no tone stack(yet)
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Postby jonnyeye » Thu Nov 26, 2009 10:15 am

What kind of layout are you looking for? Fender-style stripboard, tag strip, true point-to-point? If it's just a couple of gain stages I could sketch something up quickly.
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Postby nyazzip » Sun Nov 29, 2009 1:23 am

i think i might try this:

Image

with this old thing:

Image

and just pray the transformers are up to the task. the machine is tube rectified(5y3? i don't recall) so i will diode it like in the schematic, ease a bit of burden on the PT
first purchase will be some turrets and maybe the setting tools, if i can't use a woodworking awl to do the trick(wish i had a fresh turret to look at, damn why are these things so rare? guaranteed i wouldn't find any at radio shack or anywhere to experiment with before i spend $50 on a few turrets)
i did buy a pack of very small screws awhile back as turret stand-ins and i couldn't get anything to stick to them. and that was with a 75 watt iron....
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Postby azazello » Sun Nov 29, 2009 1:34 am

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Postby nyazzip » Sun Nov 29, 2009 2:08 am

i don't really understand the power section of that PA schematic, but it seems to run higher voltages in general which could be a problem for me. is it diode rectified? i can't quite discern some of it
the term "PA" scares me a bit too; i don't desire headroom with this project. anyway, how much "public addressing" is one going to achieve with 20 watts?
cheers
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Postby azazello » Sun Nov 29, 2009 5:37 am

This is diode rectif. schematic. You need power transf. with secondary coil whit 2 x 300 v AC. /Die from 230 or 300 v is the same! O:) /
There is and value of some control point, that is very IMPORTANT!!
/I have the same ampl. and I am glad to play/.
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Postby EWBrown » Sun Nov 29, 2009 2:25 pm

One potential pitfall with the open frame Hammond 216M6 is that it throws a strong 60 Hz magnetic field which WILL couple into any open frame OPT like the Hammond 125E. Even trying the "90 degree" separation between core exes will not be effective.

Elsewhere on this forum I wrote up the results of using the same power trannie, and a 125ESE, and the power trannie radiated a magnetic field which was picked up by the OPT at a distance of nearly two feet.

This magnetic field will do an "end run" around all the amplifier circuitry and create an essentially incurable 60Hz hum problem.

If you use a steel chassis, and botom plate, and can fit the OPT under the chassis, and as far from the power trannie as possible, it may reduce or even prevent the problem. The other (and probably easiest) solution is to use an "enclosed" OPT with steel bell ends.

/ed B
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Postby nyazzip » Sun Nov 29, 2009 9:43 pm

naw i'm not using no steenkeeng Hammond....its the original VOM trannie set(OPT is disconnected in photo). it has some codes stamped into it that read "12560-3" and below, "549824". i surrounded the whole deal with wine crate stock so i could flip it around a gazillion times an hour without a)getting electrocuted and b)damaging stuff: *addendum, based on the code i suppose it is a Midwest Coil and Transformer from 1958


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