Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Willabe on July 24, 2011, 01:37:59 pm
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Will I have a problem running the OT primary wires here?
Also, do you guys think the trem foot switch jack and speaker jacks are good here? Do I need to move them further away from the bias pots and/or each other?
I'm ready to finish drilling out the chassis, just not sure where the best place is to run these.
Like #2 drawing.
Thanks, Brad
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I do this stuff all the time but, sorry, I don't understand your drawing.
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On the drawing where it says OT Prim. thru chassis not eyelet board, I was thinking of moving that chassis hole to where it says New( with the arrow)then with that move the CC eyelet up as the arrows show, flip flop the 2 M's. I'm worried about the OT wires messing with the coupling caps and the 220K grid return R's.
Like this?
Thanks, Brad
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I am looking down at the top of the chassis? Still a bit lost.
Get all the parts and lay them out on the actual chassis and take a picture.
Maybe I'll get it then.
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No inside the chassis, looking at the guts/eyelet board.
Looking for good/best place to drill the hole to bring inside the chassis the OT prim. wires, which will end up under the eyelet board and go to pin 3, plates of OP tubes.
A picture of the outside of the chassis wont help, it's the inside that I'm worried about. The input and output of the OP tubes are out of phase? If I run the OT prim. wires too close to the input CC and 220k grid returns is that going to be a problem?
What is safe as far as placement of these wires and components?
Also the speaker jacks and trem Ft. Sw. jack?
Thanks, Brad
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Hiya Brad
Why not follow the same basic layout as the 5G9 http://ampedia.redbeartrading.com/data/schem_layout/tremolux_5g9_layout.gif (http://ampedia.redbeartrading.com/data/schem_layout/tremolux_5g9_layout.gif) (albeit that you'll have your caps inside and a few other bits added like bias TPs and pots etc)? The OT primary can be more or less 'next to' the output tubes and the plate wires can simply come through a hole and be right by the output tube sockets.
The trem footswitch jack can be 'next to' the trem tube socket
Pete
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Why not follow the same basic layout as the 5G9
I can't do that. I added a bunch of things ( VVR/ Power Scaling, Sag, ect.) preamp/PI/trem tube on other side of chassis by pots.
I could use shielded cable for the trem Ft. Sw, or move it away from the OP tubes to the left.
Every thing else will work fine, (I think :think1:) just these last 2 or 3 things.
Thanks, Brad
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Here's a drawing showing the OT placement (on the out side of the chassis) while looking at the gut/in side of the chassis.
I should have done/drawn it this way first, sorry.
Thanks, Brad
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It's really difficult to tell where the PCB is. Most amps have the OT outside and use a grommet to feed the OT prim and secondaries through . some feed the primaries throuhg one area and the secondaries through another area. Are you just trying to avoid running the leads under the PCB? As long as the OT leads are near the output section of the chassis they are fine . This drawing is just a flat one dimensional , also there is a third lead of the OT if this is a push/pull amp that needs to go the the B+ at the filter caps. I usually run then all through the same hole in the chassis unless the OT leads are going to reach a bit then I run the primaries as close to the OT section as possible and the secondaries as close to the output /speaker jacks so as to keep running leads across inside the chassis and to keep them outside the chassis .
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Are the OT primary wires coming through the chassis right at where the wires runs from the phase inverter coupling caps feed the output tube grids? If so, it's generally a bad idea to put a large output signal (plate wires) right next to a low-level input circuit (grid wires, bias circuit).
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You can run the wires on the outside of the chassis and run them through a hole where you want them to be terminated.
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You can run the wires on the outside of the chassis and run them through a hole where you want them to be terminated.
Are the OT primary wires coming through the chassis right at where the wires runs from the phase inverter coupling caps feed the output tube grids? If so, it's generally a bad idea to put a large output signal (plate wires) right next to a low-level input circuit (grid wires, bias circuit).
Yes.
That's what I'm trying to figure out, where should I bring them thru the chassis? Twisted pair (should be 3, push/pull/CT) from OT sec. to the plates, pin 3, of the OP tubes. I think I might have to bring the OT CT wire into the chassis thru a different hole?
Here's another drawing, moved the OT wires away from the CC and grid return R's.
BTW, eyelet board will sit 3/8'' off of chassis.
Thanks, Brad :w2:
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Is this your plan?
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Is this your plan?
Yes.
It started like this drawing below. But I've moved the 2 wires location and the CC and 220k grid returns after hearing from HBP, tubeswell and LC.
I can still move these around a little if I would be better off.
Brad :w2:
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It's easier for others to see your plan if you DRAW the proposed plate leads. Rather than connect-the-dots with some pin-3s, a grommet, and an OT which isn't even shown on your latest CAD.
My first question is: who will be touching the outside of the chassis? And how wet and/or stoned will you be? True, the 400 deg F tubes deter poking, but even a quick brush of 400V is dangerous.
If careless contact is difficult AND insulation is thick and robust, there's no great objection to coming through the chassis ASAP.
Stay away from the preamp tubes.
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PRR,
Thanks for the reply? :dontknow:
And how wet and/or stoned will you be?
:huh:
Brad :w2: