Bogen PA amp to 5F6A Bassman conversion

[Geezer]

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 jennifers3boys
Junior tube assistant
Posts: 1
(6/13/05 6:08 pm)

ezSupporter
 Bogen PA amp to 5F6A Bassman conversion
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 I'm converting an old Bogen PA amp to a 5F6A Bassman head. The way the chassis is set up, there is much more room for the fiber board, caps, resistors, wiring, etc. in the section where the tubes and transformers reside. The old wiring was on the opposite side of the chassis. Is there a problem electronically with putting the wiring on the same side as tubes and transformers? There are plenty of holes in the chassis to route wires to the tube sockets. thanks for any assistance...
 
triode3
Junior tube assistant
Posts: 50
(6/13/05 9:08 pm)
 Re: bogen, wires outside da house
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Hrm, now that is a good question.

Although I can not give any hard examples, or back up what I am going to say without breaking out my e-mag book,
I would say the following:

I think it is bad practice due to these reasons: the wires themselves would get hot, you have a much greater chance of picking up interference and noise from the tube to the wire or vice-versa, you
also have a better chance of picking up noise from outside the unit
if the wires are not in a grounded "cage" (ala, the steel chassis), also,
reverse that in that you problably have a better chance of injecting
noise into other units sitting next to it due to the above reason.

[Geezer]

I would also point out that the difficulty in wiring it up and troubleshooting get multiplied... "now this is which yellow wire?"...
I have worked on old (60's) tube stereos that did that, but the
wires were still in the chassis and they did not run on the same side
as the tubes, just under boards or panels. Ugh what a nightmare.

Hope that helps some in your descision making. I would say if you
_had_ to do it perhaps, but even then I would choose which
wire to run "tube side" very carefully, and I would make it a very
good wire (high heat high voltage teflon wire from Belden comes
to mind... and I would use GROMMETS!)
 
ampcabinets
Hey get your own solder
Posts: 221
(6/13/05 11:53 pm)

  Re: bogen, wires outside da house
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 seems to me it would cause a lot of hum and or other noise problems if it were directly under the tubes and especially the output transformer. I would build the board and mount it towards the area away from the hardware. Be sure to press the wire(s) down to the chassis, when running the tube wires and stuff to keep the residual noise down. If you lengthen the wires from the trannies to the board, be sure to use shrink tubing or better yet, a double layer of shrink tubing for the HV wires. Sometimes I even coat them with epoxy before adding the shrink tubing, but while the glue is still wet. (silicone works, too).
If you have brittle wires, I would shrink tube them up, just for safety's sake, leaving some open on the ends to see the color codes.
Rember, safety first................tone next, looks last, (but important to some).

There, you have my $.02 worth.
rob

[Geezer]

edited to add:
The original bassman board leaves a lot of room for "scrunching" the parts together. Since it has 2 channels, you can even use 2 boards. You might want to do cardboard mockups of your board(s), including drawing in the parts, before cutting them or having them made and get it right before spending your money. The filter caps can be added on yet, another small board under the chassis.



Edited by: ampcabinets at: 6/13/05 11:58 pm
 
tubenit
Hey get your own solder
Posts: 289
(6/14/05 6:55 am)
 Bogen chassis wiring
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 They're right, it would probably be noisey and possibly not safe using your considered method.

I have done 3 Bogen conversions using a messy point to point wiring. All so quiet at idle, I was first concerned that they weren't working til I hit a guitar lick. And they all sound great to me. I followed Doug's grounding scheme in the Library of Information on his website.

Last one I did, I used terminal strips in a paralleled fashion to make it a little neater and a little more serviceable. Yeah, it still is not neat work compared to a board. However, the amp sounds superb and it's just an obsessively fun hobby and I don't need to sell what I build. (I definitely don't get any extra points for neatness.)

If you look at the current post "homebrew guitars/amps" and go to the posted pictures and do the slide show ..... you can see the insides of 3 different Bogen chassis's with one using the paralleled terminal strips.
 

[Geezer]

j allen shaw
I only work on Fender's
Posts: 711
(6/14/05 8:05 am)

  Re: Bogen chassis wiring
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 On the Bogens, I have to vote for the PTP wiring, too.

I converted a K10 (2x 6AQ5) into an 18watt Marshall circuit (Lite II w/ paralleled triodes V1) and just wired everything in the same style as the original....one conponent soldered directly to the next.
Super quiet, and a kickin' little amp, too! (one of my favorites!)
I didn't dress mine up (like tubenit did)...just left it "industrial" looking (mounted a handle on the top). That way people are really suprised when they hear the cool tones coming from it!

Of course, the 18Watt is way simpler a circuit than the 5F6A....it could get confusing (?) when soldering everything in.

Jeff