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Vintage threads from the first ten years

Schematic for Bogen CHB100

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6/7/1998 6:55 PM
Jack	Schematic for Bogen CHB100 Does any have access to a schematic for an old tube type Bogen PA amp model CHB100. It sounded great for guitar but now has a couple problems that a Schematic would fix.

6/8/1998 7:25 AM
Steve M	Jack, I got really lucky and found this in an old repair book a while back. I could scan and email you a copy if you like. Regards, Seve

6/8/1998 6:35 PM
Marc	jack, I've got a GIF I can send if you'd like- it's from jack Darr's book. It'a fair copy though th voltage chart is hard to read. Let me know... Marc

6/9/1998 7:51 AM
Pat F	I can send you a hard copy made from Darr's book. Let me know. I recently picked up the same Bogen at a garage sale. BTW did you know that the remote 1 and remote 2 terminals on the back are live 275VDC? I disconnected mine.

6/9/1998 11:03 AM

Pat: The "remotes" are used to ground the plate supply for each input channel so that you can "kill" each channel remotely. While there is 275 volts, or so, on each remote the current is limited (nasty shock, not lethal hazard). Since the discussion is to craft a guitar amp, I'd disconnect them too (have already done so on my 60w Bogens, haven't really gotten around to the supposed hundred watt amp yet).

This does remind me, the output tranny on this amp seems to be really undersized for a 100w amp - I would be hesistant to really push it for a long period of time. The tranny is actually smaller than the one in the 60w (8417 outputs) design.

Have fun with it, lotsa room to play around in the chassis.

Graywater

6/9/1998 10:16 PM

Graywater - I too thought the OPT was a bit small for it's rated output. But, I had an old Bogen 75W PA with a pair of 7027s and it had an even smaller OPT. As for the remotes, I understand the logic there, but I don't think any manufacturer could get away with something like that today when we have folks suing McDonald for serving hot coffee, you know what I mean? I'm not sure what I'm going to do with it yet. I cleaned it up and slowly reformed the caps because the guy I got it from said it was sitting in hit attic for 10 years. Well, it works fine. I got it for a song at a garage sale and couldn't pass it up.

Pat

6/10/1998 5:49 AM

Dear Pat: Well, I haven't decided what to do with my CHB100 either - pickedit up for $5.00 at a flea market. At one time I was going to sacrifice the amplifier usage and turn the chassis into a "under dynamic load" tube tester - drill out the 7868 sockets and add octals wired for a variety of tubes - add an on-board AF oscillator, and meter test points etc., but the project languished and now I use a little two tube three stage single ended class A amp for the testor/matcher - can't torture the tube under test as much as I once fantasized but it works.

Currently I have two Bogen M60As (genuine NASA surplus) - 8417 output, low impedance/transformer coupled inputs, that I have converted to guitar amps. One is in a cabinet I built and my primary LOUD amp and the other I use as a test bed fro strange and wonderful reverb mod testing. Both of these amps have outrannies that are half again as big at the CHB100. Somehow, since the M60A has low z inputs and a heavier design, I tend to think that the CHB100 was more of an economy PA designed for small churchs and schools. But who know, I am probably crazy as usual. If you fire your's up to full 100w let me know how hot it gets since I've never used mine beyond an initial component test of 20 minutes or so (oh, yeah, I did have to replace all the filter caps before I tested the amp).

Have fun-gus

GW

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