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PostPosted: 06 May 2017, 16:27 
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Joined: 23 Dec 2014, 21:45
Posts: 11
I picked up this amp today at a hamfest and I'm a little confused about the OT. The amp says stereophonic, the pots are all stereo and has a 6CA4, 6BQ5, ECC83 and an empty socket looking down from the top of the chassis left to right. Based on the wiring it looks like the empty socket should also have a 6BQ5.

Where I'm stumped is it only has one OT but there are several wires going into it. It almost looks like a double transformer and I'm not sure what the transformer on the left of it is. I thought it might be a choke? I can't find a schematic for it anywhere.

Any ideas?


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PostPosted: 06 May 2017, 17:52 
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Joined: 04 Jun 2008, 20:59
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Location: Arizona, USA
Hi, Something that was done back then was to make both mono and stereo versions of gear. In the stereo one they had a second amp that either was slaved to the first one or fully independent. Another thing they did was put one amp section on the main chassis and the second channel on a separate one. That might well be what you have. The second socket could well be another 6BQ5 and the amp have a push-pull output stage. I believe I would put out a search for the schematic. it would greatly simplify things.

Good listening
Bruce

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PostPosted: 06 May 2017, 18:33 
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Joined: 23 Dec 2014, 21:45
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If you look closely at that OT there are the same (different colors) wires coming out of each side. I think this is a real stereo single-ended amp. I searched the 'net for two hours earlier today and cannot find a schematic that's even close.


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PostPosted: 06 May 2017, 19:30 
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Joined: 23 Dec 2014, 21:45
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I guess the best thing to do is draw the schematic out the way it's wired and see what's what.


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PostPosted: 07 May 2017, 19:11 
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Joined: 23 Dec 2014, 21:45
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Ok, so this schematic is very close to the way this amp is laid out. If I understand it, the two sides are out of phase with each other, like a pseudo push-pull system only being completely separate. There are some differences in the power supply as compared to a "standard" system but it looks to me like they were looking at space-saving by combining the chokes and OTs into one unit each.


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