Mesa D180

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Smokebreak
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Mesa D180

Post by Smokebreak »

Anyone familiar with these amps? I've got one coming up for repair, and I pulled up a scheme to check it out. Apparently there's no power section scheme to be had, as it was never released or something, and I guess no one has traced it. It's a 6x6L6 amp, with a driver tube, and a wacky Master. Preamp appears to be typical Mark I style cascading/clean deal via 2 inputs.
Anyways, I haven't even cracked the amp, but looking at the driver portion of the drawing, did they really take the NFB off the OT secondary(I'm assuming) and feed it back into the 12AT7, to get an inverted signal? I guess I'd never really even considered that a way to skin the cat.
boogie_d180.pdf
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martin manning
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Re: Mesa D180

Post by martin manning »

I've never seen one, but they seem to be well liked by those who own them. Only about 1000 were made, I gather. A quick look around the web only turns up the same partial schematic you posted above, so I can't tell where the NFB signal is taken from. You could trace the whole power amp out and perhaps become famous.
MARK1
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Re: Mesa D180

Post by MARK1 »

You may check the larger series like the 400
Smokebreak
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Re: Mesa D180

Post by Smokebreak »

martin manning wrote: Sat Oct 14, 2017 9:37 pm I've never seen one, but they seem to be well liked by those who own them. Only about 1000 were made, I gather. A quick look around the web only turns up the same partial schematic you posted above, so I can't tell where the NFB signal is taken from. You could trace the whole power amp out and perhaps become famous.
:D
Smokebreak
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Re: Mesa D180

Post by Smokebreak »

A forum member was nice enough to send me a hand drawn sketch. I will do my best to redraw it and post. But the other side of the driver circuit is indeed fed by a highly attenuated signal taken off the OT secondary
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pompeiisneaks
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Re: Mesa D180

Post by pompeiisneaks »

I'd be very wary of posting anything with the name 'Mesa' they've sent cease and desist letters to another forum/site for posting mesa schematics. The schematic being drawn by you would be fine, just don't mention "MESA" on there anywhere so they say your'e infringing on their IP. In my understanding, anyway.

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dorrisant
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Re: Mesa D180

Post by dorrisant »

Phil, you should delete your last comment. He he. You know... burn after reading.
"Education is what you're left with after you have forgotten what you have learned" - Enzo
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pompeiisneaks
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Re: Mesa D180

Post by pompeiisneaks »

Who was that, and what did he do with my account? ! :D
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sonicmojo
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Re: Mesa D180

Post by sonicmojo »

Whenever I need a MB schematic I usually just email their support line. They are very helpful and usually send one right away. Of course it is often what you can find on the web, but seeing as they are not hosted many places anymore, it is usually not a big deal just to ask them directly.
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Smokebreak
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Re: Mesa D180

Post by Smokebreak »

Yep I had some other MEsa in last month(that I really should start a thread for). The OT brackets were busted, and it was duct taped to the chassis. I can't even explain it, it was so ridiculous. Anyways, called MB and they sent out a direct replacement, and very reasonably priced. Plus , owner didn't want the old OT back, so I got to keep the iron, which I'll duct tape on one of my build, one day.
Smokebreak
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Re: Mesa D180

Post by Smokebreak »

Back to the D180. Owner bought this new in '83 I think he said. Never been serviced. Said it turns on but sound stopped last week. One of the preamp tubes had gone south. Simple fix but owner wants a full retube and cap job. Amazing the power tubes lasted longer than the pre tubes. I havent done the rest of the work yet but I bet they are biased coooooold.

What a great looking amp, here's some pics. Also of note, the tubes have a label underneath, that designates 12AT7 for v2, and v3, contrary to the schematic. Examination of the actual tubes confirms this.
IMG_1819.JPG
IMG_1818.JPG
IMG_1817.JPG
IMG_1816.JPG
IMG_1815.JPG
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Smokebreak
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Re: Mesa D180

Post by Smokebreak »

more
IMG_1820.JPG
IMG_1821.JPG
IMG_1822.JPG
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martin manning
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Re: Mesa D180

Post by martin manning »

Nice! Thanks for posting pictures... some interesting construction details there.
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