MM HD130 Bias Question

CitiznesRepair

I have an HD130 head on the work bench. Chassis number 2275-130. It has the 12ax7 phase splitter, but also appears to have the SS drive board. Which bias method applies here?

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MM 2-10-65

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11 years 2 months
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mm210 Tue, 05/23/2017 - 02:56

Uh, neither. It never CAME that way. MAYBE the tube was just left in place but was converted to SS? Maybe post a good pic of the chassis and we can help. Mike.

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Charlie Russo
Music Man Equipment
HD130

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8 years

CitiznesRepair Wed, 05/24/2017 - 17:26

I think you are correct. It looks like the solid state board was added later, but they left the tube in place. The 12ax7 filaments are still wired up, but that's it. Best I can tell it's just a fancy light bulb at this point.

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MM 2-10-65

Member for

11 years 2 months
Profile picture for user mm210

mm210 Thu, 05/25/2017 - 15:41

Kind of wondered about that. I converted one from tube to SS driver but took all the chit out. Then LATER, went back in and converted it BACK! Geez, I'm an idiot. Dropped some dykes in it while running and the smoke leaked out! Never HAVE gone back and fixed it. Don't need a 130 watt amp anymore! Mike.