Pre-Ernie Ball Music Man Amps

Can you tell me if there are any authorized service centers that will still work on the old Music Man amplifiers?

Music Man HD-130. Chassis number 2475-130. It did not come with the Reverb/Vibrato RCA foot switch.

I am the proud owner of a 70s Music Man HD-130, chassis # 2475-130. I'd like to replace the tubes and bias the amp myself, but I don't know much about the amp except it has 4 x EL-34s.

Chassis number 2475-130, Music Man HD-130. The Vibrato Channel is getting weak and I believe it is the power tube going bad.

I'm looking for some MJE1692 transistors for a MusicMan RD-50 guitar amp and they seem to be very hard to find. Do you still have any of these? If not, do you have any suggestions for me?

Can you tell me if my HD 130 amp needs a bias adjustment when the power tubes (EL34's) are replaced? I looked inside and I do see two blue dials on the pre amp board, but those are the only things that looked adjustable to me.

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