Music Man HD130 Reverb - Tremolo Trouble

adam79

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Jan 27, 2010, 6:24:37 PM1/27/10

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The tremolo effect stopped working on my Music Man HD130 Reverb head.
The head wasn't dropped or tinkered with, which makes me curious as to
why it isn't working. The reverb still works, and the footswitch can
still engage and disengage the tremolo. When off, the amp plays fine,
when clicked on, the amp gets a bit muffled, and when the tremolo knobs
are moved the sound starts to break up and crackle. Anyone have any
suggestions on a fix? I don't have the money to bring it into a tech.

Thanks,
-Adam

Phil Allison

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Jan 27, 2010, 7:55:52 PM1/27/10

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"adam79"

>
> The tremolo effect stopped working on my Music Man HD130 Reverb head. The
> head wasn't dropped or tinkered with, which makes me curious as to why it
> isn't working. The reverb still works, and the footswitch can still engage
> and disengage the tremolo. When off, the amp plays fine, when clicked on,
> the amp gets a bit muffled, and when the tremolo knobs are moved the sound
> starts to break up and crackle. Anyone have any suggestions on a fix?

** Try removing the tremolo FET from its ( plastic push in ) socket and
cleaning the legs with a fine wire brush - IME they can become tarnished
after 30 years, going almost black and ceasing to conduct.

> I don't have the money to bring it into a tech.

** Bullshit.

... Phil

adam79

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Jan 27, 2010, 10:00:52 PM1/27/10

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Phil Allison wrote:
>
>> I don't have the money to bring it into a tech.
>
> ** Bullshit.
>

Thanks for the tip, and your hilarious closing zinger.

-Adam

adam79

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Jan 28, 2010, 3:28:15 PM1/28/10

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Phil Allison wrote:
>
>
> ** Try removing the tremolo FET from its ( plastic push in ) socket and
> cleaning the legs with a fine wire brush - IME they can become tarnished
> after 30 years, going almost black and ceasing to conduct.
>

What does a tremolo FET look like? I'm assuming I'll have to get the
schematic to find where it is on the board, unless it's somewhere near
the tremolo rate and intensity knobs..

Thanks again,
-Adam

Phil_S

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Jan 28, 2010, 3:45:49 PM1/28/10

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"adam79" <ada...@toast.net> wrote in message
news:rpCdnTZsk-79bvzW...@posted.toastnet...

LOL! It's Bobba Fet's cousin!

Dave Curtis

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Jan 28, 2010, 7:04:09 PM1/28/10

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And don't use a wire brush, no matter how fine it is. Don't use
anything abrasive to clean metal contacts. Caig Deoxit or ProGold is
what you need for that. Often all it takes is removing them and
reinstalling them, if that's what the problem is.

What's you're chassis number?

If I have the right schema, the oscillator is a 2N3391 and the FET is
the 2N4091

jh

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Jan 29, 2010, 1:19:10 AM1/29/10

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adam79 schrieb:

adam,
although the procedure itself is not that complicated, but don't forget
about the potentially lethal voltages lurking in a Musicman.

CAUTION
It might even possible, that these voltages can be stored, when the unit
is shut off and disconnected from the mains.

AND if someone appears saying the MMs have bleeders - yes - but I've
also seen failed ones. Then the lytics can stay charged for weeks

Disconnect
Open
*Measure*
Measure
do your job

Jochen

adam79

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Jan 29, 2010, 3:17:28 PM1/29/10

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Where is the chassis number located? I opened the back (didn't pull out
the chassis) and noticed that there is a leather pouch that is screwed
in, and the reverb/tremolo switch goes into it. I'm assuming that's the
reverb tank and tremolo unit. That's where the FET will be, correct?

I have DetoxIt Contact Clean, and also the lube. When I have the time,
I'll take out the chassis and effect unit and take some pictures.

Thanks,
-Adam

RD Jones

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Jan 29, 2010, 10:18:30 PM1/29/10

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On Jan 29, 2:17 pm, adam79 <ada...@toast.net> wrote:

> Where is the chassis number located?

Chassis number alone will not identify which circuit variation you
have.
The presence (or absence) of a phase inverter tube will get you
closer,
but many of these were "field modified" to update the circuit.

> I opened the back (didn't pull out
> the chassis) and noticed that there is a leather pouch that is screwed
> in, and the reverb/tremolo switch goes into it. I'm assuming that's the
> reverb tank and tremolo unit. That's where the FET will be, correct?

No.
You REALLY should consider hiring a tech before you damage the amp
or worse, electrocute yourself.

> I have DetoxIt Contact Clean, and also the lube. When I have the time,
> I'll take out the chassis and effect unit and take some pictures.

Well over 700 volts in these amps, please use caution.

rd

adam79

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Feb 2, 2010, 4:37:46 PM2/2/10

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Thanks for all the advice. It turned out that the speaker cable was
causing the problem. It's odd how it just affected the tremolo at first.
Thankfully I won't have to bring it to a tech, and spend money that I
don't have!

Thanks again,
-Adam