Music Man RD 110

[lowell]

Any help appreciated.

[oc disorder]

There is lots of useful infomation about Music Man amps at
http://www.musicmanamps.com/

An RD 110 from their site is
Series 50 RD (Single Channel) 1982-84 110RD-50
Chassis 1650-RD
Speaker 1-10 Ceramic
O/P power 50 Watts RMS
Tubes 12AX7, 2- 6L6GC
12AX7 used as a limiter, w/Limiter control

http://www.pacair.com/mmamps/schematics/index.html
Schematics :-
Gif (zipped)
http://www.ernieball.com/mmonline/te...ps/1650-rd.zip
or
PDF
http://www.ernieball.com/mmonline/te...ps/1650-rd.pdf

Hope thats of some help.

[TomCarlos]

I found the schematic that has the 12ax7. I believe this was a mid-70's version of the amp. Here it is. Tom

[soundguruman]

Any help appreciated.

A lot of times the amp is fixed by replacing Q 3 and Q 4.
Making sure that Q3 Q4 is properly insulated from the chassis. And that these have good heat sink grease applied...
and that the screws holding Q3 Q4, are nice and tight.
That is one of the most common failures in this amp.
Q3 Q4 can easily be replaced with TIP transistors.

The amp originally had thermo-pad insulators on Q3 Q4.
I don't like those thermo-pads.
I would rather use mica insulators, and heat sink grease.
I think those thermo pads go stale, after so many hours.

Another common failure is the high voltage coupling caps. Sometimes they short out.

HUM: 60 cycle hum in this amp
is frequently cured by grounding the speaker frame with a wire, to the amp chassis.
Depends on the speaker. Especially if the amp has an EVM speaker...
The amp (speaker) will even HUM with the standby turned off.
This is your CLUE that the speaker frame is not grounded.

I would probably say, that's the most common stuff, in a nut shell, from this nut.

Once you go over that stuff, it's usually a pretty good amp.

[TomCarlos]

Thanks SGM....

My friend has this same amp and will be bringing it by this weekend for a checkup. I think he's having some issues with the Reverb but I will certainly look at the items you mention above.

Tom