Phonoland

My 1967 mm1 had static while adjusting volume that would end when desired volume level was reached.
Last use, the sound quit and has nothing.
All other functions work properly except sound.
Could this be a simple fuse or more complex as volume control unit?
Any suggestions / prior experience with problem would be helpful.

Thanks
Jack

More info needed--like which amp is installed in that MM-1 --tube type or"solid state" ?
If tube type--are all tubes lit ? Either type--is the AC plug in tight in the socket--is it "making contact" (these are prone to failure !) ? Ron Rich

Hello Rich
My unit is solid state.
The ac is secure.
When a record is put on the turntable and the needle makes contact there is a " pop" sound and a humming sound through speakers that is not affected when the volume knob is turned.

As per PM--Please add "USA" to your profile--
The "hum" would indicate a failure in the amplifier-I suggest it be dis-connected, and sent to a qualified person for repair, before more damage is done ! Ron Rich

All amps in the MM-1 were S-S. Tube hybrids did not appear till about three years later.

The MM-1amp has so many stupid errors of design that I wonder how so many of them lasted as long as they did. This was Rowe's first transistorized amp

To cut to Jack's problem. Set the machine to the play mode but with volume at minimum. If after a few minutes the heatsink is warm or hot. you have failed diodes in the primitive bias circuit. Most likely on one channel. Look under the chassis for two 5amp-fast blow fuses. Normally if outputs short these will blow, but if the amp was running hot for a long time some a-hole may have placed larger values there.

If little or no warmth is noted, the problem is at the lower current stages. Often this is caused by a failure of the small "dynamic filter" transistor.

I have two of these amps in commercial service. With some modifications it is possible to get better sound and reliable operation. An amp of this age MUST be rebuilt at least regarding capacitor replacement.

MM-1 Stupid Design Failures:

1) Amp mains (AC) is switched -between- records.

2) Finals bias 'regulation" is done by common diodes with no thermal connection to the output devices.

3) Muting is done by a relay --that shorts the output to ground--.

Jack, at this point you need to asses what you are capable of doing yourself and what is better left to others. In any case you should have a service manual.
http://www.alwaysjukin.com/items/servic ... s/list.htm OR http://www.victoryglass.com/

Rob/NYC

Rob,
I have seen these and other models "retrofitted" with tube amps--"Gepppetto work" ?
Ron Rich

Ron, yep, that would have to be a 'conversion" of some sort. The amp pan and mounting dimensions are different than any other Rowe amp -at least of that era.

I did mod one MM-1 hideaway to use the hybrid in fall 1987. It was going into a high-end cafe and I couldn't stand the sound of those old S-S amps. I installed the P.A. section on a scavenged mounting plate where the MM-1 amp would be and extended the preamp module's cable to mount it on the left side wall of the cabinet. Worked well -the location didn't. By the time I reused that hideaway for wallboxes i had improved the original amp to the point that it was acceptable, so back it went.

I like the fact that AMI-Rowe used metal hideaway cabinets. No matter how awful the previous location conditions were, you just strip them out, wash-repaint and out they go again.

Rob

BTW: I see you had a 'quake in the region. I believe you are on the other side of the Bay, but hope all is OK.

Hi Rob,
Yea--we had a little shaker yesterday--no damage here, just one "scairt (six month - old-sixty lb.) puppy dog"--as I am about 60 miles from the center--Thanks for the concern--
Ron Rich