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Ampex mm1100 superspeed mystery
Old 1st December 2012
Here for the gear

Ampex mm1100 superspeed mystery

I've just aquired a lovely 2" Ampex MM-1100 16track in good shape. I suspect its not happy from being shipped as I know its history and it is overall a very stable unit (for an old ampex). But I'd prefer that it run at 30ips instead of 230ips when I put it in PLAY (almost the speed of FFWRD). Anyone have suggestions on the likely culprit?
The pinch roller is engaging properly, tension bar at 2", so far no broken traces or visible component failure on any cards I have pulled, dummy plug seems to be seated normally. I'm recording in a log cabin in the middle of nowhere so I don't have the option of having my more knowledgeable friends drop by and point out what may be an obvious problem. So any advice much appreciated. Cheers.
Old 1st December 2012
Gear Addict
Avast!'s Avatar

Probably one or more blown transistors in the Motor Drive Amp (MDA). That's a removable unit in the lower left rear of the deck... lower right if you're looking at the back of the machine. I'd sorta suspect the two 2n3055's in the MDA that are on the same side as the take-up reel...

Does it fast forward, rewind, and stop normally?

Also, make sure that the light bulb under the tension sensor cover on the top left of the machine (left-hand springy guide) is lit.

Good luck!
Old 1st December 2012
Gear Nut

I concur with Stuart.

Do a full tension alignment. You will know if you have an MDA problem as soon as you try to normalize the tensions.


David Ollard
Thin Brown Line
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