Ampex MM1100 restoration

[harry]

Hey Guys,

I've got an Ampex MM1100 16 track 2" that I've had for a while with the intention of restoring to working condition..

I was hoping to glean some information from those of you that have similar MM1100 / 1200 machines..

When I purchased it, I was able to play back tapes correctly (just a dead channel to sort out).
Transport worked fine and voltages checked out perfectly on the power supply (15v, 27, 39v)

I did not hit record at that time (2 years ago) as I read that there is a tantalum capacitor (C32) on each record card that is directly connected to the record head - and as we all know, when a tantalum fails - it shorts, therefore in this case taking out the record head.. I'll get to replacing those tants soon.
Upon firing up today, my transport would go into FFW when I pressed play, then the 30ips light went out and nothing... I could hear them motors tensioning (brake on) - upon probing the test points (the 15v) made things go funny - has any one got experience with bad test points / trimpots on the power supply cards. Probing the 15v made everything okay temporarily.. but my 15v is sitting at 3v instead of 15v. I switched it off in case it takes out a MDA power transistor.

So I've possibly got intermittent trimpots and probe points to replace (maybe a cold solder joint) and possibly a blown power transistor.

Wondering if any of you have come across these issues with your Ampex, or if anyone might have a cache of suitable transistors lying around in case my tech finds that they need replacing (i'm not game to work on the PSU)

I'll probably re-cap at least the channel cards and possibly the PSU, so if any of you fellow MM1100/1200 owners are game, we could combine a mouser order for those Axail Caps that are so hard to find in Aus.

Help me find out if this washing machine is in fact the sonic 'promised land' I think it is...?

[Sammas]

I have zero experience with ampex tape machines... but for anything big and old, overhauling the PSU is the first place I would personally start. All kinds of funky stuff can happen as the heat and load starts stressing what originally measured as in spec (at least voltage-wise).

If it hasn't seen a good service in its life, replacing the PSU capacitors (the small ones - pull a few big ones and measure to see if they are still in tolerance), fuses, regulators/transistors, diodes & bridge rectifiers, blasting dust out of the heat sinks, cleaning edge connectors, etc will put you in a good place to start on sorting out the rest... saves you chasing your tail as you move through the channel cards, etc.

Trim pots and capacitors don't like doing nothing for long periods of time. Sorting out trim pots can be as simply as exercising them back and forth a bunch. Electrolytic capacitors need some time to reform if they haven't been used for a while.

Does it have a dedicated ground test point?

[harry]

Hey Nath,

The tech came over today to grab the 15v/27v power supply (voltages are low) and the MDA assembly.. The reel motors go into spin on power up which would indicate blown MDA transistors possibly.. i'll know shortly..

As you said, I'll be working from the power supplies outwards. All of the contacts will need to be cleaned and connectors possibly replaced (molex's and cinch jones) to ensure connectivity, otherwise i'll be chasing my tail as it works one day and not the next..

What I do know is that all of the channel electronics work as expected (bar 1 channel) the heads are good, transport worked right until last power up...

As you said, now would be the time to re-cap where necessary (i'll save the power supply re-cap for my tech, and do the channel cards and card racks myself)

[mylesgm]

This guy has loads of experience with tape machines and has just arrived in Melbourne. might be worth an email...

http://www.gearslutz.com/board/australi ... hines.html

Bruce(at)brucemaddocks.com