AMPEX gurus out there? MM-1100 trouble...Bo??? (update#1)

[amorris]

If you are new to the MM series, there are a couple of silly things that will leave you high and dry on these machines. there is a varispeed socket in the back that has to have two pins shorted(pins 1 and 2? not sure, call mike spitz at atrservice.com).it is the oscilator(9.6K?) that is sent out then needs to feed the capstan circuit.
also the light bulb under the tension arm needs to be operational for play. Mike Spitz at atrservice.com is the Ampex guru.

 

[Bo Hansen]

Jesus,

The advice from Amorris is very, very good to check that the dummy plug in the variable speed connector J1 on the rear accessory panel stlil are in place, if it is missing you can link pin 1 and 2 together as Amorris say, with out this link, the capstan motor can not run.

Also the lamp bulb for the tension sensor arm that you can find under the cover fit with one screw, is very important for the tape transport function, this is a 28v/0,06 amp lamp, (the feed voltage to the lam shall be 27 volt) and the lens and cover must be fitting before you can run the tape transport.

Regarding if there are relay`s in the MM-1100 tapetransport, no there are no realy`s in the transport, but ther are a lot of relay`s in the audio section.

The tapetransport are build with one of the first "MHTL" logic circuit`s from Motorola type MC-600 series and this is not easy to find on the market to day, then they use darlington power transistor (MJE-1100) to switch (sink) the ground side on all solenoids for brakeas, tape lifters, pinch roller and so on.

So if the pinch roller solenoid still not work, check the Q15 darlington transistor on the transport PC-card.

Regarding that the take up reel will spin uncontrollably, early you have say that you have change a lot of transistors and components in the MDA motor drive amplifiers.
You must be 100% sure that the MDA functions is ok before we can go further and search for this fault.

Here is some check to do:

1. With the end of tape arm activated and the machine in stop mode, can you regulate the spin of the supply and take up reels if you turn the tension arm up and down.

2. With the end of tape arm activated and the machine in stop mode, can you regulate the spin of the supply and take up reels if you adjust the R3 stop supply and the R6 stop take up preset potentiometers on the transport card.

3. Do you have a transport/capstan extender card ?? (normal it shall be place until the transport card in the extra slot if there not are a digital counter card there)

--Bo

 

[PRR]

> contact contamination from 'pot' smoke

Hmmm. But this apparently only affects the audio.

> The fundamental design of the transport etc did not change with the MM1200

And the things Crown did with relays, this does with those new-fangled unreliable transistors. It is still a "stuck relay", except you can't look at a transistor and see if it is stuck.

Assuming this to be true, and considering your gross problems, I would start with the Big Stuff:

The take-up system is an AC power winding, an AC motor, and this odd rectifier/transistor rig to reduce the current in the motor. Same for supply-reel, and similar for capstan except a DC motor.

If CR101, Q101, or Q102 are shorted, the takeup motor spins full-power. If they are open, it will never spin. These parts get huge abuse: assume they are blown (open or short) until proven otherwise.

If these are all OK, then they are getting bad signals from the controller card. Bo wants to see the card checked first; I would check the big stuff first. He has experience with these specific machines, I'm just a crude Ford mechanic.

Shorting pins 5/6 to 8/10 will run the capstan motor up to maximum speed, which is probably BAD for the motor. I'd try shorting with a 100Ω resistor for a very quick moment to see if the capstan starts to spin. That proves the power supply and motor are happy. If you cut the wire to pin 9 and connect transistor Bases to Collector with a 10K resistor, again it should spin: if not, transistors bad.

 

[Bo Hansen]

PRR,

Thanks for your help, this teamwork is necessary if we shall find out some advice for Jesus so he can find this fault.

I have work a lot with this old Ampex MM-1100/1200 but it is 15 years ago, so my memoary are not updated longer.

Any way, here is three issue of the MM-1100 MDA amplifier that have be use under the years, and if this is a very old 8 channel machine I think it is the issue-1 alternative.

http://w1.316.telia.com/~u31641623/MM1100%20MDA%20issue%201.jpg
http://w1.316.telia.com/~u31641623/MM1100%20MDA%20issue%202.jpg
http://w1.316.telia.com/~u31641623/MM1100%20MDA%20issue%203.jpg

--Bo

 

[bradzatitagain]

Mia culpa guys, & Jesus, I've been picturing the 1000 in my mind's eye this entire time which uses the same electronics as the 440 machines, & not until I found Alastair's comments to post did I realize the transport was the one similar to the 1200. Doh!

Jesus, I'm betting you could scrounge up an extender card from the guys on the Ampx list, or call Wayne Gunn in Palm Springs @ Audio Village, Voice: (760) 320-0728 Fax: (760) 320-2454. Here's his site: http://www.audiovillage.org/ and his e-mail: audiovlg @ gte.net. He's got an awful lot of stuff in general. If you're by Rubidoux he's not that far from you, you know, Joshua Tree.

rgrds,
Brad

 

[ladewd]

PRR has a good point. I had a 1200 which had a shorted rectifier causing the reel motors to run away.

Definitely something to check.

CA

 

[sverige_cruz]

WOW! You guys are great! Thanks for lending your minds & learned thought. No work this Thursday, so maybe I can get over to my friend's house and check it all out.

Brad,

I'm betting you could scrounge up an extender card from the guys on the Ampx list

We have one, and had been using for the transport control board.

good to check that the dummy plug in the variable speed connector J1 on the rear accessory panel

Yes, got that too. Connected correctly, but I'm not sure if it's putting out 9.6kHz...maybe I'll drag along my scope. I had read in the Ampex archives, that people used to hook up a signal generator to old McIntosh amps and use that as a vari-speed.

PRR & Bo, thank you. I will definitely look into the sections you posted about.

I think my friend said he had talked to Mike, at Audio Village, a while back, but it was too much $$ for a teacher's salary, at the time. That's why this place and others like it are so valuable. So much information and guidance.

Again, I can't thank you enough. I'll keep you posted.
Best Regards,
Jesus

 

[bradzatitagain]

Jesus, Here's a manual, don't think it's too much $$$$$:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=15199&item=3765113767&rd=1

If I were you I'd bid on it. Sniper the thing, y'know? Any more luck lately?

rgrds,
Brad

 

[sverige_cruz]

Hey Brad,

Thanks for keeping an eye out! I actually was fortunate enough to get a pdf from one of the Ampex-list guys. So, if anybody needs a 10+MB manual file for an mm1100 you know where to look.

I've been emailing Bo, recently (didn't want to clog The Lab-Waves), and testing the MDA extensively... getting mixed up with the revisions schematics and the version I have. Turns out it was either the 1st or the 2nd, but upgraded at a later time to the 3rd. So far, everything checks out, but he also suggested another thing to try out...just got to find time.

Thanks again,
Jesus

 

[bradzatitagain]

Jesus, how much did you pay for the deck, if you don't mind my asking?