Ampex MM-1000 Story...

In terms of the actual power I wold suspect that the light did not lite because the voltage dropped from the 100+ volts no load to something much lower. thus a much lower wattage.
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Ah. Right. The lamp becomes a voltage divider right? And I can put my meter between the household ground and the plate and watch what happens to the voltage when I connect the lamp in series, yes?

Perhaps disconnecting everything near it one by one without frying yourself or your machine will help find the source.
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Right...but that's also part of what is baking my noodle...there is one sole connector that interfaces the transport with the rest of the machine...it is J2, a round 37-pin amphenol connector. 14 of the conductors are used out of the 37. EVERY ONE OF THOSE 14 PINS IS CARRYING AC VOLTAGE...like between 11 and 33 volts. I posted detail up somewhere earlier in the thread.

So I can get the ill behavior to stop by pulling J2 at the transport. We know it is coming through there. I've tried disconnecting every transport component from the transport-side of J2, and the plate is still charged.

Doesn't seem to me that there should be constant AC voltage on those 14 pins nor does it make sense that it is getting to the plate if I unplug everything from the harness.

And it further doesn't make sense that there should still be AC voltage on all those pins if I disconnect the wiring harness from everything else in the machine, which I have done. I've taken the relay box, 24VDC supply and 39VDC supplies out of the loop as well as the control panel. I've even taken the internal AC power harness out of the loop (by making my own cable to go from the receptacle to the MM-1000's breaker panel). So that's everything. Its just basically wall receptacle to the transport connector J2, but if I measure for continuity between the hot and neutral legs coming into the machine and the plate there is zero continuity!!!

:(

Do I recall correctly that you measured little or no voltage between the protective ground and the neutral wire at the outlet you are using?
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Yes. And I'll check that again.
 
Pull the connector and measure the resistance from each pin on the transport plate side to the transport plate. Which ones have low resistance? These will be the ones to look more closely at.

--Ethan
 
Thanks, Ethan...that's all I need at this point. Just something, anything to do next. I'm so flustered by this that I can't think straight when I turn my mind to the MM-1000. Don't worry, guys, I'm functioning just dandy otherwise :), but I'm definitely frustrated with the MM-1000 when I see it or think about it.

SO...just to clarify: check the resistance from pin to plate with the transport components hooked up, yes?

Thanks.
 
sweetbeats said:
Thanks, Ethan...that's all I need at this point. Just something, anything to do next. I'm so flustered by this that I can't think straight when I turn my mind to the MM-1000. Don't worry, guys, I'm functioning just dandy otherwise :), but I'm definitely frustrated with the MM-1000 when I see it or think about it.

SO...just to clarify: check the resistance from pin to plate with the transport components hooked up, yes?

Thanks.
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THis sounds right - connector unconnected to rest of machine. Transport components connected up. Transport connector to transport plate.

--Ethan
 
Never underestimate...

Your ability to be a complete dumba**.

*sigh* :o

I've been measuring for amperage with the + probe still plugged into the socket for voltage on my Fluke 85.

Wow.

I'm really sorry to drag this thing on while grabbing at you all to help.

Totally embarrasing...yet relieving at the same time. I suppose quite like having to go to the bathroom so bad while hiking or camping that you end up going where you might be seen, and upon being seen you really don't care all that much because it feels so good to finally go...

Okay...

Just to be totally clear, the power path to the MM-1000 is (starting from the 50+ year old 20A breaker in the service panel):

  • About 40' of new 12/3 romex
  • New receptacle
  • Monster Power Pro 2500 power conditioner with a hefty 10' power cord connected to the above receptacle
  • 30' 16AWG extension cord connected to the Monster 2500

The Ampex is plugged into that extension cord.

At the end of the cord when I measure between the neutral and ground I get:

  • 105mV AC
  • 0mV DC
  • 0.4mA DC
  • 42mA AC

Now, plugging in the MM-1000 and measuring between the ungrounded transport plate and the household ground present in the Ampex's breaker panel (and note all components are connected as for normal operation) I get:

  • 106V AC
  • 0V DC
  • 0.5mA AC
  • 0mA DC

Heheh...about 0.05 watts. THAT would certainly explain why the bulb didn't light...

When I connect the transport plate to ground I get:

  • 0.1mV AC
  • 0mV DC
  • 0.02mA AC
  • 0mA DC

SO...

Everything look okay????

BTW, without my Fluke probes connected to anything it picks up over 100mV AC just in the environment.
 
Problem solved! Induced pickup it is I would agree. Ground that plate and then a fault will ground ouut rather than set it up as a death trap.

--Ethan

PS TMI RE Pee in the woods :eek:
 
TMI???

C'mon...you've all been there...in fact, Ethan's avatar looks like he's doing just that! :laughings:

Okay. This is great.

I'm going to run the ground to the 24VDC regulated supply that's in the schematics, runn a dedicated ground wire from the breaker panel to the transport plate, and I think it would be good to run a dedicated ground wire to the console chassis.

I wonder about the relay box and the 39VDC regulated supplies too...they both have AC line voltage going to them but I don't believe they are grounded...that goes for the electronics in the overbridge too.

What do you guys see in your systems in that way as far as grounding?
 
Don't go crazy with the grounds....

Your Ampex has 3 wires does it not? Hot, neutral and ground ?

The neutral on the Ampex power cord shold connect to the chassis metal somewhere. So just strap the transport plate to the chasses. It will then be protectivly grounded.

Missing ground wires most likely should be installed.

If you run a second ground wire fromt he panel to the plate you have set up a ground loop. each leg of the loop will have different paths (of course) and if one of the paths fails you could have different potentials.

Remember that the birds on the wires do not fry until they connect 2 wires.

--Ethan

Or perhaps I misunderstood you.
 
Ohhhhkay...no...you didn't misunderstand.

Hm...this is like trying to figure out the grounding in the M-__.

I'll have to look and see if I can find where the neutral ties to the chassis because, so far anyway, I haven't seen it physically or schematically.

So, I should be able to (with the MM-1000 disconnected from power) set my meter to continuity, clip one probe to the neutral line in the breaker box, then find a bare metal spot on the chassis, probe that and have low resistance continuity??

Wouldn't that mean if I was standing in a puddle of water and touched that bare metal spot with the Ampex powered up I'd be a goner?
 
The neutral on the Ampex power cord shold connect to the chassis metal somewhere. So just strap the transport plate to the chasses. It will then be protectivly grounded.
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Okay...going a little further. I need some clarification on what you said. Did you mean to say the ground on the Ampex power cord should connect to the chassis somewhere?

If so, I agree, but it does not. There is an attempt at it with that lug on the breaker panel, but because of all the painted surfaces that ground connection doesn't get past the breaker panel.

So "star" grounding could be bad. I understand the ground loop issue. If I run a ground wire to the chassis near the breaker panel, and then provide a bare metal contact at one of the places where the transport plate bolts to the chassis (there are three 5/16" bolts that secure the transport plate in its tray in the chassis, but again everything is painted so no continuity from chassis to plate, but if I removed a small area of paint at one of those attachment points and used a good star washer that would be an excellent continuation of the ground connected from the breaker panel to the chassis...)

If you really meant "neutral" should be connected to the chassis, the neutral comes into the breaker panel, goes out to the 24VDC supply, branches at the 24VDC input and goes to the 39VDC supplies where it gets rectified. The neutral that goes into the 24VDC supply actually goes through the supply (as well as being rectified) and on up to the relay box where it goes straight through on up to the transport and the reel motors and capstan motor. At no point does it connect to anything besides a transformer or a motor.
 
I dug out the schematics

The schematics show the ground wire connected to the chassis. Scrape off some paint and use star washers where required.

I keep getting caught up in the words. Breaker panel to me is the fuse box of your house.... Buss are all connected together and terminal strips are individual connections on a common insulator carrier.

Neutral should only be connected to ground in your houses breaker box. Hot, neutral and ground all run the same distance with the same wire type from your houses breaker panel to your Ampex.

--Ethan
 
Sorry to be muddling...

I used the term "breaker panel" as it comes straight from the MM-1000 manual. Its confusing. I should use a different term.

And, yeah, my bad. TB1 is a terminal strip, not a buss strip.
 
Corey, In response to your above signature -- No complete dumbass could accomplish half of what you've accomplished so far with the M-___, MM-1000 and other little monsters you're assembling :D
 
That's nice of you to say, Muck.

Yeah, I wasn't really thinking in terms of constant dumba**edness when I said that, but more a reminder that I have a good solid capacity to do really stupid stuff sometimes and if something is really weird I need to remember to step back and consider the *basics*.

I spent three frustrating hours once trying to get my tractor going...no fuel flowing. Turned out I'd forgotten to switch the fuel valve open.

In the everlasting words of Robin Wiliams' character on Good Morning Viet Nam, If the motor's humming, its already started (or words to that effect).

I mostly feel silly for wasting space on the forum and grabbing at others' attention for something that was simple and on my end. I'll never forget to check to make sure the leads are plugged in right though... :D

So the quote is just a reminder to not overlook the basics...and maybe not to take things to serious when I get frustrated. Step back and take a break.

And I've gotten a MUCH better understanding of the risks working around this stuff even though the risk was very low ( though it looked dangerous there for a bit).

BTW, you all may recall that the supply tension arm is missing the dashpot (a little two-way air shock that dampens the travel of the tension arm in both directions). Its a little precision deal. No luck finding used but I DID get the manufacturer, Airpot, to send me a free sample of one the should fit and perform like the original. Haven't tested the fit yet to make sure it will work and i'll need to do some minor mods to the linkage, but it'll keep the arm from shooting out and striking the outboard stop under certain conditions as its been doing.

I'll get to putting that in, get the grounding issue situated and then continue with the transport adjustments.
 
man what a beast of a machine! I cant beleive that you got it for that price!
Im sure that youll have many sleepless nights playing with that:D
 
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