Any Ampex ATR100 experts out there?

[radardoug]

Working on an Ampex ATR100 which wont engage in ready mode. We have done a complete card swap with another machine, and so it is not the electronics cards.
I chased down a possible solenoid issue, but that was a dead end. The sensors on the two swing arms give odd voltages. The supply side swings +/- 3 volts, and the takeup side swings +/- 1.5 volts, so one over and one under the 2 volt spec. The logic outputs for the arm states appear to be right. Everything else has been checked and double checked. Anyone got any ideas?

 

[abbey road d enfer]

Do I understand the machine works in play mode but won't enter Record, or that it just won't start?
How is tape tension on both sides at rest?

 

[Brian Roth]

Awhile back, I had a problem with an ATR due to the fact the supply side rotary solenoid wasn't tightly attached to the "swing arm" with the half-moon-shaped PCB holding the sensing LEDs and the left hand roller.

One clue I had was the supply side roller didn't "clearly" move towards the head block when the machine was powered off. I observed the movements of the two tension roller assemblies on known-working machines. On the errant machine, the supply roller assembly barely moved at power-off, while the good machines obviously drove both tension roller assemblies towards the head block for a split second as the PSU powered down.

Bri

 

[radardoug]

Machine doesn't arm, so wont go into record. I'll check that one Bri, I was suspicious of one solenoid.

 

[Brian Roth]

Does one reel attempt to "tension up" but not the other? That was a symptom of the one I serviced.

Bri

 

[radardoug]

Hi Bri, thanks for the tip on power down. When I do that, the supply side kicks up markedly, but the takeup side not so much.
I've had that solenoid out because it didn't seem quite right. I suspect the centre has rotated some, so I will pull the middle out.
I found a picture in the manual that shows the armature as being at right angles to the output lever, so I will check that and let you know.

 

[radardoug]

Turns out the solenoid had rotated on its shaft, so posting this for future help. The machine now loads. However tensions are all wrong, and I think that is the photo sensors.

 

[radardoug]

Well after spending more time on this, it turns out both solenoids had rotated on their shafts. There is no visual clue to this, so you have to heavily disassemble the machine to get at them. I had changed the photo sensors too, but it turns out it wasn't them. The new sensors are not much different from the old in terms of voltage swing, and it turns out this doesn't matter much, as long as you can get a symetrical swing of at least 1.5 volts plus and minus. I have marked the solenoid shafts with a file and a black line indicating the internal position, so at least I wont get caught out again!
Posting this so hopefully others who have this problem can understand it. The sensors vary wildly in resistance, from 6K to 1K, so thats not much help!

 

[abbey road d enfer]

Glad you finally found out!

 

[RogerAF]

I remember servicing an ATR machine that turned out to have an erroneous resistor installed. This was on an unmodified board and was a manufacturing error. (The studio had about 5 of these machines and all the other boards had the correct value resistor.) When I eventually spotted this, I showed it to the owner and he said the machine had been working fine for several years. Once I changed out the resistor for the correct value, the problem was solved. I don't know why the machine worked for several years before having a problem. Just saying don't assume the factory did everything right.

 

[radardoug]

On this machine after getting it going again, I was checking record. In Input, the left channel was intermittent. It turned out the cal preset pot was never put in properly, with one leg bent over!

 

[RogerAF]

Well robots will get everything right every time. Until their stepper motors start stepping out. We're on the threshold of the bright future!
P. S. If you believe that, I've got some ocean front property in Nebraska for sale!

 

[Brian Roth]

On this machine after getting it going again, I was checking record. In Input, the left channel was intermittent. It turned out the cal preset pot was never put in properly, with one leg bent over!

After decades of use, I found that (even if constructed correctly from the factory) that the leads of the 10 (20?) turn trimmers used everywhere in the machine will experience a broken lead between the trimmer and PWA. It has to do with the fact the trimmers are behind a front panel and one has to "stab" with the adjustment screwdriver blindly. I am careful, but who knows who did what decades before I ever encountered the machine.

Bri

 

[radardoug]

You are right there Brian, but this one the wire never made it through the pcb.

 

[Brian Roth]

Doug....NO! It's not a pcb.........Ampex calls them a PWA Printed Wiring Assembly! <G!> Ampex folks will understand ;-)

I do have to say that Ampex wrote pretty decent manuals, BUT...

How to tear into the underside seems lacking. Or how to diddle/adjust those rotary solenoids and the stuff attached on the top side. Actual factory steps would have saved both of us hours of time.


Bri

 

[radardoug]

I found a drawing in the book which showed the roller arm at right angles to the armature, so I ASSUMED that was the correct position. Once assembled I put a file mark on the top of the shaft so you can see at a glance if they have moved. Ampex could have machined it so it couldn't turn, but they didn't. Ampex manuals are pretty good, and at least they provided manuals!