Ampex 440C 1" 8trk Capstan motor

[Echoplex]

I have a 400c 1" 8trk I've restored, clean, touch ups, new electrolytic's in the channel cards, transport, power supply motor caps etc. I have the DC motor with this deck and it is my understanding the C models only came with AC capstan servo motors. So that is confusing. My question is on the roll around under the transport by the fan (left side) there is a factory sub chassis (steel yellow zinc plate) about 3x5x5" with a small transformer on the outside and one Cinch cable that comes out of the box and goes into the transport. The sub chassis has access pots you can adjust. Any ideas? Is that anything to do with the AC Servo Capstan? I can't find a part number or description in my 440c manual. I'll try and get a picture

 

[Echoplex]

 

[sweetbeats]

No such thing as an AC servo capstan…it’s AC hysteresis sync.

The AC motor was an option on the 440C. The DC servo capstan was standard.

That box I think is the servo power supply but I’m not sure.

 

[sweetbeats]

The box may also be the servo assembly with the power supply. To what socket on the control box does it connect?

 

[Echoplex]

The box may also be the servo assembly with the power supply. To what socket on the control box does it connect?

Hey Sweetbeats! Oh right, I get the two motors AC/DC mixed up. So the cable goes to the transport chassis though a small hole and grommet. Here is a picture of the underside of the box.

 

[Echoplex]

There are two Allen Bradley pots (the best back then) you can tweak. I never have. This deck has the AC hysteresis sync motor then with the fan blade and it has a porcelain sleeve for 30ips operation. The previous owner explained that the servo was removed and the porcelain sleeve (according to him it was one of the best sleeves) was put on the replacement motor.

 

[Echoplex]

I have the 1981 Ampex 440C manual hard copy my understanding it was the last issue and I cant find any mention of this box. But this is a 440c 1"8trk and I cannot find the supplemental manual for the C only the B from 1969. Was there a C supplemental for the 1" 8trk?

 

[Echoplex]

Deck after deep cleaning, paint touch ups etc. See the 1" 8trk B manual from 69. The box on the back looks exactly like mine from the grainy picture but mine is not mounted on the back and is factory mounted under the transport.

Next the wire with the cinch plug goes into the transport (see picture) chassis hole on right. And note the transport chassis on mine on J602S says Servo motor not capstan motor like the B supplemental manual. It does have the same 6 pin cinch females chassis mount plug.

 

[Echoplex]

the circuit board in my small sub-chassis box has the same part number in the supplemental manual 4050500 "torque delay card" . I think?? they just changed the location of the torque box on the C machine. I'd like to put the original Servo motor back in as this deck had one to start.

So now my questions are.

A: did the 3/34ips-30ips servo motor on the C 440's just plug into the same 6 pin location as the B machine (this location has different language "Servo Motor" not "Capstan motor"
B: was the 440C 1" 8rtrk transport factory upgraded to accommodate the servo motor without the B servo optional upgrade kit? I assume so...
C: was there ever a 440c 1" 8trk supplemental manual printed?
D: Does this torque delay ever need adjustment on the two trimmer pots or was it factory set? (My transport behaves fine FWIW).

From the B 8trk manual:
"Modifications to the basic AG 440B machine to 8 track include the additional four channels, changes to the tape transport control box, the addition of a torque delay box, the addition of a power boost assembly, and an additional power supply. For improved ventilation, a fan has been installed below the tape transport. Following are the changes which have been made to the control box circuitry. (Refer to Figure 16, Dwg. No. 4840184, the revised tape transport wiring diagram. See also Figure 2, 3, and 4. ) 1. 2. 3. 4. 5. 6. Resistors R604 and R605 are now 35 ohms, 55 watts, variable to 10%. Line power fuses F601 and FG02 are now 5-amp Slo-BIo fuses. Receptacle J604S on the control box chassis, previously available as an input for a GO Hz amplifier, now receives the cable from the power boost assembly. The reel size takeup and rewind switches are not functional on the AG 440-8. The position of these switches is of no significance, since they are internally by-passed. Resistors R606 and RG08, the small reel takeup and supply tension adjustments, are not functional. Fixed resistor R610 has been added in series with R604 and R605. The Torque Delay box is mounted on the rear of the console and delays the torque to the supply motor until the tape is up to speed. (See Figure Cl 18)"

 

[sweetbeats]

The AG-440C-8 has its own manual, as it should. The earlier versions had a supplemental manual to be partnered with the standard 1/4”~1/2” AG-440 machines. Here’s the AG-440C-8 manual:
https://www.torridheatstudios.com/A...aintenance Manual (June 1974, 4890332-01).pdf

You’re welcome.

That box…from the blurry picture of the guts of the box I was able to read the p/n off the PCB and, looking in the manual above, I find that is the torque delay module. The AG-440 was never designed to handle 1” tape…none of it. It was a kludge. So there were things they needed to glom on to it to get it to work acceptably well as far as tape handling. In order for it not to take forever to reach proper speed in PLAY, the torque delay module effectuates a delay in the holdback tension of the supply reel motor, so the capstan drive and takeup tension aren’t working against that when you go from STOP to PLAY. There is also torque boost module that gives the takeup motor some extra juice at the same time…that’s the big box smack in the middle of the underside of the transport where the signal electronics power supply usually goes on a standard 1/4”~1/2” AG-440.

I hope, when they removed the DC capstan and retrofitted the AC capstan, and put the sleeve on the shaft, they did what was necessary to ensure proper switching occurs in the signal electronics for proper EQ curves for 30ips, and that the proper daughter boards and components are in place for this…so your speed switch still works, right? You can run it at 15ips and 30ips? Don’t have any documented response curves for the machine?

I don’t think I’d ever operate an AG-440 or MM-1x00 machine above 15ips. They don’t generally have the capability to really take advantage of the potential increase in HF performance (limitations in the head construction) one would get at 30ips, which is one of the reasons people run the higher speed, except for maybe the latest generation of MM-1200 machines? But the bigger issue is the loss of LF performance…when you double the speed it shifts the response curve up an octave. The AG-440 and MM machines, particularly the machines with the wider track format (like your 1” 8-track, as opposed to the 2” 24-track) are famous for the LF head bump and what it does to source material like drums and bass…it’s in the wrong spot at 30ips. You do get some signal to noise ratio benefits at the higher speed, but IMO the detriments at 30ips outweigh the benefits on a machine like yours…minimal HF benefit, tape costs double, lose the LF shizzle…Food for thought. To quote a friend of mine, “Set it up NAB at 15ips and it’ll sound like an Ampex.”

 

[sweetbeats]

I just saw your latest post. Can you please read/study my last post above and repost what if any of your questions remain?

 

[Echoplex]

Hey, Awesome thank you for the 74 version!! Okay so good stuff here!

So its a torque box, mystery solved thank you!

So yes the the small daughter EQ cards were switched for the 30ips option. And yes it will do 15/30 but I prefer 15ips. I'd like to put the original servo motor back on but I wanted to figure out if there was any mod needed for the C deck or was it just a matter of swap out the the motors assuming you have the 3ips cards. Or in my case they put a sleeve. I assume if you got the servo C option that would do 30ips it came with the daughter EQ cards.

I've done a fair amount of recording on the deck and I personally have not had any transport issue or ran into issues of the deck being not strong enough for 1". It seems to have plenty of get up and go and is smooth, frankly it speeds like a demon on FF/RW. I never use "STOP" in fast rev/for motion to avoid brake wear and tape snap, I just toggle the FF/RW until it slows down. I did have a power loss once on the take=up reel motor and had to replace the large motor cap. I just replaced them all for good measure and its been fine since. Back to FF/RW hauling ass.

 

[Echoplex]

Aha, so this large box "servo box" I do not have on the back of the unit. That is missing. So beside the servo motor I must need this as well. I wonder where this plugged into. I will not refer to your 1974 manual deeper. I want to solve this mystery.

I'm also going to look close at the back of my deck and see any signs of this ever being mounted on it. If not then the story I heard (that it had a servo) when buying it may not be true.

 

[Echoplex]

Yes just took a look on the back of the unit, you can clearly see the faint outline of where the servo electronics unit was mounted, so they story I got was accurate, someone removed the servo and switched to the AC capstan with the sleeve, this would explain why it already had servo speed daughter cards. I'd like to put this unit back to what it was and the extra servo speed accuracy would be welcome. Do you have a servo electronics unit

 

[sweetbeats]

I haven’t owned an AG-440 for about a decade and a half…I might have some random parts somewhere around here but certainly not a hen’s tooth complete servo motor setup. I wish you luck. The DC capstan didn’t necessarily provide better speed control. It provided the ability to interface primitive sync setups, which are truly not worth the effort, and it provided access to 4 transport speeds. It’s more complex and more difficult to repair. Also more rare. The original may have failed, driving the swap to the AC setup…much simpler, motor is much easier to rebuild, it locks to the AC power frequency, which is quite accurate…and you’ve already got the 15/30ips option with a nice porcelain sleeve. Ideal setup if you want access to the 30ips on an AG-440 and don’t otherwise need the DC setup, which you don’t. I’d leave it alone.

 

[sweetbeats]

And I wasn’t saying the AG-440-8 can’t handle 1” tape, I’m saying ghe AG-440 transport wasn’t designed to do it, and they had to add components to it to get it to operate acceptably with 1” tape vs being designed from the ground up to handle 1” and 2” tape like the MM machines. The deck plate wasn’t engineered for the 1” tape either. It works. I’m not saying it doesn’t work. It’s just been factory modified essentially to get the job done.

 

[Echoplex]

Yes you're right, its totally setup for 30ips and works fine. I used the 30ips option for one album project, to pricey and less bass goodness! I'd just like to see it back to what is was factory, it's the bad completist part of me LOL! My last upgrade was all new capacitors, motor caps and balancing transformers for the channel electronics.

Copy that, I totally understand. Yeah I've just read a couple people say in old threads the 1" 8trk was not as smooth on the transport but it's never been an issue and operates as smooth, fast and reliably as my 1/4" Ampex 440C. My only complaints are no counter and the 440C winkie channel repro/record switch windows (albeit cool looking) are hard to find and replace, so I bought a case of them that I found green and orange for lifetime supply.

Please do dig around and let me know what you might find. It would be cool to get it back factory stock for fun but for now it works flawlessly.

 

[sweetbeats]

I don’t think you understood what I was saying. There’s no way there’s a DC motor setup here. I only have a few small AG-440 bits and pieces. You’re going to have a hard time finding a DC setup, and it will be $$$, and may need repairs…and those will be $$$. I wish you luck.

 

[Echoplex]

Copy that, and thank you.

 

[sweetbeats]

In case you didn’t know the C has later gen heads on it with about triple the number of laminations (thinner laminations) and better HF performance to go with it. The earlier generations sound great but the C has that edge.