I have a couple threads started on the Olivetti motor, speed regulator, and telegraphic circuits. The reason is that I’ve had my suspicions about its (nearly) 150 baud operation. As far as I can tell, it should run at 110 baud...

eric F.

@ef1j95

10/5/2019, 3:49:23 PM

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eric F.

@ef1j95

Disassembling the power unit and telegraphic circuits proved that the machine speed is controlled purely mechanically in the teleprinter unit. This might seem obvious, but I have very incomplete documentation of the TE-318.

10/5/2019, 3:55:21 PM

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eric F.

@ef1j95

This is my best guess of what should happen. The motor has two coils operating on one phase with a motor capacitor. On startup, both the IC centrifugal and RV regulator switches are closed, bypassing the limiting and ballast resistors.

10/5/2019, 3:59:08 PM

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eric F.

@ef1j95

The IC switch opens first when the motor spins up. At (or slightly above) the set-point speed, the RV switch should open. Current is controlled by the ballast (RZ) resistor. FS and FM are the anti-spark and motor filters.

10/5/2019, 4:02:59 PM

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eric F.

@ef1j95

If the motor slows, then RV closes, bypassing the ballast resistor and causing the motor to speed up. The problem is that this switch never closes. The motor is always so fast that it remains open. Yet, the machine is running too fast.

10/5/2019, 4:07:41 PM

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eric F.

@ef1j95

My hunch was that the circuit was shorted, either across the spark filter or the ballast resistor. Once I had the regulator open, I could hold RV open (while powered off, natch) and test the FS contacts. The filter did indeed fail. But how to get it out?

10/5/2019, 4:30:04 PM

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eric F.

@ef1j95

Today’s discovery that I could pull out the entire motor assembly was the key.

10/5/2019, 4:33:13 PM

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eric F.

@ef1j95

Now I have to source a replacement for this ICAR filter with a January 1972 date code. But I think that’s all!

10/5/2019, 4:39:48 PM

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eric F.

@ef1j95

ICAR AR100.23

10/5/2019, 6:10:17 PM

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eric F.

@ef1j95

Looks like an RC snubber parallel to the RV switch, but also with two inductors in series. Could I get away with just an RC replacement?

10/6/2019, 2:15:19 PM

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eric F.

@ef1j95

Well, shoot! Here is a slightly younger version of the spark filter (1983 date). Doesn’t ship to North America, but it does give some details on the cap, resistor, and inductors. https://www.tekkna.it/product/24719/FILTRO-DI-RETE-ANTIDISTURBO-ICAR-AR100.23-240V.asp

10/7/2019, 5:52:21 AM

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eric F.

@ef1j95

11 bits in 100ms = 110 baud

10/9/2019, 10:08:50 PM

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eric F.

@ef1j95

But my hack snubber circuit in lieu of the ICAR filter doesn’t seem to work so well. Lots of sparks flying. Though, given the accumulation on the nearby centrifugal switch posts, this may not be a new occurrence.