[GreenKeys] Model 33 Auto Paper Tape Reader Intermittent Start

[Mike Douglas]

Rob,

1) Is the reader mechanism itself manual or automatic (ignore the label on the covers) -- does your start switch stay in the on position when moved up (manual), or is the on position momentary (automatic)?

2) If you hear/see a relay on the reader power supply, then it is an automatic reader supply, so based on your comments below, I assume you have an automatic reader supply. Is this correct?

3) Does the connector to the reader power supply have a wire in every position, or just some of the positions?

4) When you say it "won't start," it sounds like nothing is happening at all -- the distributor doesn't release and turn and the reader itself doesn't feed. Is this correct?

Assuming an automatic reader, auto reader supply and auto reader wiring, and the primary symptom is that the nothing happens at all other than you hear the relay pull in on the auto reader, then...

For the automatic reader, the reader start switch does NOT directly switch current on for the distributor release coil. Instead, the start switch is part of a 48 VAC control circuit that is 1/2 wave rectified and filtered to energize the relay on the auto-reader supply. When the start switch is moved to the on position, the relay coil in the auto-reader supply is energized and one set of its own contacts then holds the relay coil on even when the start switch is released. This is why when you subsequently move the switch to the on position, you don't hear the relay click -- it is already pulled in. Move the switch to the temporary off position and you should hear the relay release. Then if you move the switch to the on position, you should hear the relay click again.


When the relay pulls in, another set of contacts closes the circuit to supply power to the distributor release coil. This is the contact closure that should get everything started. This is where we'll look for problems.

With the unit on and motors running, measure the AC voltage between J4-P11 and J3-P7. Is this 115 VAC or 48 VAC? If neither, switch to DC and see if it is 24 VDC.

With the unit off, remove the armature on the reader distributor release coil (the one with the plastic tip that hits the contacts under the "Caution High Voltage" cover. Look for labeling on the top of the coil. Is it 300M, 279M, etc.?

What type of UCC are you using? Is it a private line UCC-6?

These last few items will tell us whether we have a distributor release coil versus drive voltage incompatibility, or whether we should start digging further into wiring and relay contacts.

Mike







________________________________
 From: Robert Jarratt <robert.jarratt at ntlworld.com>
To: greenkeys at mailman.qth.net 
Sent: Sunday, September 8, 2013 5:13 AM
Subject: [GreenKeys] Model 33 Auto Paper Tape Reader Intermittent Start
 


I have made some great progress with my auto tape reader on my Model 33. It needed a replacement contact block as the original one was broken. When I replaced it I cleaned every single contact and checked continuity of all wires and contacts with my multimeter. Once I put it back together it worked, reading the tape and printing the characters.
 
However, I am still getting a problem where it won’t always start when I push the control lever to the start position. The problem is intermittent, although right now it is not starting at all.
 
As far as I can tell, the problem is not related to the contact wires controlled by the control lever. When I push it to the start position the contact wire creates the necessary short, and the other control wires create the expected open or closed circuits. When the problem happens, and I have not switched on the machine for a while, I can hear a faint click in the reader’s power supply when I operate the control lever for the first time. If I operate it again shortly after, there is no faint click.
 
I have checked that power is reaching the contacts, it appears to be about 24VAC as measured with my multimeter, with one probe on the machine chassis and the other on the contact. I find the TeleType wiring diagrams hard to follow, but I *think* it might need to be 48VAC.
 
Any suggestions what I might look at?
 
Thanks
 
Rob
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