wobble plate switch

[tvtechrich]

Does anyone know if the micro switch attached to the WOBBLE switch is a special ,low force switch ?I replaced my stuck one with a microwave door switch and it seems too stiff for the write in hammer to activate. Thanks 

[jukenorman]

It's not the action of the write-in hammer that activates the wobble switch but the wobble plate solenoid operating.

Norman.

[tvtechrich]

My wobble switch is good now and the solenoid checks out with a power supply. When a selection is made the write motor advances and when the arm finds the pin the light flashes but no power reaches the hammer or wobble solenoid . Having a hard time tracing the current path with the book I have. Do you know? I have checked and burnished the contacts on the write relay and stopping relay .

[jukenorman]

A contact of the stop relay K4-3 dynamically brakes the write-in motor and that must be happening if the lamp is flashing. Another contact of the stop relay K4-2 energises the wobble plate solenoid and accumulator reset coil (which initiates the write-in pulse). So K4-2 would seem to be your problem.

Norman.

[tvtechrich]

Thanks . I'll double check that. Maybe a bad wire I'll do some testing. This is the box that I replaced the 4wire magazine motor with 2 wire motor and just dead ended the unused wire. Motor seems to work and stop just fine, but maybe there was a current path thru the field to the hammers and solenoid ?

[jukenorman]

I did wonder about a two wire motor replacement when you first mentioned it being missing, I think it should be OK. The write-in and read-out circuits are quite separate so shouldn't be causing your write problem.

Norman.

[tvtechrich]

Just to be sure I'm rigging up a circuit to replicate the missing field coil in the motor. Just to see. Thanks for the help .

[tvtechrich]

Well as expected adding a coil did nothing . I found that manually closing the stop relay activates the wobble solenoid and switch, so circuit path is OK. When I select a song the lamp flashes for a millesecond . Seems too short to release the levers. So I added a 1000uf cap across the stop relay coil. Now the lamp,and wobble solenoid stay on for a few seconds and it will write in if the selection is there when the lamp is lit. I though the hammer might be missing the pin, so I aligned it to a5 and it seemed to help . But only if I leave the cap on to stretch the pulse. Plays fine if I push the levers by hand , just won't write. I tensioned and cleaned all the plugs and sockets and they are solid now. I can't see the power supply feeding the hammers , maybe it's low? I thank you for your help .

[jukenorman]

Do you have a service manual? You're at the stage where you need to follow the schem-a-grams from page 28 onwards which explain how the circuits operate and show the "hot" circuits. The lamp flashing is not in the circuit that writes the selection (although it's operated by the stop relay), it dynamically brakes the write-in motor. The stop relay (which also operates the wobble plate solenoid and initiates the write-in) has a self-hold contact K4-1 which holds it energised - is that contact clean?  Or a wiring type issue?

There is quite a bit going on at the point you're having your problem but the stop relay, once it energises, should stay energised until the selection pushbuttons release.  And we know the stop relay must be coming in, otherwise the lamp wouldn't flash.  Definitely K4-1 requires investigation.

Norman.

[tvtechrich]

I have 2 photocopied manuals that were very poorly done. I can't seem to find how to identify the relay contacts . Some of the pictures seem to label K3 as the stop relay, and some K4. Now that I know that it should latch it will help a lot. A pic or drawing showing how the relay contacts are numbered would lelp a lot. Thanks again.

[jukenorman]

K4 is the stop relay, K3 is the write-in relay. You should be able to identify the K4-1 contact reasonably easily, one of the the poles connects directly to ground.

Norman.

[tvtechrich]

I may have found my problem . After reading the nearly illegible text in my book, I saw that it refers to a relay that somehow delays and stretches a pulse to ensure a strong pulse to the hammers .!!! It doesn't go into detail but I noticed an electrolytic capacitor near a relay in the control box. I clipped leads to it and paralleled a large capacitor across it...now all works. With the exception of one B side hammer coil which is defective. I was called away before I could follow up, but I think I may have cracked this nut. More to follow .Thanks again .

[jukenorman]

The fat pulse is for the hammer coils, the wobble plate solenoid is operated directly from the stop relay. I messaged you some (hopefully) better literature!

Norman.

[tvtechrich]

Thanks for all the info. A LOT better than what I was working with . Unfortunately I was able to see that the capacitor I added was in no way related to my problem. Must have been a fluke that it worked 4 times. Today no go. On page 32 sequence 10 it says ''the construction is such that pull in is delayed by 1/20 sec'' But it doesn't say how. If I jimmie the wobble plate so it doesn't pinch the levers so hard, they seem to write properly . It seems the pulse to the wobble plate and hammers is just too weak or short. -21v supply is actually high so it should work. It does sometimes , but not reliably. I've been over the wiring , relay contacts and Wonder if maybe my homemade current limiter bulb is shunting too much dc to the write motor, leaving not enough for the hammers ? I had ordered a#309 but it hasn't arrived yet. It will make me crazy[er] if it fixes it. At least now with the info you sent I can identify all the relays, even if I can't grasp their operation . Thanks again.

[jukenorman]

I think the fact that it has worked four times for you shows it's likely that a fault is present. If when the write-in motor is running, you manually push and hold the stop relay, does it operate the wobble plate solenoid and make a selection? If it does, that would point to the stop relay self-hold contact. I've been thinking about your current limiting lamp - if it makes a selection manually holding the stop relay above, then there should be enough voltage. If it doesn't work manually holding the stop relay, then maybe suspicion is going to fall on the current limiting lamp?

Norman.