Wurlitzer OMT - K and Z LED dark on SCC

Hello,

I'm having an issue with my OMT where the carousel spins endlessly after making a selection.
The index light is present and working, but the K and Z indicators on the SCC are dark. I have replaced all the fuses.

Any idea what the problem could be?

Thanks,
Dan

Hi Dan!

Check the plug for the light gates at the SCC. If it was put in at wrong polarity, both inputs for "Z" and "K" would be shorted to ground and prevent the gates from working.

If that is not the case, check IC4 and its surrounding circuitry.


-Catboy

Than you! That was precisely the problem, the cable was put in backwards. Now I have a new problem with the gripper arm.

Initially on power up after replacing the fuses the gripper motor ran to return the arm back to the carousel, but it has not moved again. As according to the manual I have tried placing a jumper cable between the blue and green poles:[imgur.com] , but the motor did not run. If I have done this correctly, this leads me to believe there is a problem with the relay?

When bridging the blue and the green wire on the "blue" plug doesn't have any effect, please check fuse Si4 (fuses +30V) again and - of course - make sure the SERVICE switch next to the gripper arm is correctly set to ON.


-Catboy

I'm not sure what I did differently but the motor is now working when bridging the blue and green wires.

However, it still doesn't work in service mode when holding '9', which leads me to believe it's a problem with the SCC as described in the manual.

Here are some pics of my SCC:
[imgur.com]
[imgur.com]

Is there anything obvious that I should check? I'm wondering if the relay has failed. I might be going beyond my depths of knowledge in servicing the SCC, so if necessary I will have to have an expert look over it.

When you push key "9" in service mode, does relay "M" actuate?
If so, remove the transparent plastic cap from the relay and check if the contact blades reliably touch each other when the relay is activated. Clean and adjust the blades if necessary.

If it doesn't click/react at all, you'll probably have to troubleshoot the relay itself or its driver transistor.


-Catboy

The relay doesn't activate, it stays quiet.

Do you know where I can find a circuit diagram for this computer?

Thanks for your help Kai!

Schematics can be found in the manual.

If you don't own it, you can order one here in the shop.

However, to get you started, check resistor R47 and transistor T2.
Temporarily bridging the outer pins of T2 (collector and emitter) should activate the relay.
If not - check relay M and its protection diode D11.

If it does, check if there is an input signal at the base of T2 when the relay should actuate.
If there is - replace T2.
If there isn't - check connection between resistor R47 and pin 15 of IC8 and between R47 and the base of T2 as there might be a break somewhere.

I hope this helps.


-Catboy