by Rob-NYC »
Mon Dec 08, 2014 7:38 pm
I'm surprised no one chimed-in on this one.
So, basic troubleshoot:
When two buttons are pressed, does the search unit ever stop and do you see any sprag relay action? If so, check-clean contacts in the search relays and replace caps (do these anyway).
If the search unit just spins and never stops, it means that either the chase wipers in the search unit are worn (common) or there is a break in connection to, or in the keyboard letter-number series contacts.
If two buttons are pressed the search unit should rotate for a second or-so and when the wipers hit the hot segments the sprag relay to the right pulls down. This does three things:
1) Cuts power to the search motor.
2) Stops the hammers over the correct pin.
3) Applies the write-in pulse.
All of the above are centered on the condition of the contacts on the various relays. The length of the pulse is determined by a electrolytic capacitor of approx 100mfd and any caps in the search unit are due for replacement.
I recommend a service manual, but the main area of danger to the machine is the amplifier and failing capacitors. That needs to be dealt with if it hasn't been done in at least the last 20 years.
Rob/NYC
"If we believe absurdities, we shall commit atrocities" -- Voltaire