Rowe JAN diplomat selection issue

Hi all, having a selection problem with A rowe JAN. it will start the search unit and sill sometimes select, sometimes not. The select coils will not fire at all. Even when tripping S2 sprag relay. I have cleaned both sides of the circuit board and burnished the wipers. Not sure where to go now . this is the 1st time I have worked on the 1100 mech from this era. Thanks in advance. Mark

This is often a matter of pitted contacts on the relays. However, also check the voltage drop in the power supply. The Low-DC if filtered and when that capacitor loses capacity the ability of the PSU to provide a long enough pulse is eroded. Also, the pin punch length is determined by an electrolytic capacitor. I can't recall if it is on the keyboard assembly ( I believe so), or search unit. That and all electrolytic's should be replaced.

Rob/NYC

Thanks Rob.
I looked at the schematic the cap you mentioned is across points on R1 for the latch coil. that circuit goes from the common to the AC 30v.
the DC checks at 28-30 volts. I can trip the coils directly to the common and they do trip the pins. The a and b coils are hot from the +30 through the keyboard to R1 select pulse relay.
I have not been able to get to the not selecting through the search unit with all keys yet. Mark

Hi all. found problem. it was a hairline crack in the search unit circuit board. it had been repaired before I got it and that repair failed as well as the crack extending into new areas. There was only about 1" of good board left. We got a junker CTI 1 and robbed the part off. works great now! Mark

Hi Mark,
Glad you found it--
Hint: If you ever need to repair a crack in a PC board, again, it's best to drill a small hole at either end of the crack, so it won't expand further. Ron Rich