[frsimen]

Hello Mark,

Thank you for the measured results. I was working from a less than perfectly clear printout of the circuit diagram last night and missed another path which will need to be disconnected. As well as the wires on terminals 9 and 10, the wire on terminal 8 on the phase detector board needs to be disconnected. There should then be 0V on pin 2 of IC15 on the logic board.

The voltage you have measured on terminal 9 on the phase detector board could be coming via R29 and terminal 4 and should disappear if the wire to terminal 4 is disconnected. There should then be 0V on terminal 8 too.

The voltage on terminal 10 is a mystery as there is no obvious path for anything there. R32 should pull the line low, so there must be a significant amount of leakage for you to measure 6V. However, 6.07v is suspiciously close to half of 12.17v that you measure on terminal 9. I think there is a short circuit between possibly terminal 11 and terminal 10 or terminal 8 and terminal 10. Terminals 8 and 11 should have 12V on them if terminal 9 has. If one of them measures 6V, there is a short circuit somewhere in the area between that terminal and terminal 10. Careful inspection of the terminals and the PCB tracks should reveal the cause.

The 10 ohm resistor makes no sense at all. Terminal 9 on the logic board is the +12V supply. The circuit shows R 63 10 ohm resistor and C30 a 47µF capacitor, but neither are connected to pin 13. Pin 13 is the up down tuning line. It’s clear from the photo that the resistor connects to pin 13 at one end but that is not in agreement with the circuit and I can’t understand what is going on here at all. The capacitor is a recent addition by the look of it.

I wouldn’t worry about the fine tuning problem for the moment, that’s a battle for later! Leave that control in the SLOW position, then it won’t cause any trouble for the present.
The TC1 line voltage (terminal 28 on the logic board) should be 12V in the fast and slow positions, but should drop to more like 2V in the hold position.
The TC2 line voltage (terminal 24 on the logic board) should be 12V in the slow and hold position and ought to drop to 0V in the fast position.

There seems to be quite a lot that isn’t right at the moment, the resistor connected to terminal 13 on the logic board is certainly a puzzle. Can you check for continuity on the logic board between TP8 and terminal 13. The circuit shows that they are connected. I wonder if they are on your PCB. If they are, that resistor really should not be connected to pin 13.

Paula