[Lloyd 1985]

Hi Maarten,

I did a load of tests last night, checked the connection from the H-STAT to the IC, all is well there, also checked the path from the LOPT to the IC too, all seems ok there too, there are some extra components in this monitor that aren’t on that circuit diagram, in fact there’s a whole PCB that’s not on it! It also has connections to IC505 with wires tacked on to the bottom of the PCB, it’s definitely an official Sony mod looking at it.

There are no voltages coming from the H-STAT or LOPT to the IC, but I guess that’s because the line stage is not doing anything, it doesn’t even attempt to start up, so no voltages ever come up from that area. The only way I got it to fun was by injecting my own external 15.625kHz from the function generator, I’ll try it again later and see what voltages come up.

The thing that makes me think the LA7802 is duff is that when I first tried powering the monitor I checked the voltage going into pin 17, one of the VCC pins, and it was something daft like 70V+, I didn’t think much of it at the time, but since getting the service manual I see it’s supposed to be 12.4V, and it shows a zener diode built into it. Now it seems the voltage on pin 17 is only getting to around 8V, and it fluctuates. I’m sure it’s not the resistor feeding it, that measures ok.

Regards
Lloyd