Sirius 250 some buttons don´t work anymore

[BSSG]

I´m working now for a long time with my Sirius 250, but last week I switched it on and three buttons were not working anymore: Focus submaster buttons 2 and 10 and brightness submaster button 8.

I changed every single IC on the related circuit board, but problem remains. They just do nothing, LED will also not light up. Switches are working electrically.

Anyone with a good idea?

[iank99]

If you've swapped IC's and checked switches then there's not a lot else on those boards to go wrong, however having just looked at the circuit diagrams - each switch connects to the data lines of the 373's via a diode (probably a small signal diode like 1N4148) mounted alongside the switches. It would be worth prodding the diode's to see if all are being diodes and not gone open circuit.

 

The Led's for those switches are not operated directly by the switch but via another 373 circuit depending on a code from the processor - if the LED isn't lighting then the processor isn't sensing the switch closure, which points back to the switch and it's diode.

[BSSG]

Thanks, I will check the diodes.

Any chance to get the circuit diagram? Would be very helpful.

[iank99]

Send me an eMail to iank'at'centraltheatresupplies.co.uk and I'll send you the ones I have.

[BSSG]

Many thanks, desk is running perfectly again, with the circuit diagram we were able to detect exactly the error, it was one path defective which we replaced by a wire.

[iank99]

That's good news!!! Glad I could help.