Honeywell Accenta fault

[greenhouse24]

I am trying to diagnose a fault on a Honeywell Accenta alarm that's used in a church. A while back the external sounders started going off, although the alarm itself wasn't triggered. The alarm itself and the keypad seem to work fine, it's simply the external sounder that is continually going off.

Disconnecting the D and B terminals on the main PCB stop the external sounders (presumably since there's no 12v running to it any more) and the rest of the alarm system continues to work fine.

Poking the TADB terminals on the alarm (while not alarming) with a multimeter shows:
A to D 11.68V
A to B 300mV but occasionally jumps to 3V
A to T 0V
A to Strobe 600mV

If the alarm is triggered, there is no difference in the A to B reading, it's still 300mV with occasional jumps.

I would expect the B terminal to be high when there's no alarm and low in the alarm condition, unless I'm misunderstanding how it works.

Any ideas what might be wrong, or is the PCB just fried and needs replacing.

 

[sparkymarka]

Probably it’s lost 12v +….or tamper switch issue and the bell tamper in the panel is linked out ….also check battery charging resistor as they can burn out with a faulty battery ….post pictures of pcb..

 

[greenhouse24]

Thanks for the reply.

I'm fairly confident it's not tamper, as when the external sounder is disconnected the system all works correctly - ie the internal sounder goes off if I open the case and the spring-loaded button is no longer depressed.

I'll grab some photos of the PCB next time I'm in the building.

 

[sparkymarka]

ok post pictures