Wonder if any one can assist me please. I have an alarm that was professionally installed and maintained for a couple of years. After which, we allowed the maintenance contract to expire. As an electronics engineer myself, I have changed the battery every couple of years, but now the alarm (based upon an Optima XM6 circuit board) has developed a fault. The high level internal sounder will not work when the battery is disconnected, neither will the external sounder/bell. When the battery is connected then the high level sounder will not test, but works when the alarm is set then triggered. The external sounder and strobe will not test nor work when the alarm is set then activated. The battery trickle charge (off load) voltage is only 9.5V. Both fuses are intact. I think that the battery is obviously supplying 12V to the high level sounder and the board is not, neither is it supplying the external bell unit and strobe, or (as is more likely) the external sounder unit is faulty. I suspect that a component within the AC bridge rectifier circuitry that supplies the trickle charge to the battery and the internal high level sounder has gone, but without a PCB circuit diagram, I cannot hope to sort it out. There is no obvious signs of overheating anywhere on the board and the alarm works 100% (high level internal sounder) when set and triggered by any of the five PIRs attached. But obviously - the battery is suppling the 12V for the high level internal sounder to function. All logic circuitry on the PCB is functioning as it should and has it's own 12V supply from (obviously) another AC bridge rectifier on the PCB.

Check for dry joints and hairline crack to the pcb print around the charger circuit. Then check the zeners and regulator and the electrolytic. The components on the trickle charge section run very hot and can stress the pcb. This is a simple part of the circuit.

I suspect that a component within the AC bridge rectifier circuitry that supplies the trickle charge to the battery and the internal high level sounder has gone, but without a PCB circuit diagram, I cannot hope to sort it out.

20vac onto the board

Four diodes, a resistor, capacitor, a resistor or two & a couple of voltage regulators bolted to the keypad chassis

I think you should be able to eyeball that no worries

The simple thing is remove all items powered by the board inc battery, if it ain't given out 13-16 volts dc, bin it

20vac onto the board

Four diodes, a resistor, capacitor, a resistor or two & a couple of voltage regulators bolted to the keypad chassis

I think you should be able to eyeball that no worries

The simple thing is remove all items powered by the board inc battery, if it ain't given out 13-16 volts dc, bin it