the LCD is only properly compatible with the GEN4 series of Accentas. it will work but if you have an open zone you aint going to know apart from it not arming.
swap the old LED back and see what happens, if you have an open zone it will tell you which one?
if the outside siren went off when you powered down then you will need to disable the battery connection inside the bell first.
there will be screws to open it up.
if it didnt go off then you should be ok to disconnect at any point. dont go clipping any cables as you may well need them for...
Hi did you try the topics at the bottom of your page. its typical on here that your going to get unhelpful advice with an old alarm system. you could pick up a honeywell GEN4 panel to replace it or follow the link advice. where are you in hampshire?
Ok its a AJ600 and very old probably one of the last ones manufactured as there is no resistor on the speaker.
if you did the power down and the speaker fuse is ok and still nothing then maybe time for a new panel.
google/ebay Honeywell optima gen4 its probably the closest in size and...
as above then you need to power the system down and reboot it.
another note are the buttons rubberised or flat like a membrane.
if they are rubberised then you have an AJ600N which needs a NVM reset.
post a picture of the panel.
If you put your code in or the factory code do any LEDs change ie tamper or panic.
if they do then the speaker fuse has blown or the resistor connected to the speaker has become detached, probably due to a power cut.(the resistor can be resoldered back on again)
if the LEDs dont change then...
4 months is not a long time. do your leds flash when you walk past a sensor, if yes then you have to move the walk test switch which disables the led thus saving battery life.