Can you diagnose the fault?

[joe-90]

I've got an alarm to fix about an hours drive away so I want to sort it first go.

The info I have is:

Panel Scantronic 9452.

Gardtec Siren unit.

Customer came home and found zone 1 lit but alarm had no entry tone.

He pressed a few keys but had no sound from keypad, and keys had no effect.

PIRs still operated as normal.

What is the fault?

I think it's one I only get about once a decade. Any ideas? Anyone want to guess?

 

[breezer]

as its scantronic down power and repower it

may be lightning strike / power surge (unlikely)

battery on its way out (possible)

speaker blown up so he cant hear any noise (very unlikely)

 

[joe-90]

I haven't been out there yet, but it sounds like a fault I've had in the past.

The toroidal transformer in the strobe assembly goes short circuit and blows the fuse in the panel when it tries to flash. It is the same fuse that powers the keypad bleeper - hence no sound.

If I replace the fuse, then all will seem well until the next time the strobe tries to flash - then the whole thing repeats.

I've had this fault just twice in 20 years.

Will find out next week.

 

[breezer]

your diagnosis does not sound right to me, the strobe is powered by the aux(ilary) fuse or is it the bell fuse? either way none power the keypad. since if what you say is true why is it showing cct1 lit?

 

[securespark]

I'm with breezer - I reckon it's a spike or surge, locking out the RKP.

Not familiar with Scantronic but if they have NVM, reset it & possibly replace a fuse & I reckon you might be OK.

The ADE's I used to reset after lightning strikes had all manner of LED's showing- no rhyme or reason to it.

 

[joe-90]

It's a fault I've had before. It shows 'circuit one' as that is the zone that gave a false alarm. The alarm operated up until that point but when the strobe tried to flash - it goes short circuit. It's not a power surge.

 

[breezer]

.......... it goes short circuit. It's not a power surge.

so what happens in a short circuit then?

 

[joe-90]

.......... it goes short circuit. It's not a power surge.

so what happens in a short circuit then?

Are you saying you've never had one?

 

[breezer]

i am saying what is a short cct if its not a surge (until the fuse blows)

never seen such as you descibe though

 

[joe-90]

It's not a surge at all! A surge is a sudden inflow of power that is greater than the power of the system. It's a mains born phenomena. When a substation fires up there is often a surge that is far higher than the usual voltage - hence damage to the system.
A short circuit is when you have , for example 12v + going to 12v - .

 

[breezer]

yes i realise that, but i also realise i didnt say it as imeant.

it is a surge as far as the pcb is concenred, the detectors etc run on 12v, but the electronics dont, so to the electronics it is a surge

 

[bernardgreen]

the detectors etc run on 12v, but the electronics dont, so to the electronics it is a surge

It's an overvolt.........