Scantronic 9600 problem

[Masterofnone]

Although an old system, it was working perfectly until the internal alarm started to go off needlessly.  The main alarm panel is in the loft and ever since we've been having some external sub zero temperatures the internal alarm started to trigger and the display on the keypad was showing "Battery Failure". It does get really cold in the loft as everything is insulated so I am wondering if this has anything to do with it? To be on the safe side I replaced the internal battery with a like for like one despite the previous one being changed about 1 1/2 years ago. (Yuasa NP& 12v 7.0AH)

However within a few weeks the same problem arose, whereby the alarm would trigger without it being armed with the same "Battery Failure" indicator on the keypad panel.

 

It may be a common fault but I may be missing something obvious and I would appreciate any help before making the decision to replace the whole system.

 

Many thanks

Edited March 23, 2018 by Masterofnone
Update

[sixwheeledbeast]

It's possible the system is failing and not charging the battery correctly.

You would need to check this with a multimeter, this would normally be done as part of a service and before fitting a new battery.

[Masterofnone]

Thanks for the reply. Any ideas on what component it would be as I wouldn't know what to look for. I was hoping it could be a glass fuse of some kind which would be fairly straightforward for me but can't seem to locate one on the board. 

[sixwheeledbeast]

There are no fuses on the old Scanny boards and it wouldn't be a fuse causing that type of fault.

It's unlikely anyone would repair something down to component level, anyone up to that task would probably have an idea where to start.

Did you check the charging current, system and battery voltages with a meter?

 

[Masterofnone]

Hi, Ive just got myself a multimeter this morning and I`m keen to do some basic checks. I would appreciate some guidance if possible of the best way to check the charging current, system and battery voltage as suggested. Would I be checking the charging current by  unplugging the cable from the motherboard marked 19VAC (purple cable) which is coming in from what I believe to be the transformer. I take it this should show me a voltage of 19V. But Im not sure if thats the system voltage or the charging current though?  This is panning out to be more of a challenge to me now so thank you for all of your help.

[PeterJames]

First off where are you buying your batteries from?  

 

Secondly you say the battery was last changed a couple of years ago how long was it before that?

 

My guess would be that it is the main PCB, lofts are not really the best places for electronic components, they are subject to extreme heat in the summer and cold in the winter all that expanding and contracting doesnt do anything any good. This on top of the fact that the panel is at least fifteen years old and nothing lasts forever especially when you consider that its been on even when its not set, I would be happy if I had got that life expectancy out of a fridge .

 

You could try breaking down the circuit board to component level to try and work out which bridge rectifier or transistor is failing, but its unlikely you will get help with that here, the time it takes to diagnose a fault to component level versus the cost to replace the cpu is far outweighed, so most engineers only know how to replace panels. The other problem is you really need an oscilloscope and the knowledge on how to use it a multimeter will only tell you the basics  

[MrHappy]

2 hours ago, Masterofnone said:

But Im not sure if thats the system voltage or the charging current though?

 

 

ac voltage comes onto the board & charged to dc volatge to run the system

 

a 9600 came out in late 80's so could be upto 30yrs old, unless its a duff battery or the system is overloaded its probably the  pcb on its way out

Edited March 24, 2018 by MrHappy

[sixwheeledbeast]

Voltage checks would be done parallel to the circuit and current checks would be done in series with the circuit.

You MUST have your meter leads plugged in the correct ports for both tests or you will blow either the meter or the panel.

 

The 19Vac is the transformer voltage to the control panel not the system voltage which should be a stable DC voltage measured from the control panel.

You may simply have bought a cheap battery and it's failed however, panels that consume batteries quickly normally have a problem.

 

A simple step would be to have your meter on DC Voltage (red lead in V), and test in parallel (so Red-Red, Blk-Blk) the voltage across the battery leads with and without the battery.

If the above makes no sense or you don't feel competent, its time to call in an engineer. There are mains voltages in there remember.

 

FWIW I wouldn't expect to use a scope to diagnose that kind of component fault.

If its a component it would likely be in the power supply circuit, so maybe voltage regulator most likely an LM317. Even if replaced the rest of the components are of a similar age so not worth the effort IMO.

[Masterofnone]

The battery was changed 1/1/2 years ago and prior to that 7 years ago. The new battery was a like for like (Yuasa NP& 12v 7.0AH) and was purchased from a reputable alarm company. Admittedly this system has served me well over the years so I just want to carry out some basic checks to eliminate anything really simple or obvious before replacing the system. I appreciate all the help and I know It would be much simpler to replace a new system back into the loft as all the cables are already there but I never took into consideration the detrimental impact that a loft could have until it was just mentioned in this forum so thank you for that. I really dont want at this stage to have to lift  carpets and floorboards up as everything's been decorated and re carpeted recently.

The checks I have carried out thus far are as follows:

There is 18v AC coming out of the transformer and going into the circuit board. There is 13.82v DC coming out from the leads going to the battery with the battery taken out. The battery disconnected is showing 13.7v DC. With the battery connected its showing 13.82vDC.

Many thanks

[sixwheeledbeast]

With the leads in the same position and battery connected switch the mains off, monitor for 15 minutes or more and then the same with the mains back on.

The float charge will drop quickly then voltage will drop slowly. When the mains is reapplied it should increase steady to the value of your initial readings in a similar amount of time.

Not an accurate current reading but will show if the panel is charging the battery

 

As for a replacement and your cabling, an expander module could be used in the loft and the controls moved or alternatively wireless or hybrid somehow.

Lots of options and solutions available.