I've recently been doing some redecoration which necessitated the
removal of a PIR.
When I put it back I seemed to have damaged it somehow.
The alarm panel is now showing a constant tamper fault light which I
can't deactivate.

Usually just removing and replacing the cover does the trick but this
time it's with no effect.
I don't know how the tamper sensor works so can't work out what else
to try with the PIR itself.

The system is, quite an old, Scantronic 4700 system with wireless
PIRs.

I don't have the engineer code for this box only the general activate/
deactivate code.

Can I replace the PIR using something generic? I'd rather not have to
replace the entire system as this one does the job very well normally.

Any alarm techies here who can advise?


Ham

In article ,
phantomzone writes:
I've recently been doing some redecoration which necessitated the
removal of a PIR.
When I put it back I seemed to have damaged it somehow.
The alarm panel is now showing a constant tamper fault light which I
can't deactivate.

Usually just removing and replacing the cover does the trick but this
time it's with no effect.
I don't know how the tamper sensor works so can't work out what else
to try with the PIR itself.

In most (particularly cheap, home) PIRs, it's nothing more than
a mechanical contact, e.g. a microswitch, piece of bent metal,
or a spring pressing on a PCB mounted minature push button
mechanisn.

In some more expensive PIRs, it's a signal generated by the
microcontroller. It will operate if the unit loses power
(probably not in the case of a wireless sensor) or if the
microcontroller detects a fault in the unit.

The system is, quite an old, Scantronic 4700 system with wireless
PIRs.

I don't have the engineer code for this box only the general activate/
deactivate code.

Some panels will require (or can be programmed to require) the
engineer code after a tamper fault even if the fault is cleared.
Sounds like you know from past experience that isn't the case
with yours though?

Can I replace the PIR using something generic? I'd rather not have to
replace the entire system as this one does the job very well normally.

Wired ones, yes. Wireless tends to require the exact same part,
which are usually no longer available by the time one breaks :-(.
However, I don't know about your Scantronic.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On 09 Aug 2008 17:42:18 GMT, (Andrew Gabriel) wrote:

In article ,
phantomzone writes:
I've recently been doing some redecoration which necessitated the
removal of a PIR.
When I put it back I seemed to have damaged it somehow.
The alarm panel is now showing a constant tamper fault light which I
can't deactivate.

Usually just removing and replacing the cover does the trick but this
time it's with no effect.
I don't know how the tamper sensor works so can't work out what else
to try with the PIR itself.

In most (particularly cheap, home) PIRs, it's nothing more than
a mechanical contact, e.g. a microswitch, piece of bent metal,
or a spring pressing on a PCB mounted minature push button
mechanisn.

One common mechanism is a spring fitted to a pcb-mounted pushbutton -maybe this fell off...
The tamper switch will be a mechanical switch of some sort - have a good look and you should be
able to find it, and then you may see why it isn't working when the lid is replaced.

Hi
Scantronics systems are still amongst the most reliable and Cooper Menvier
who now are Scantronics have a very good archive.
However the 4700 series is no longer with us being superseded by the 500r
and now even that is out of date.
The 4705 pir you refer to IIR has both rear and front tampers and was prone
to a rear tamper fault if the cover was hit causing it to fall off.
Remove the pcb and hold it in your hand pressing both the front and rear
tamper micro-switches then try resetting the panel.
When testing the 4705 PIR detector you must remember that the detector will
go to sleep after an activation for about three minutes to conserve battery
power.

If you have the engineers code you can put the panel in walk test instead.
I have a PDF of the manual should you need it to help in your struggle.
HTH
CJ

Hi, firstly thanks to all of you for your input it is as always
greatly appreciated.

I found the microswitch. Once I pushed it down I can hear a definite
click which removes the fault from the panel and leaves the tamper
light on.
When I put the cover back on the fault light re-appears thus
preventing me from clearing the tamper light.

I looked on the other working PIRs and I dont see what keeps the
tamper switch depressed. i.e. when the cover is lifted it would raise
and then show tamper.
So I cant seem to work out how that switch is actually activating.

Andrew- In the past when i replaced the battery on the PIR it would
show tamper and then I would just need to put in the user code and it
would clear. So in that case it didnt need an engineer code.

CJ - I couldnt see a rear tamper (I removed the whole PCB from the
casing to look at the back. On the front part of the PCB it has a 4700
sticker so I assume that maybe the 4700 and 4705 PIRs differ in this
respect.

I've put some pics here
http://www.flickr.com/gp/71954231@N00/i61g8V
if you have any further suggestions...

....although I'm getting the feeling that the new TV will have to wait
a bit longer until a new alarm is fitted

Hi
The tamper switch is the small micro-switch on the corner of the PCB.
It is activated by a plastic rib on the inside of the lens cover a common
fault with all Scantronics pir's is that if the sensor is not exactly flat
to the wall the switch will not make.
A very easy fix is to carefully bend the switch arm .
To do this hold the switch closed with one finger and gently bend the arm
away from the switch making sure the bend is between the actuator pin and
the free end.
(IE The steel strip is fixed to the switch body at one end it then passes
over a raised actuator pin about 1/4 of the way down the switch length
before continuing for the length of the switch.).
Also check that the cover fits snugly they should locate with a click .
HTH
CJ