Nexus 8 Home Alarm system

[Toonfan#1]

Hi after some advice regarding a Nexus 8 alarm system, the transformer inside the main panel has failed and the alarm will now only work from the battery, obviously not ideal.
I have contacted Lynteck about a replacement transformer and they tell me that the product is discontinued and I should replace the whole system, seems a bit serious and costly.

Anyone got any ideas on how I can change the transformer or repair it?

thanks in advance

 

[sparkymarka]

Post picture of transformer inc size and voltage ....

 

[mattylad]

Does the transformer have a voltage label on it at all?
The primary will be 240v, but we'd need to know what the secondary (output) is in volts and amps/va

Can you post a close up/good quality photo of the panel and transformer especially?
I'm struggling to find an image online but can find plenty of transformers on ebay.
Then we can find you a replacement.

(although we can probably find one by assuming it needs somewhere around 17-18v as ISTR there is a rectifier on the pcb.

The engineers manual:
https://thesecuritybunker.co.uk/manuals/Nexus 8 Engineer Manual.pdf

 

[sparkymarka]

Think your going to struggle with that one ....looking at the manual above it’s an integral psu board like the old pyronix paragons ! Have you checked the onboard fuse on the psu pcb ?

 

[sparkymarka]

 

[mattylad]

AHA! that reminds me (I used to work in the Nelson factory where they were made).

While I know the guy that designed it, I cannot remember the internals of the inside of the nexus - the PSU and the main board are seperate items, not too sure exactly how they are joined together?

This may fit:
https://www.ebay.co.uk/itm/Scantron...972599?hash=item56d7ef5077:g:IssAAOSwfsReMYey

Else fitting this in and wiring it to the pads on the PCB could get work:
https://www.ebay.co.uk/itm/Honeywel...972562?hash=item56d7ef5052:g:QNYAAOSwuJFeMYG9

Or search for an external PSU?

 

[sparkymarka]

Probably not the transformer but some other components on that board , even a dry joint as it’s very rare for the transformer to go faulty ....probably changed about 6 transformers in 30years

 

[Toonfan#1]

Thanks for the posts, I have attached some photos of the transformer, board, I have checked all fuses and they are ok and as for voltage for secondary I don’t know but the guys from Lynteck did send me the engineers manual, this has some details on voltage etc.

 

[sparkymarka]

Do you have a multimeter ?

 

[mattylad]

Take note of where the wires go.
Turn off the power to the alarm, either at the Consumer Unit or nearby Isolator etc. (whatever it is thats supplying power).
Disconnect the PSU board, unscrew it from the backbox and inspect all the joints.
I know that the PCB will be soldered with lead free soldering and likely to a dry joint after this time, this may be the only problem.
Google "how identify dry joint" and click on "images" to see how to identify this.

If you see anything that looks like the photos in the search results then a simple bit of re soldering may fix the problem.
Question is, do you have a soldering iron or a multimeter and the ability to use them?

 

[Toonfan#1]

Yes I have a multimeter, and the unit has a small amount of staining / burning on the back.

 

[Toonfan#1]

I have also noticed some slight burning marks around the resistor on the other side

 

[Toonfan#1]

Opposite side

 

[sparkymarka]

That to me looks like a bridge rectifier that is dry jointed for a start ! on all 4 pins

 

[sparkymarka]