Ademco Microtech Galaxy 16+ transformer

[Guest]

You would measure the aux DC voltage at the aux terminals where the detectors are wired in. Looking above though it seems you've already measured this and it seems fine.

Check the voltage either side of the battery fuse with the battery disconnected, should be identical.

[Guest Guest]

You would measure the aux DC voltage at the aux terminals where the detectors are wired in. Looking above though it seems you've already measured this and it seems fine.

Thanks for the clarification, Stuart.

I have just done this anyway and yes, I indeed get the same 13.60 volt where the sensor power leads all join the circuit board as I do at the sensor end of each wire so no dodgy wiring.

Check the voltage either side of the battery fuse with the battery disconnected, should be identical

I'm sorry to be slow on the uptake, but please can you clarify?

I assume from the symptoms when I removed it with the power supply off that the battery fuse is the top one in the bank of three? If so, where should I probe to get the potential difference required?

[Guest]

I assume from the symptoms when I removed it with the power supply off that the battery fuse is the top one in the bank of three?  If so, where should I probe to get the potential difference required?

67543[/snapback]

Yes, the top fuse is the battery fuse. To test the potential ocross the fuse connect the -ve lead on the tester to -ve battery connection on the PCB and the +ve to either side of the fuse. These 2 readings should be the same, i.e. 13.8VDV or thereabouts.

[Guest SjB]

Thanks, Stuart.

Reading from either side of the fuse in the manner you suggest gives 13.65 volt DC.

[Service Engineer]

Reading from either side of the fuse in the manner you suggest gives 13.65 volt DC.

Check to make sure the other fuses are about the same reading.

[Guest SjB]

All six measurement points (three fuses x 2 ends each) give the same reading of 13.65 volt DC *except* for the righthand end of the middle fuse.

This varies between 6.04 volt DC and 13.65 volt DC "at random" as I wiggle my ammeter probe against it.

Have we perhaps found our culprit?

If so, shall I do the obvious next step of removing it, carefully cleaning both the fuse and the fuse holder (despite everything looking clean and uncorroded), and replacing? May be I should try swapping the fuses around and seeing if the problem (varying voltage) moves with the fuse?

Inference from earlier posts is that I can do this with the board 'live'? (I ask because if not, I will also have to reboot my internet router as it is on the same ring circuit!)

Advice appreciated as ever to ensure I don't inadvertently do something that the Galaxy will object to.

TVM!

[Guest]

As long as they are the same rating then it won't do any harm to swap them around just for checking purposes. Sounds like a possible dodgy contact with the lead on the tester but it costs nothing to swap the fuses. It could be a dry joint on the fuse holder, but I think the middle one is the SAB so I would expect the external bell to sound to start up when you remove this one unless it is wired into the aux rather than the hold off. I don't think that this is part of the above problem but you never know!

As for the live\not live thing, technically, the fuses are still 'live' with the battery connected but the mains disconnected. To completely unliven (new word?) the panel would need the mains and battery removing which would start the external sounder sounding. If there is a fused spur next to the panel, (which I think you mentioned there was), then this will sufice to isolate the panel for the purposes of this excercise.

Removing the mains is always a good idea as at worst with a battery only connected to the board you can kill the panel and everything connected to it, with mains present you can do all this and also kill yourself.

[Guest SjB]

More info:

If I press gently on the righthand end of the middle fuse, I see 6.04 volt DC. If I press a little harder I see the same 13.65 volt DC as elsewhere. As soon as I relax the pressure (we are talking about grammes, not kilogrammes!) the reading drops back to 6.04 volt DC.

The righthand end of the battery fuse is now doing the same, in this case varying from 10.70 volt to 13.65 volt depending on how hard I press with the probe.

All other four readings remain rock steady at 13.65 volt.

In neither case am I pressing hard enough to visibly bend the PCB, but could I have a dry solder joint?

[Guest SjB]

Sorry Stuart - we cross posted.

Anyway, I have swapped the "ammeter" probes (i.e plugged the black lead in to the red socket on the "ammeter" and viccy vercky); I still get the same varying readings on the same two fuse contact points even though I am now using the "negative" (black) probe as the positive probe. I don't thereore think the leads are suspect.

In all testing the negative probe has been stuffed in to the open end of the connector on the negative battery lead as it is a nice snug fit.

Thanks for the continued help.

I truly appreciate it.

[Guest SjB]

Trying still to keep an open mind, this is looking more and more like a dodgy connection or dry joint problem...

Since the last post I removed the fuses again and re-inserted them having first squashed each pair of clips together to ensure a tight fit.

A voltage test showed 13.65 volt DC on each side of each fuse, every time, rock steady. Great.

The LED was still flashing though....

An hour passes, and I noticed that the LED on the keypad had stopped flashing.

"Eureka", I thought, so I replaced the control panel lid.

Guess what?

The LED then immediately started flashing again, I guess as a result of vibration from reattaching the lid.

Damn! The odd thing is though that having taken the lid back off, I still have 13.65 volt on each side of each fuse, every time I check so the fuses are now properly seated.