Friday, 12 June 2015

Follow up to Marmitek/Haibrain SC9000 PSU failure

This is a bit of a follow up to my previous post on the Haibrain SC9000 X10 alarm unit that I use at home. I decided to bite the bullet and purchase a replacement power supply (£15 so not cheap, but then again not too pricey) and it arrived a few days later. I've finally got round to fitting it and as I did made a few observations and notes for the future.

I took quite a few photos which are all in this post, so apologies for it being graphically heavy.

Firstly, the new unit arrived, and unboxing showed it to be identical to the original, no change to voltage, current, etc. So first thing I did was connected it up as a test and checked, yep the alarm would now sound and all the X10 commands started to flow, so it appears this IS a faulty power supply that causes the alarm sounder not to trigger and the X10 commands to fail. At least I'd now determined the root cause of the fault, it wasn't the overall alarm unit.
Next, I wanted to try and see WHY the original failed and if possible make the new one last longer. One thing I'd always noted was that it ran hot, as most step-down transformers give off heat this isn't unusual, but they generally have vents or at least some way of expelling the heat. This one doesn't, the power supply is a sealed black brick, no vents or anything and when I say it ran hot, you wouldn't want to hold it in the palm of your hand long, it's that sort of heat. So my thinking is I give it some vents before I put the new one into service to help loose the heat, my thinking is most electronics prefer to run cool than hot and it might stop the failure occurring again.
This meant my favourite (ha ha) thing of all time, take something brand new that I've just paid for, take it apart and modify it! But luckily these PSUs have 4 clear screws and a simple case, so taking it apart isn't a challenge. Once opened up, split the two halves of the case carefully as one circuit board stays in one side, the other in the base as you can see from this photo with the case carefully separated:

The right is the "base" which has the main transformer and a circuit board that covers the base, along with at the top right the 2-pin mains in socket.
The left "top" holds a much smaller IC-containing board and the output wire that feeds to the alarm (4-wire). The small circuit board has a single screw in it (just visible on photo, bottom left) so take that out and the top casing comes completely clear. This was ideal, my thinking was to make air vents right along where that bulky transformer sat as that's where the heat was generated, and it was VERY snug alongside other electronics, so a good bet.
I set about the case with my dremel, and here I show my failure as a practical/mechanical/precision person, the air holes are horrible, not neat, but I sanded them down so no rough edges and I think they'll do the job.
 
As you can see they aren't neat, but should allow a bit of heat to escape. Putting it all back together and it looks like the vents are in the right place, right over the transformer.

Now since I fitted the front of the SC9000 to a wall, and then fitted the cable into the gap between the plaster and wall (inside the wall), the next problem was re-feeding the wire to the right place. So I decided not to, and to simply cut the cables and join them back up using a connector block. That way I didn't have to re-trace the cabling in the wall and make life a lot easier!
As you can see, I was feeling quite neat today and even used a connector block (instead of twisting the wires together and taping them together). I then wrapped the block in tape so it was secure and no potential for shorts or anything getting in there.

Putting it all back together, power on and it all worked fine!
(Note for later, when the batteries are low, the green battery light stays on! I thought the power supply had blown somewhere in the process as the green light stayed on. Seems the green light not only shows it's running on batteries, but also that the batteries are low!)

Next, I decided to properly pull apart the old supply, as I'd like to find what failed and possibly fix it, so in future I have a way of repairing these things with just a few parts.
Below are a load of photos of the teardown, I've not yet had time to investigate all the parts but will do very shortly and probably try a trial and error of replacing parts until I discover the failed unit. However as you'll see there are quite a few scorch marks on components, so I'll be starting work there, which is also where I believe the mains part of the circuit resides, hence this bit will be more susceptible to mains spikes, etc, (which is what Marmitek/Haibrain state as the issue when the PSU fails, it's a mains spike)

The main split board from above

The smaller IC board

The top corner of the main board, no obvious damage here.

 After removing the transformer, some scorching of the main board was clear, I'm now suspecting this is where the issue is.


 Underneath shows more heat damage.


 Closer view of the high voltage components that sit almost exactly underneath the transformer.





After inspection I suspect looking at these components closely, however they are only a couple of resistors, so I'm not hopeful that it would be something as simple as these failing!

3 comments:

  1. Hello Andy.
    I did fix my power supply. From memory : main culprit was 2SC667 which had a short, there was a S9014 which was also bad (although it did not show as shorted on the multimeter, but the resistance was not ok) and the 5-6 winding on the transformer connected to the smaller yellow capacitor (i think it was the 0.22uF) was open. I'm sorry i cannot give you the exact silkscreen numbers, but it's easy to figure out :)

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  2. Thx! Andy for the info on the PSU. Mines acting up lately (after 7 yrs) with the same symptoms. At least I know what causes that after I read your post.
    Just to share with you in case you plan to squeeze more juices out of your SC9000. While u can remotely arm/disarm your SC9000 using telephone, U can also use Broadlink RM Pro to arm/disarm via wifi/internet. It seems that Broadlink uses 433.92 therefore I think their motion sensor and contact sensor can be used with SC9000. I have RM Pro and will look into S1 soon. What I like abt SC9000 is it still uses the old school telephone dial out.

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  3. Hello Andy, thanks for the effort to inform others about this badly designed power supply and transmitter.
    At last I also managed to repair my PSU. I firstly got inspired by Ted and his solution, but my components were OK. Then, after a few weeks not working with this PSU, I started to suspect the electrolytic capacitors. The main problem with the PSU is that it gets very hot because of the small box and no ventilation holes and these type of capacitors dries out by heat. And I also started to suspect them because my alarm central started to more often have problems transmitting on/off commands to power line controlled plugin modules. It didn’t happen suddenly but slowly got worse and then failed completely, and this behavior could be caused by these capacitors.
    And it was! I replaced the big one 220uF/50V and the small one 10uF/50V and the PSU was working like new! These capacitors are seen in the fourth picture counted from below and are positioned directly to the left of the smallest yellow rectangular capacitor. They are round, black, and with the white stripe indicating negative wire.
    I must admit, I should have checked these capacitors absolutely first and so should YOU!
    (you get cheap component testers on www.ebay.com from Asia)
    To make these PSU’s last longer I also do this:
    In the last picture, almost in centre, you see what seems to be two resistors (one green and one brown). The green one is actually an inductor and they make part of a filter. They get very hot and to get more cooling air around them I solder longer leads on the legs (taken from other new resistors or like that) and position them so no short circuit will occur.
    And the last thing to do is NOT assemble all of it back into the original box, but rather let all of it be disassembled and placed in a bigger box. I use a plastic box with som drilled holes in both ends at the top and I place a thin plate of wood in the bottom of the box to withstand the heat coming from the circuit board (still heated by some rectifier diodes).
    Best regards,
    Helge

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