Possible repair of 5508D1AP (8 Channel Dimmer) (no C-Bus Power included)

Hi All

A while back I had an 8 Channel Dimmer unit without C-Bus power supply (5508D1AP) die on me and have since replaced it. I still have the dead unit and decided this week to tinker a bit and see if I can't get it working again to keep as emergency spare. I managed to open the unit carefully and since the unit did not power up I started with the PCB to the left of the unit where the incoming mains power is connected. After some investigation I found a small capacitor on the bottom of this PCB which is showing a short and also the one primary winding on the Thai Lin transformer showing an open loop. Probably damaged due to the shorted capacitor. Attached are some photos for clarity as well as a rudimentary partial schematic of this PCB's circuits continuity traced. It might not be completely accurate but hopefully gives an idea. I then proceeded to remove the shorted capacitor (unfortunately it broke during removal) and replaced it with an arbitrary ceramic capacitor soldered in place. Obviously not the same capacitance but seeing as the original broke I couldn't establish capacitance and took the gamble that this capacitor only acts as high frequency filter and should hopefully not be a make-or-break component for power up. Also had another transformer with similar rating to use as replacement but the footprint and dimensions are different so it can't be soldered in place and it is temporarily connected with wires soldered to PCB pin locations accordingly. I was doubtful it would work but when I carefully connected mains power (obviously an electrocution risk with open 230Vac) the unit miraculously powered up and seems to be working. C-bus functioning however not confirmed. So now I have a few questions I am hoping the experts on here can assist with:

• I am in South-Africa and can't seem to find a supplier for this specific transformer nor a transformer with the same dimensions and footprint. Do any of your know where I can source a replacement?
• Do any of you know the capacitance of the ceramic capacitor in question and does correct capacitance play a critical role when it comes to the C-bus clock and communications downstream in the circuitry?
• I only have this dimmer unit available without C-bus power supply for testing and would prefer not to remove dimmer, relay or PC interface units from the premises where the system is installed and running smoothly.
  
  • What is the minimum most cost effective way of getting a mini functional C-bus testing station up and running?
    
  • If I buy a used 5500PS C-bus power supply will it provide a C-bus clock signal too or if not will it be sufficient to software select a built-in network clock on the Dimmer Unit if one is present?
  • Which leads to the last question can a C-Bus toolkit on PC connection somehow be made without a PC Interface (5500PCU) or is this the only way?

Any help greatly appreciated!

 

I can only help with the CBus power supply question. You can’t see the power supply in toolkit on the network. Therefore you can’t set a burden/clock on it. You can only create it in the database to calculate the current supplied to the network.

As far as setting the clock on this unit goes. I can confirm that in my own 8 channel dimmer without a power supply this is an option.

My understanding is that you can only connect to the network with a serial/USB PC interface, telephone interface(Serial) or Ethernet interface.

The other questions will be best left to those much smarter than me.

Cheers, best of luck, and thanks for the circuit theory lesson (a trip down amnesia lane)

Jason

 

I did some digging as the kids are out...

You probably already saw this link from their website.

https://www.thailin.com.hk/?page_id=1321

it still looks they make that model transformer. Perhaps drop them an email and they may send you a couple for a few rand each. In my experience companies like this sometimes ship anything anywhere.

Also RS Electronics have this model (different manufacturer) that has the same specs 2x115V in 2x 12V out and 6VA rating. It looks like a few of the pins may be a few mm out, but if there are no tracks underneath or an earth plane embedded in the board, you may be able to drill through the board and use a small jumper wire from those pins to the solder pads. The transformer would still be held in by the pins that are directly soldered. They want AU15.42 for them.

https://au.rs-online.com/web/p/pcb-transformers/1213841/

As far as the rectifier goes, if you need one as well, I picked up a DB104 from our local electronics supplier (Jaycar in sydney). It's probably compatible. Datasheet below if you also needed one. It's a DIL package and you just bend the pins out and cut them short for surface mount. I used it to fix a low voltage (12V) hot water controller that had a non polar connection method.

https://www.jaycar.com.au/dil-1a-400v-bridge-rectifier/p/ZR1308

It was AU$1.25!

Cheers

Jason

 

HI Jason

Thank you so much for your posts.

So if my understanding is correct to get a testing station up and running I would need a 5500PS power supply and one of these, "serial/USB PC interface, telephone interface(Serial) or Ethernet interface". I will look for some good deals on e-bay, if any of you have old units lying around you are willing to sell please let me know.

I did indeed contact Thai Lin as per your link but have not received a response. It might be a case of them only selling in bulk or perhaps since I'm far removed in South-Africa it is not worth the effort for them under current global logistical conditions with covid-19. I know it might be asking too much but any chance you can source 2 or 3 from your side in Australia and forward to me? I would obviously pay a handling fee

Coincidentally, before I found this other transformer, I already ordered the exact one as per your post from RS Electronics locally for testing. It has however not been delivered yet and I would prefer not to drill and fiddle with the PCB too much. It might become quite a "dirty" repair so first prize is definitely still the Thai Lin transformer... plus I think it has better safety ratings/fail-safe protections.

Luckily the rectifier still seems to be working ok, so no need for replacement there.

Thanks again!

Tom

 

Hi Tom,

glad to have been of some help.

You are correct. Minimum setup is interface and power supply plus your device under test/configuration. Wire up your power supply SAFELY with an appliance lead (earthed) and mount it above your workbench. You can even make a portable version in a hard case.

Quite frequently there are serial/USB PC interfaces on ebay at an ok price. As Clipsal was originally Australian, make sure you include items for sale on ebay in Australia in your search criteria. Given laptops rarely have serial ports anymore, a USB one would be your best bet, however let price be your guide. If the serial port ones are substantially cheaper then go for one of them and get a serial-USB cable. You can get an Ethernet interface (5500CN2) with a crossover cable To your laptop/PC if you don’t have a Ethernet switch handy. The Ethernet interfaces are more expensive and need to be configured with an IP address via a software utility. If you get an old one a 5500CN instead of a CN2 you may need an older version of the IP configuration software.

Remember, you can also get c-bus dimmers/relays with built in power supplies so don’t just think about a stand alone power supply for your setup. Such units provide 200mA to the network and have a clock and burden option.

Although probably not recommended, you may be able to make your own power supply (or if you already have a bench supply) to provide the correct voltage with a current supply that must be less than 2000mA. The official power supply provides 300mA. A power supply providing somewhere between 25-30 volts would be ideal. As mentioned above, the power supply doesn’t have any other config options in toolkit.

Not sure if I would have any more luck than you with the transformer. Maybe just use your unit you are trying to fix as your power supply with the RS transformer instead of an emergency spare and save the funds in purchasing a power supply. Then you only need an interface and you are off and running with a workbench setup.

Most CBus units only consume 18-36mA so you will have plenty to spare with the 200mA from the unit.

Cheers

Jason

 

Oops!.

Just looked at your post again on my PC (instead of the phone) and noticed that your unit DOESN'T include the power supply! Sorry! So yep, you will need to organise a power supply (5500PS) or a dimmer/relay unit with a 200mA power supply included to get you up and running. Ignore my last paragraph in the post above...

Cheers

Jason

 

Doomed to failure. The low output impedance of a regular power supply will kill any commands being transmitted on the bus.

 

Hi Jason

Great minds think alike. I was able to find a good deal on e-bay for an 8 channel dimmer with C-bus power included so no additional 5500PS will be required. The photos look good and the seller has a 100% positive rating so I am holding thumbs the unit arrives in good working order. Now I just need a PC interface. If I can't find one for a good price I can temporarily remove and use the USB one on site seeing as it is only used when C-Bus toolkit modifications are made to the system and won't be missed.

Must say the price these and similar units are retailing for new nowadays is truly frightening. Exchange rate movements obviously played a major role but can't account for the full jump in prices from when I purchased dimmers and relays in 2017. When converting to ZAR the recommended retail on Clipsal's website is 2.5 times what I paid for the same unit in 2017, tax included both sides. That's a 150% increase.

The AUD vs ZAR shows the ZAR weakened (worst case scenario) around 33% during the same period from 8.93 (if you take the best ZAR strength in 2018 which is better than 2017) to 11.87. Does inflation really account for the balance after exchange rate movement? At these prices maintaining the system has basically become unsustainable and I might have to be become a permanent e-bay shopper

Thanks again for all your inputs!

 

Thanks for that sage advice Ashley. I will scratch that idea as an option for a test setup ...

Cheers

Jason

 

You got me thinking now Ashleigh... Constant Current Power Supply (therefore high output impedance) of a couple of hundred mA for a test bench

Recom RACD20-700-LP , Constant Current LED Driver Module 22W 31V 700mA from RS Electronics...AU$26

https://au.rs-online.com/web/p/led-...Ljk1SKda5EPjzJrWReYaApscEALw_wcB&gclsrc=aw.ds

 

I noticed this in the 5500PS installation instructions:
"Why Use a C-Bus Power Supply?
The C-Bus Power Supply is designed to have a defined value DC output resistance, and at the same time present a high AC impedance at the C-Bus communication frequencies (500 to 5000 Hertz). For this reason, standard off the shelf power supplies are not suitable for use with a C-Bus network. "

I am by no means an expert in this field but something tells me it might be more tricky than simply having a high output impedance. It seems like the "reactance" part of the output impedance, capacitive and/or inductive (which is frequency dependent), plays an important role and is tuned for specific frequencies? Also, do they specify 500 to 5kHz to avoid divulging the exact communicationfrequency of operation or does it vary in this range?

 

I agree 100% that a C-Bus power supply or dimmer/relay unit with a built in supply is definitely the way to go.

However, given that a $AU25 constant current supply with a low pass passive filter network tacked on the end may be a bit of fun to cobble together for a bench test unit...

Maybe it's my Medical Research background, but we just loved making equipment in our lab that did the same thing as the off the shelf stuff for a 1/10th of the price!

 

It would be pretty cool if you can get a DIY power supply with passive filter network to work Jason. Please post it here if you do.

As for my journey this side, thought I would give an update for whoever is interested.

So the Dimmer unit with inbuilt C-bus power supply which I ordered on eBay arrived and must say the shipment was extremely fast, I ordered Saturday night SA time and shipment tracking was already active Sunday morning. Received the unit on Tuesday. Price was less than a third of current Schneider RRP and it was advertised as brand new... you know what they say, "when it is too good to be true"... So obviously I had reservations and was eager to check it out. Started opening and everything looked good until I turned the unit on its side and noticed an odd defect. To be honest of all defects this is one I never would have guessed. The plastic housing is slightly warped on the one side as if from a factory fault when it was molded or whatever manufacturing method is used. Attached a photo. This obviously raised eyebrows so my first instinct was to "crack" open the unit and check the insides.

All the PCB's looked good except for the small one to the left where mains power comes in. On the underside it is pretty obvious some heavy manual soldering work was done. Notice the solder blobs on attached picture and discoloring in certain areas. It would be interesting to compare this to a new unadulterated PCB to see how much repair work was actually done and if it is still the original design.

Ok so the unit is obviously not brand new so let's close it up again carefully and see if it actually works. I didn't have much hope at this point... low and behold I power it up and everything works! A bit disappointed everything was not fully disclosed but considering the price and the fact that it works (hopefully not just for a while) I decided to let it slide. So I took the plastic housing from the old broken unit and dressed up the "new unit" with housing which looks respectable.

The next step was to turn my attention back to the old dead Dimmer unit and see if I can't get it working and dressed up in the warped plastic housing since I don't have another. Seeing as I still couldn't source a Thai Lin transformer I took your advice as per a previous post and attempted to drill and modify the PCB so that it can accommodate the RS Electronics transformer which was also delivered. I had to grind off some tracks, drill, and do some rerouting but it worked out nicely and this unit is also up and running! So now for a mini testing station I have two functional Dimmer units, one with C-bus power, a PC interface which I borrowed from site, and the semi-stable EDLT. The C-bus power from the "new" dimmer unit measures around 33Vdc so the EDLT is more stable and everything is working nicely. So happy I didn't throw this Dimmer unit away last year.

The only remaining concern is that capacitor just before the rectifier which I replaced with the first and best one I could find. The capacitance is obviously not the same as per design but I don't have any way of establishing correct capacitance. So if anyone at some point opens up an 8 Channel Dimmer without C-bus power supply and is able to check capacitance please let me know

 

That’s awesome news that drilling the PCB facilitated mounting the new transformer into your dimmer! Nice work!

Probably worth reporting the eBay user re: false advertising even if you don’t want to return the unit. Out of interest, was the warped plastic adjacent to where the internal soldering occurred and could it have been due to heating of the plastic from an electrical fault?

A great outcome all around. Maybe get a length of DIN rail and screw it up above the bench for mounting any units under test. You could also mount a mounting block/wall box to house the DLT.

I side screwed a mounting block to my equipment rack to hold a NIRT for IR broadcast in my house.

Just make it as safe as possible...

Cheers

Jason

 

Thanks Jason!

I did write a review and wasn't quite as generous with my rating as all the other buyers from the same seller but will leave it at that. The rapid speed at which it was shipped, the fact that it works and the price I got it for kind of makes up for the slight lack of transparency.

I wouldn't say the warped plastic is close to the soldered area. You'll note on the photo the plastic deformation is on the top near the face of the unit and the soldering occurred on the bottom side of the PCB in the bottom of the housing in this area. If I were to guess I'd say a unit was assembled with spares from different faulty units but who knows.

I like your idea regarding the DIN rail and wall box, definitely doing something like that! And yes safety first always!

Cheers
Tom

 

My bet would be a reject unit from the OEM that someone pulled from the skip.