RVR PTRL-LCD transmitter PS

Gotta watch those Fresnel zones!
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Joe Friday
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Joined: Tue Dec 16, 2014 3:47 am

RVR PTRL-LCD transmitter PS

Post by Joe Friday » Wed Oct 03, 2018 3:22 am

I have a RVR STL transmitter with a defective power supply. The RVR P/N is FLY100SMD/5. I have not had much luck repairing switching power supplies, but would like to give this one a shot. RVR wants $375 for a replacement. Does anyone happen to have a diagram for this supply? Any experience with repairing one?

This was an ebay purchase, and they listed it as not always powering on, and the listing shows the unit working. Of course when it arrived the PS is completely dead. I know this is not unusual for a dyeing switcher.

Thanks!

Kevin

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davek
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Location: Sydney, Australia

Re: RVR PTRL-LCD transmitter PS

Post by davek » Wed Oct 03, 2018 4:56 am

I've seen photos of this power supply and it doesn't look to be overly complicated.
In the absence of a schematic I'd suggest a couple of things to try:

1. Check for any obvious problems on the primary side - open main fuse, shorted/open main rectifier, etc.. Also check the main switching FET, it should read high resistance ( >10k) between all terminals.

2. Check and replace any suspect electrolytic caps, especially small value ones on the primary side.

3. Identify the main PWM controller IC (which is usually on the primary side) and find the data sheet for it. Usually there is an example circuit in the data sheet, and it would give you a good starting point for checking things - is there supply voltage on the Vcc pin, or is there a FET drive signal coming out of the IC? Operation of the PWM IC could be checked by powering it with a bench supply and looking for output waveform..

TPT
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Re: RVR PTRL-LCD transmitter PS

Post by TPT » Wed Oct 03, 2018 6:11 am

On one of the models of this STL (sold by Armstrong, but essentially an RVR) I discovered that if the fan quits, the power supply is powered off (probably current sensing--no current draw by fan--supply shut down to prevent over-heating).

So...replace the fan. On the unit I had even a small CPU fan was enough to get the supply back on.

DaveSt
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Re: RVR PTRL-LCD transmitter PS

Post by DaveSt » Fri Oct 05, 2018 12:22 am

The circuit diagrams for the supply are not in the manual. There is a good chance that RVR will not even have them. In additions to the checks mentioned earlier, look for a high value resistor on the primary side of the supply. It will be connected to the unregulated DC supply capacitor and provides the DC supply for the SMPS IC. It could be in the hundreds of kOhm range. Just be careful as when these resistors go open circuit on a SMPS, the unregulated DC voltage can remain on the capacitor for a few days.

Joe Friday
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Re: RVR PTRL-LCD transmitter PS

Post by Joe Friday » Sat Oct 06, 2018 5:39 am

Thanks to all that replied...the tip about the fan is great. I have another fan that I will substitute and see if that is the problem. The suggestions on how to proceed with troubleshooting are most welcome. I have repaired numerous linear power supplies, but have almost no experience with switchers. I was hoping that RVR had used a "generic" power supply, but it looks like this is a custom unit purpose built.

Thanks again!

Kevin

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davek
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Location: Sydney, Australia

Re: RVR PTRL-LCD transmitter PS

Post by davek » Sat Oct 06, 2018 8:47 am

It might be custom built, but most certainly based on a fairly standard design. Good luck with it :)

DaveSt
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Re: RVR PTRL-LCD transmitter PS

Post by DaveSt » Sat Oct 06, 2018 9:44 am

An old saying: Google is your friend, or in this case Bing. A search for the power supply part number finds this manual:

http://3-mtr.info/manuals/RVR/TEX30LCD/ ... CD28NS.pdf

The TEX30 has the same PSU and has the circuit diagrams you need. For safety, check R4 first and make sure there is no voltage across it before you remove or start fault finding on the board.

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davek
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Location: Sydney, Australia

Re: RVR PTRL-LCD transmitter PS

Post by davek » Sat Oct 06, 2018 6:29 pm

Nice find Dave!

R4 on the main board is the start up supply resistor, so probably not ideal for measuring residual voltage stored in the main filter caps. In the past when I've worked on power supplies with no bleeder resistor across the main caps, I'll temporarily connect a 100W globe in parallel with the main filter caps via a switch. When I want to discharge the caps I flip the switch..

Question: what does the power supply do when you try to power it up - does it emit a tick-tick-ticking sound, or is it dead silent?

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