Technosat 9800 digital satellite receiver -- no power

[elmousa68]

I have a Technosat 9800 digital satellite receiver which when it is plugged in and switched on remains dead. Nothing appears on its front panel. The unit was in perfect working order and this happened suddenly (I am guessing maybe it was on for a long time and over heated if that is possible).I am a novice in electronics troubleshooting so if anyone has a schematic for this device or can share a few ideas on how to go about fixing it, it will be greatly appreciated.

 

[Resqueline]

There could be a dried-out capacitor or a broken resistor in the power supply. Open it and post a picture of the PSU and maybe we can point to the potential culprit.

 

[elmousa68]

Technosat 9800 board

OK, I got an image of the board. I got the section that (I think) represents the power supply in the board. The IC pointed to by 1 in the image is an "Off-line Switching Mode Power Supply Current Mode Controller". So is no. 3 but they have different numbers. No. 2 is a single phase bridge rectifier. What next? Could it be a capacitor problem or an IC problem (or a resistor problem, although I doubt that since the board is in very good condition and I presume resistors rarely blow).

 

[Resqueline]

It was a very small picture but I can tell you the PSU is not in as good a condition as you might think. The cap in the upper right hand corner of the picture is blown.
There are also no less than 6 small electrolytic cap's in the central part. Those are prone to drying out, and if they are - the PSU won't be able to start.
I was surprised myself the first time I learned that the 1W 100k startup resistors sometimes fail, after not so many years, with no physical signs.
The blown cap might have resulted in damage to other circuits, let's just hope not.

 

[elmousa68]

Cap OK

Thank you for your input.

Eventhough the capacitor in question has signs indicating that it is blown, upon testing it displayed normal behavior. Just to be sure, I went ahead and replaced it. That did not fix the problem.

Any ideas?

 

[davenn]

1) check all resistors with a multimeter
2) I presume you have checked the fuse with a meter ?
3) check for any of the DC voltage rails, make a note of what they are
4) if you are electronics competent, look at the HV DC side of the PSU preferably across the pins of that large brown electrolytic in the lower centre, should be somewhere ~ 300V + - ~ 20V
5) Personally, a Res hinted at, I would be replacing all the electrolytic caps on the board they ARE the most unreliable electronic component in existance.

Dave