FSP035-1PI01 (Viewsonic VX910) inverter transformers?

[roothorick]

I've had a ViewSonic VX910 sitting in my livingroom for the longest time, and I just today took a serious crack at it. Symptom: Power light blinks green. Nothing appears on screen. Determined this to be the fault of the power board.

After some playing around and testing components, I noticed burn marks around the solder points for the primary winding of T1. So I just desoldered that whole half of the transformer and pulled it out of the circuit. The unit now powers up! Unfortunately, the backlight dies a second in, but I can still see picture if I blast it with a flashlight, so logic is running. Okay, I need a new T1.

Here's the question though -- can I actually buy these transformers anywhere, or will I have to buy a whole new board? I'd rather not troubleshoot a board I can't fix.

[PlainBill]

Re: FSP035-1PI01 (Viewsonic VX910) inverter transformers?

I've had a ViewSonic VX910 sitting in my livingroom for the longest time, and I just today took a serious crack at it. Symptom: Power light blinks green. Nothing appears on screen. Determined this to be the fault of the power board.

After some playing around and testing components, I noticed burn marks around the solder points for the primary winding of T1. So I just desoldered that whole half of the transformer and pulled it out of the circuit. The unit now powers up! Unfortunately, the backlight dies a second in, but I can still see picture if I blast it with a flashlight, so logic is running. Okay, I need a new T1.

Here's the question though -- can I actually buy these transformers anywhere, or will I have to buy a whole new board? I'd rather not troubleshoot a board I can't fix.

I did a quick search for FSP035-1PI01. Guess what - I found them for sale - as a matter of fact, I found two different versions for sale. One of them uses our old friend, the Royer oscillator. On that one the driver transistors fail and cause the problem you describe. I have no idea what the other version uses, but both are most likely repairable.

So if you want some help, take a couple of pictures of your power supply / inverter board and attach them to your next post. Use 'Manage attachments' (below the text entry area). I will want one of the top side of the board, one of the bottom side. And it really helps if they are sharp and will lit. Something over 1000 x 1000 pixels is good.

PlainBill

[roothorick]

Re: FSP035-1PI01 (Viewsonic VX910) inverter transformers?

I did a quick search for FSP035-1PI01. Guess what - I found them for sale - as a matter of fact, I found two different versions for sale. One of them uses our old friend, the Royer oscillator. On that one the driver transistors fail and cause the problem you describe. I have no idea what the other version uses, but both are most likely repairable.

So... you think the transformer is good? Since it powers up without T1 in circuit I assumed there was a shorted winding in T1, though I could see how a shorted Q6 and/or Q7 could cause the same issue, and I now see that removing T1 effectively took them out of the circuit too. The other backlight is most likely blown Q8 or Q9, but again, I don't want to further troubleshoot a unit I can't get needed parts for. I suppose the thing to do is lift T2 and swap it into T1's location, I'm pretty sure they're the same unit. Alternately, I could lift Q8/Q9 and move them to Q6/Q7. If it actually stays on but I still have backlight issues, the transformer is okay. If the switcher cuts, the transformer IS shot, and I'm back to square one...

It's the same board as here. (But with a different, white glue! heh)

[PlainBill]

Re: FSP035-1PI01 (Viewsonic VX910) inverter transformers?

Have you ever read Dante's 'Inferno', either in the original Italian, or an English translation? Actually, 'Inferno' by Niven and Pournelle would be more appropriate.

The cap sets the speed of the oscillator. The cap fails, the oscillator runs wild, and the transistors short. There is a zener diode in the circuit - make sure it is not shorted. The solution is simple - replace the transistors, the cap, and the diode if necessary.

Yes, I am sure that will fix the problem. As for the parts - the Belinea 101910 monitor uses the same power supply. The schematic and parts list are in the service manual.

PlainBill

[roothorick]

Re: FSP035-1PI01 (Viewsonic VX910) inverter transformers?

The cap sets the speed of the oscillator. The cap fails, the oscillator runs wild, and the transistors short. There is a zener diode in the circuit - make sure it is not shorted. The solution is simple - replace the transistors, the cap, and the diode if necessary.

You're talking about the three-legged diode that looks like a transistor, right? It's good. I actually messed up the screw that holds it down so I need to find a new screw :/ this is turning into a "fun" project.

So I have a failed cap? Which one? I don't have an ESR meter... or should I just recap the whole thing?

Yes, I am sure that will fix the problem. As for the parts - the Belinea 101910 monitor uses the same power supply. The schematic and parts list are in the service manual.

PlainBill

I'll see if I can find that service manual.

[alexanna]

Re: FSP035-1PI01 (Viewsonic VX910) inverter transformers?

You're talking about the three-legged diode that looks like a transistor, right? It's good. I actually messed up the screw that holds it down so I need to find a new screw :/ this is turning into a "fun" project.




I'll see if I can find that service manual.

Q 6 through 9 are available. When these fail they usually fail shorted. The tab and the center pin are connected internally.
These are the sot 23 small transistors on the back of the power supply, they are marked “DK”
Pictures?

[PlainBill]

Re: FSP035-1PI01 (Viewsonic VX910) inverter transformers?

No, the three legged diodes are rectifier diodes. The zener diodes are in the inverter circuit. They probably have identifiers that start with ZD.

PlainBill