Viewsonic 17 power issue

Check for bent pins on the video connector. Check that the signal from your computer is not out of range for the monitor. The monitor should behave exactly like you described if it's not receiving a signal from the computer or is disconnected. Some may come on for a few seconds to show "NO signal" message then turn off. Aside from that, if you are hearing the degause coil fire up, chances are that you could have a problem in the flyback circuit or the high B+ on the power supply. Parts don't have to buldge, explode or smell to be bad.. You'll need a meter to check parts and voltages..... Shorted HOT, shorted diodes, bad caps... both in the main PS and flyback PS. And, maybe if you have a scope or Freq counter, you could check that the horizontal and vertical signals are making it to their respective circuits... just incase the video cable is bad. If this monitor is a monitor that is on a good amount of time, then I would pay attention to caps in the ps('s).

The schematic will be a general schematic for that series of chassis... not the monitor. So, there will be some items on it that's not included in your monitor that is a design for other chassis... however, the power indictor should definitely be shown... Follow the low B+... it should be there..... but, I don't think the power indicator will be the problem.

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Thanks SC - it is definitely internal to the monitor. I guess I'll have to start by trying to figure out how to disconnect loads. I was looking for the feed to the LED to see if I could eliminate some B+ lines. It is probably the 5V, but I thought finding it might give me a clue. I was thinking the 175V since the higher voltages are probably the last ones to come up. I don't know where else that goes but it does feed the degaussing crt. thru a couple of triacs. Strange implementation. It has to set a while, or if I read resistance on the power plug it may discharge something, so that the next time I power on the LED comes on for a sec. Otherwise it does not come on everytime I power on.

I guess the first thing to pull is the HOT.

thanks again

Bill,

Something to consider - unsupported refresh rates or resolutions can result in the symptom described. Whenever changing out different spec monitors, change the display to the most basic, VGA 640x480, before disconnecting the old monitor.

FWIW, my old Viewsonic 17 failed on a number of different resolutions, starting with the high refresh rates, over the course of two years, before finally failing completely on any setting.

Scott in Dunedin, FL

OK, I pulled the HOT heat sink with devices.

A 2SC4288A, I assume is the HOT, is shorted all the way around.

An IRFPF40, which may not be a transistor, is short on what would normally be base to collector. Open emitter to base. It is an International Rectifier device (hence IR...).

I know there are components like caps that can blow these out - anybody have a familiarity with this one?

The unit was working at home with the computer at the resolution that I have run forever. So it isn't an incompatible issue. The monitor will also take just ablut anything the adapter can give it.

The spec sheet for the IRFPF40 does not indicate the pinout. It is a "1000V Single N-Channel HEXFET Power MOSFET in a TO-247AC package"

Is it left to right, 1-2-3 = S-D-G or G-D-S?? the ohms 2-3 is - to + = 100 and + to - = 1k

thx

Hi!

That is exactly where I'd start. Get those caps out of there and test them, or just replace them and the bad parts. Then bring the power up carefully, and I'll bet you're back in business again.

If the monitor had a good picture, it should be worth repairing.

William