need capacitor wisdom

[gatesofmemphis]

I have a Viewsonic monitor VA1703 that just started going blank, connected or unconnected to the computer, less than 5 seconds after powering on.  Everything I've read about this problem points to (a) bad capacitor(s).  I was able to take the monitor apart fairly easily but when I looked at the capacitors, none had the obvious doming that I read was the real sign of a bad capacitor.  Attached are some photos as close as I could get them:

Does anyone see anything in the pics of bad capacitors? (The empty slot is a capacitor that _seemed_ to dome slightly).  Replacing it didn't fix the problem)

I thought about testing them with my DMM (a Centech P37772) but for the life of me can't figure out how to test capacitance, even after reading the 3 steps in the manual.  It has an adapter for capacitors with short leads but the adapter has only a single lead coming off of it (pictured).  Also when I put a new capacitor with long leads in the capacitance slots, I get no reading except 1.  

Does anybody have any experience with this Harbor Freight gadget measuring capacitance?  If so can you explain how I use the adapter and how I measure a capacitor in the Cx sockets?

Of course the problem with the monitor may not be at all capacitance related, but the symptoms point to it -- lowering the brightness extends the time the monitor stays on before going to black.

Thanks in advance.

Roy

[Ben Eishen]

Your "F" scale is used to measure capacitance on your dmm. To test the capacitance one side of the capacitor must be UN soldered or it will give a false reading. But sometimes a capacitor might read the right capacitance but be bad. This is due to the "ESR" of the capacitor.

Two easier ways to tackle this.

A) just replace all the caps with new ones. Usually you can "recap" a monitor less than 20 dollars.

B) pick up an esr meter and test all the caps. Then just replace the bad ones. You can use an esr in circuit since the voltage is low enough it will not turn on any semiconductor devices.

[Ed Stafford]

Most of the bad electrolytic caps I've seen are obvious.. usually either leaking their contents onto the board or blowing out the top.  I would be interested in 'IC904, which I'm guessing is an SCR.  It appears to have discoloration on the back.

Diagnosing a TV/Monitor is not a trivial task.  The best thing to do, imho, is start at the power supply and move forward.  What you are describing could be a couple of dozen things including a faulty thermistor, a short in the high-voltage circuit, a bad on-board circuit breaker, a bad voltage regulator..  Normally I start by grabbing a magnifying glass and inspecting every component for burn/scorch marks, then breaking out the DMM, taping the probes so you don't accidentally short something out, turn on the power (VERY dangerous.. be careful!!) and start checking voltages to see where I lose it.  If there are multiple boards, it helps to remove them to perform circuit isolation, which can help considerably.

--
Ed Stafford

[Cliff Gurlen]

C920 looks a bit swollen, but I'm with Ben on this one - "just re-cap it."

cliff

[gatesofmemphis]

Thanks everyone. I believe I will recap it.