Last time I powered it, my Iiyama HA202-DT made a cracking sound, similar to the sounds CRTs make when powered on, but longer, louder and ominous. The screen is completely black and, when fed a video signal, the monitor keeps "resetting" itself every few seconds (the same "click" it makes when changing video modes).
I suspect something in the high voltage circuit is blown but see no obvious sign of damage. Any ideas ?
Thanks in advance.
-- André Majorel It's a good life, bowing to a tyrant.
It sounds like the switching power supply is detecting an over-current situation and is shutting down, then trying to restart itself again. I would check the diodes in the secondary of the power supply and all large transistors and diodes in the horizontal/high-voltage section. John
Be sure to understand that Sam is talking about in-circuit ohmmeter testing. Out of circuit, B-E short is fatal.
I'm not an EE, but I had figured that much. :-) Thanks. If I can't get the schematics, I guess I'll have to desolder the transistor to make sure.
The 2SC5570 is spec'd for voltages in the kV range ; that makes it a good candidate for arcing. There were long "whiskers" of dust on the leads. Could an arc have developed that way ? Perhaps the replacement could use some heat shrink tubing on its leads...
-- André Majorel It's a good life, bowing to a tyrant.
"Charles Schuler" bravely wrote to "All" (13 Nov 05 16:56:59) --- on the heady topic of "Re: CRT computer monitor dies with loud crack"
CS> From: "Charles Schuler" CS> Xref: core-easynews sci.electronics.repair:348456
CS> Be sure to understand that Sam is talking about in-circuit ohmmeter CS> testing. Out of circuit, B-E short is fatal.
Most modern H-output transistors virtually have a near B-E short because of an internal damping resistor between 10 and 100 ohms. At least it will seem like a short on the 20K & 2K dmm range.
A*s*i*m*o*v
... You may be a tech if you're entertained by a 6-pack and sparking HV.
The DMM shows 1.1 ohm. Sounds high for a short, but it's the same figure if I put both probes on the same lead. :->
-- André Majorel It's a good life, bowing to a tyrant.
It's probably the secondary of the drive transformer causing that, remove the transistor and check it out of circuit.
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