Wg4961 power

Johndarlo

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Issue: chassis acts as if it's in HV shutdown. However it reads 140dc on the B+ rail. 160 and 139 across IC 501. IC301 has within range readings except for pin 11 which floats upwards in the MV range. There is no power to the neck and no neckglow. I saw one member who had a similar issue which turned out to be a faulty flyback. Just wants to run it by everyone for their thoughts before I drop $30 on a new flyback I may not need.
I have checked all the jumpers-good
B+ at 140
Power regulator and hot checked-good
Cap kit done
Replaced transistors that tested bad
Re flowed most of board
Any constructive thoughts on the problem?
 
your B+ is high and should be 130vdc so you have an issue with the regulator or the IC501 but 140 shouldn't be high enough to put it into HV shutdown.
 
Just so you don't get confused the only K4900 series chassis that has HV shutdown is the K4915. It is a medium resolution chassis and is identified by the small board that is mounted to metal heat sink of the chassis close to the STR351 (VR).

Did you check Q351?

If you replace IC301 install a socket for the new IC.

Double check the jumpers and make sure they are soldered good.

Don't know if you have a copy of the K4900 flowchart. If not here is the link http://antelopearcade.com/files/Monitor Manuals/FLOWCHART_-_WELLS_GARDNER_K4900_(U).pdf.

If you get stuck, hit me up and I can help you over the phone if needed.

Ed
 
Ed, thanks for the help. Still working on it. I used the flow chart and replaced ic301. I got high voltage to the crt for a few seconds and then nothing. Checked the voltages on the new ic301 and they were good for a minute or two and then went to crap. I'll keep plugging away. Sorry for the late reply.
 
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