Main > Monitor/Video Forum
WG K7000 dead... flyback? (SOLVED)
Sarver Systems:
I already had one going, but I wasn't getting any replies. That's why I threadjacked this one.
http://forum.arcadecontrols.com/index.php/topic,135065.0.html is my original post.
menace:
This is out from left field but if you can get your hands on an infrared camera you can spot a hotspot very easily. I have revived many dead tv's, crock pots, monitors, power supplies by plugging it in, scanning for the hot spots and then starting there. Had a 32" tv that just needed a .25$ diode to bring it back to life.
I had a k7000 with a bad thermistor (upper right of the board if flyback is in the lower left). This caused it to power off intermittently...
qrz:
typical areas are
C57 47uF/160v
C56 22uF/160v
R101 cold solder BOTH ends
C20,21 10uF/25v x-ray shutdown
R89 cold solder
and cold solder on IHVT , driver xformers and driver/output xistors
i have seen D10 fail ( 10v zener ). but, is rare
voltage on pin 5 IC 2 should stay low ...
http://www.wellsgardner.com/pdf/Schematics/K7000_25_27_inch.pdf
buffett:
K7000's also suffer from ALLOT of cold solder joints and broken pads.
check it all over good for any thing that looks bad and re-flow it even if it does not look bad.
if you pull D10 and the chassis works then your VR is bad.
if you pull D10 and the monitor is still in shutdown then you have other problems.
a new flyback is needed before you can have any known good place to start.
if you are in the US and need parts i have them.
if you need it fixed i can do it for you.
email me threw my site the arcadebuffett.com
Peace
Buffett
MKFan4Life:
--- Quote from: buffett on January 14, 2014, 12:14:08 am ---K7000's also suffer from ALLOT of cold solder joints and broken pads.
check it all over good for any thing that looks bad and re-flow it even if it does not look bad.
if you pull D10 and the chassis works then your VR is bad.
if you pull D10 and the monitor is still in shutdown then you have other problems.
a new flyback is needed before you can have any known good place to start.
if you are in the US and need parts i have them.
if you need it fixed i can do it for you.
email me threw my site the arcadebuffett.com
Peace
Buffett
--- End quote ---
Sorry to bring this old thread back to life, but I am the original poster and life has generally delayed any work on this thing for 2 1/2 years or more. (Wife had medical problems and a couple of operations right after I started this thread.)
Anyway, I started working on this same chassis again and after pulling it out with intentions of pulling D10 to see if it fired up, I quickly found a large resister (R97 I think by D16 and D17) that was loose in it's holes. (Solder had completely cracked loose.)
I desoldered it and checked it to make sure it was still in spec and it was, so I reinstalled it with plenty of fresh solder. I then went ahead and installed a brand new flyback, and tested the HOT while it was handy to take it out of circuit (aiding a bit in the flyback removal since they are both attached to that heatsink), but didn't replace it as it tested good and although I had a new HOT, I had no new thermal paste.
Also tested the voltage regulator (in circuit though), and reflowed almost the entire solder side for good measure. Also tested all the diodes in the power supply section and compared readings to ones I found online to see if they were close (in circuit I admit). All seemed good.
Installed the chassis back into the frame and fired the game up. Seems to have gone into shutdown again. Checked B+ and it read 181VDC on one side and 182.5VDC on the other of the large resister on the left of the voltage regulator heatsink.
Next step tomorrow after work is to indeed remove D10 this time to see if it fires up, but until then, while I was at work I thought you guys might chime back in with ideas if the D10 removal turns out to be a dead end.
BTW, Buffett, thanks for the advice back in the past on buying the Pace MBT 250 (I'm TortureBot on YouTube). Messaged you recently about that connecting rod that broke in mine the first time I used it (darned Ebay, lol!). I bought a new part and fixed her right up, along with a new glass tube for the SX-70 solder extractor. (It was chipped badly upon inspection, too.) Works great at the moment. I used your methods for the voltage regulator testing in circuit, but not out of circuit. Looks like that's what I may be looking at replacing soon.
Any help is greatly appreciated guys!