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Main => Monitor/Video Forum => Topic started by: ToplessZ on April 02, 2008, 10:10:14 pm

Title: K7000 Shuts down when I try to measure voltages
Post by: ToplessZ on April 02, 2008, 10:10:14 pm

I bought a K7000 chassis on ebay, when I first tried to turn it on nothing happened. So I checked the board and found a missing cap c50.  I replaced it and also noticed that a large resistor next to it was loose so I fixed it.  Then I hooked it back up and it fired right up.  I noticed that there seemed to be smoke coming from it and the neck was glowing a little brighter than it did with the normal chassis I had on there.  The picture was all crazy as well,,So I did a cap kit.  Turned it back on(I didnt hook up the video cable though) and still the same glow and smoke(I kinda thought since it was an old chassis that maybe something was just warming up but I then decided to check the b+ voltage, as soon as I touched the frame with the negative end of my mulitmeter the monitor turned off and fried my fuse on my ISO setup.   What the hell happened?? 
This is the 25" P538 chassis..

Title: Re: K7000 Shuts down when I try to measure voltages
Post by: qrz on April 02, 2008, 11:04:34 pm

one has to be careful purchasing anything online !

according to the print ( www.wellsgardner.com/pdf/Scematics/k7000_25_27_inch.pdf  )

c50 is part of the vert yoke return . so, the vert output ic may be toast.  amongst other things,  as
this is a "HOT" chassis , and MUST be isolated from AC mains.

check the regulator circuitry and horiz out xistor (for possible shorts ) before reapplying  ISOLATED AC power.

qrz

Title: Re: K7000 Shuts down when I try to measure voltages
Post by: SavannahLion on April 03, 2008, 03:58:15 am

Quote from: qrz on April 02, 2008, 11:04:34 pm

according to the print ( www.wellsgardner.com/pdf/Scematics/k7000_25_27_inch.pdf  )

It appears that that link is dead?

Quote

as this is a "HOT" chassis , and MUST be isolated from AC mains.

Can you clarify this point? I've haven't really grasped the purpose behind the isolation transformer. Is it for safety reasons?

Title: Re: K7000 Shuts down when I try to measure voltages
Post by: Lutus on April 03, 2008, 08:29:24 am

The K7000 WG should have a shutdown circuit that will not send power to the anode if the input voltage rises above a certain amount.

Make sure the diode for this shutdown circuit is good and soldered in correctly.

You can read some about my exploits with similar issues here...

http://forum.arcadecontrols.com/index.php?topic=76968.0 (http://forum.arcadecontrols.com/index.php?topic=76968.0)

Title: Re: K7000 Shuts down when I try to measure voltages
Post by: qrz on April 03, 2008, 04:00:25 pm

i should know better than attempt to type addy's when tired -sry !

try agn     www.wellsgardner.com/pdf/Schematics/K7000_25_27_inch.pdf 

yes, it is a safety issue:
a hot chassis will be approx 70v above ground .  a properly functioning isolation xformer removes the damage risk to the monitor, connected periphial circuitry and/or any line connected test equipment...
there is NO physical connection from primary /secondary sides of transformer . the coupling is due to mutual inductance in the presence of a electro-magnetic field.


qrz