High B+ K7201

Dtrini

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Hi everyone,

Just joined the forum this afternoon and I am having problem troubleshooting a high B+ Voltage on the following Wells Gardner monitor
Sticker on the Horz. Transistor: WGM-1972-U2BS05G
054A7200-001
Google 054A7200-001 and got a schematic 19K7201 that is identical.
Primary side of T3 – 164V
Secondary side of T3 – across C101 187V and drops to around 167V (schematic shows 126V)
C57 – 100uF / 160V reading 0Uf was replaced.
I can see a glow at the corners of the monitor and hear the HV when it is powered up but there is no filament light or raster.

Any assistance will be greatly appreciated.
Thank you
 
replace the regulator. Also check the hot and rectifying diodes etc. B+ usually wont be high unless something krapped and took out the regulator.

Im afraid the 7200 might be the newer "evil" k7000 and if thats the case forget what i said. I havent been able to mess with those yet.
 
Last edited:
Cadillac

I replaced the regulator ic KA3842B, problem still exist.
Did a voltage check on the pins of IC001 and Q001 and the readings are way above the manufacture's recommended values also checked the HOT.

Thanks
 
Modessitt,

Excellent! Pulled D10 raster is coming up does this mean that a component shorting.
My first post was in technical-videogames-general repair and help, realizing I made a mistake another post was made in this forum. Apparently someone transferred my first post. Can I delete it?
Haven't read the FAQ fully, will try that during the course of the day. Do humbly apologize.


Blitz 8255
voltage at pin 1 of IC1? the LM1203 - 0.307V
 
Problem solved: Changing CO15/C011 brought up the raster.

Sent an email to the technical department at WELLS Gardner and was advised to replace these four capacitors C20/C21/CO15/C011. Three days ago I checked these capacitors on an ECG CX-920 capacitance meter and all checked good but decided to replace them as the company asked just in case they were breaking down under load.

CO15: 100uF/35V – meter reading 107.8uF
C011: 22uF/25v – meter reading 22.4Uf

Now have another problem a blue raster, if I scope the signals to the red and green drive circuit I should be able to see where they are dropping off. Correct me if I am wrong.

Thanks
 
Well, assuming your blue isn't cranked all the way up...

The first thing to do is pull the blue drive transistor to see if the blue goes away. If not, then you probably have an internal tube short that MAY be cleared out with a rejuvenator.

If the blue goes away, swap the blue transistor with the red transistor. If you still have all blue, then concentrate on the blue circuit from where it comes into the chassis (about 2vdc) into the color processing chip, then out (at about 6vdc) to the neckboard, and through the drive pots and drive transistor to the neck (along with some caps and resistors and such). If your picture changes to red, then replace that transistor...
 
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