No Red - Bad Pot?

daxwell

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I'm a newbie, so bear with my question if it seems simple. have a WG k4900 that has no red in the monitor. I've done some searching and and think I reached the problem. I'm pretty sure that the Pot on the Red Drive is bad. When I use my DMM and check the continuity on the Reg & Green Pots on the neckboard. here are the readings:

Test Leads / Green Drive / Red Drive
Pos Lead / Neg Lead
Left / Center - .7 / .7
Right / Left - 73.2 / .205
Right / Center - 73.0 / .204
Left / Right - 73.0 / .204

I'm assuming that the red drice pot is bad. Does Radio Shack usually carr pots that can be used as a replacement? I have a couple of extra pots from an EZ20 invereter board, Can I use one, I know the orientation of the adjustment knob will not be correct?

Is there something else I should check, or is this the most likely cause?

Thanks
 
logical approach is to swap pots.

when you're missing colors, you swap drive transistors, if no go, then swap pots, if no go, then resistors (the big ones that match with the drive transistors), if no go, then you're probably looking at a tube issue or something else.

by something else, it could be the actual video signal header at fault. you can skip the part swaps by reflowing the solder joints on EVERYTHING I just mentioned, sometimes you might get lucky and it's a cold solder issue.

also, does tapping on the side of the cabinet result in any flickering on the monitor? if so, that's a guaranteed cold solder issue. particularly if your missing red flashes. :)
 
good luck with this and keep me informed. I have the same issue with my k7000 and its not the pot, transistor, or resistor of the neckboard. I also checked the tube and its not that either. The problem is somewhere on the chassis, but now it has vertical collapse as well.
 
If I go to Radio Shack, what Pot do I buy - 1K, or 10K Ohm, and can someone tell me what type of transistors so I can check to see if Radio Shack sells these also.
 
skip Radio Shack. they may have the pot you seek, but the transistor, forget it.

read the numbers off the parts. the pot will say what its resistance is. the transistor you will need to read the numbers off it, then do a cross reference search here: http://nte01.nteinc.com/nte/NTExRefSemiProd.nsf/$$Search?OpenForm

once you have the NTE number, then head over to www.Mouser.com and search for that NTE replacement part.
 
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