I've had an issue with my 4900 for a while now where the screen will dim and I get some color bleeding. A quick smack of the cab would fix her for a while. Today I decided to take the time and find out what the issue was.
Found it pretty quickly, I had a bad pot on the neckboard. When I touched it, it would fix it. When I unsoldered it, it basically fell apart in my hand.
SO.....I have another 4900 neckboard and I examined the numbers on the back of the neckboard pots and "502" is what I saw on a few of the pots so I soldered a new pot on.
Turned it on and nothing. Dead. Pulled the neckboard and looked again. Oh shit!!
The pot I replaced said 501 not 502. After checking a schematic 501 is 500ohms. I f-ed up and put a 5kohm pot on there.
Found a 501 pot and slapped her in. Again, nothing dead. Fuse is good. I have no HV no nothing.
Before I pull the chassis and start shot-gunning this thing....Where should I start?
Found it pretty quickly, I had a bad pot on the neckboard. When I touched it, it would fix it. When I unsoldered it, it basically fell apart in my hand.
SO.....I have another 4900 neckboard and I examined the numbers on the back of the neckboard pots and "502" is what I saw on a few of the pots so I soldered a new pot on.
Turned it on and nothing. Dead. Pulled the neckboard and looked again. Oh shit!!
The pot I replaced said 501 not 502. After checking a schematic 501 is 500ohms. I f-ed up and put a 5kohm pot on there.
Found a 501 pot and slapped her in. Again, nothing dead. Fuse is good. I have no HV no nothing.
Before I pull the chassis and start shot-gunning this thing....Where should I start?


