MonsterBash
Well-known member
4900 Issue...best guess? ~Video added
I haven't capped it yet.. B+ was right at 130ish. I'm going through my caps tonight to make a 'kit'
Threw a known working Big Blue in...just cuz I had it
Any guesses as to what the problem is?
ETA video
ETA Progress update
So now I'm stumped...
Tried a know working monitor and works fine...thus the board and cabling is ok.
I pulled a bunch of transistors including 301..all were fine. I spent a good part of an hour with a magnifying glass looking for cold solder joints....didn't find any but touched up some questionable stuff.
As per the flow chart I change IC301..no change.
I found q302 bad..replaced it..no change
I couldn't get a reading out of the 85K Horz pot...changed that. Nothing.
Tried a know working chassis with the existing tube and yoke...worked fine
Did comparison readings on darn near every component to a working 4900
I also noticed that '30' looks like it might have had the wired jumper there at one time? I'm pretty sure I read that it's not necessary but I'm not 100% sure
I'm out of ideas...
I don't think it's a sync issue. Both the horizontal and vertical look solid...they are scrolling like i've seen with sync issue
I haven't capped it yet.. B+ was right at 130ish. I'm going through my caps tonight to make a 'kit'
Threw a known working Big Blue in...just cuz I had it
Any guesses as to what the problem is?
ETA video
ETA Progress update
So now I'm stumped...
Tried a know working monitor and works fine...thus the board and cabling is ok.
I pulled a bunch of transistors including 301..all were fine. I spent a good part of an hour with a magnifying glass looking for cold solder joints....didn't find any but touched up some questionable stuff.
As per the flow chart I change IC301..no change.
I found q302 bad..replaced it..no change
I couldn't get a reading out of the 85K Horz pot...changed that. Nothing.
Tried a know working chassis with the existing tube and yoke...worked fine
Did comparison readings on darn near every component to a working 4900
I also noticed that '30' looks like it might have had the wired jumper there at one time? I'm pretty sure I read that it's not necessary but I'm not 100% sure
I'm out of ideas...
I don't think it's a sync issue. Both the horizontal and vertical look solid...they are scrolling like i've seen with sync issue
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