KTMF Chassis monitor issue

Gonzo

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Sep 30, 2013
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Hey guys, I picked up a converted Cab with a 4-slot MVS that had been stored for a bit. The chassis says 25” RCA KTMF 2641M. When I plugged it in image was bad and would only read 1st slot and none of the other 3. Gave the carts a decent clean along with the MVS. Image look way better and able to choose all 4 slots. I still noticed colors aren’t perfect and certain scenes get a glitch on a game and sometimes it looks like the image gets smaller the bigger a bit but mostly depends on which carts is playing. Magical Drop 2 seems the worst at the white high score screen, glitches and screen gets bigger/smaller. This is my first CRT cab so this is unfamiliar territory. I was told to check B+ but not exactly sure where to do it at and what voltage it’s supposed to read? Am I correct thinking it’s the monitor part or would it have something to do with the 4-slot? Any help would be great.
 

Heinz

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You need to start at the cabinet's wiring and power supply first and make sure they are to spec / good working order.

Next you need a known working PCB to test and use that to adjust anything on the monitor that needs attention.

Pictures are a must if you want accurate guidance here.

Going straight to checking the monitors B+ voltage when you have no experience with CRT's is getting ahead of yourself. Start at the base, check the cabinet, the wiring, the pcb first.
 

Gonzo

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It’s been a while since I posted and forgot how to upload pics and videos, I did upload on Facebook but not sure if I can post a link here. Am trying to learn how to troubleshoot myself if possible but not sure what exactly to check or what numbers I should be getting. Am going off the number on the chassis but haven’t had much luck getting info.
 

Heinz

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The chassis PCB should have a row of adjustable pots for various things. Try those but please use a plastic tool.
 

Gonzo

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Definitely. Am go to look into buying some plastic TV tube tools. In the meantime am going to see if I can upload some pics that way I can get better help.
 

Gonzo

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Here’s a pic of the chassis.
 

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Gonzo

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Here’s where the screen starts shrinking and glitching then gets normal for a second or so and does it again. It does it multiple times till the scene changes.
 

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Last edited:

Gonzo

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Sep 30, 2013
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I was doing research and decided to check the 5V power at the PCB connector plug and was reading at 6.1X! I went ahead and started to adjust the power level and it immediately dropped to 0.62V. I didn’t hear no sound. Wasn’t sure what happened since I didn’t get to turn it and just gave it some pressure. I unplugged it and replugged and started back up. I tried adjusting again and this time turned a bit and started dropping then went down to under 1V once again. I repeated the process a few more time and the las one was about 5.30V and was able to turn without any issues till I got it to 5.12V and left it there. Is it possible to clean or repair the power supply or better off purchasing a new one? It’s a big brick looking one with a fan on top (don’t know exact name). Image looks a lot better along with colors but still get a slight glitch. At least seems am going in the right direction. Going to keep researching and reading.
 

Heinz

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Was it reading 6.1V at the jamma edge with the MVS plugged in!?
 

Gonzo

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Yes. On the back side of the plug connected to the PCB while turned ON. Top side number 3 and 4 spot.
 

Heinz

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You might've fried something running 6.1V into the 4 slot.
 

Gonzo

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Sep 30, 2013
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You might've fried something running 6.1V into the 4 slot.
I don’t think it’s the board, I tried my 2- slot on it and it did the same thing but when I install into my LCD converted Cab I have no issues.

wondering if am better off finding a good shop to have them check out the chassis board.
 
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