K4600 vertical collapse after cap kit

sandmanx

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I picked up my first arcade game a couple of weeks ago, a Frogger cab with vertical drop on the monitor. I ordered and installed a cap kit from arcadeshop.com, and when installing everything back on, I reversed the blue and green wires on the yoke, which blew the fuse on the mainboard. After replacing the fuse and hooking everything back up again, I now have vertical collapse.

I reflowed all the connection pins on the daughtercards and mainboard, but I'm guessing the reversed wires may have blown something else, and I don't know where to start looking. Does anyone have any suggestions? The only test equipment I have is a multimeter.
 
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There are two vertical drive transistors on the X-Y board. TO-220 package, I cant recall the number. Check them, and replace if needed.. Dont ask me how I know...;-)

Andrew
 
Measure the ohm readings between the R and B tabs on the yoke, and between the G and Y tabs on the yoke. You need to check to make sure that you didn't blow the yoke...
 
The blue and red pair of yoke wires are the horizontal and the green and yellow pair are the vertical.

You have put horizontal voltages on the vertical output circuit and will very probably have blown (at least) the vertical output transistors as Andrew points out - also look for the fusable resistor that feeds these vertical transistors as it may be stuffed as well - cross your fingers there is no horizontal circuit damage.....good luck!
 
Thanks for the help guys. The yoke resistance readings are normal, and the vertical transistors are toasted. It looks like the resistor is ok. I'll see if I can find some replacement transistors tomorrow locally and hope that I didn't take out anything else...

Nothing like a self inflicted problem to welcome me to the world of crt repair! :eek:
 
I changed out vertical drive transistors just a bit ago and this is what it's doing now. The tear down the middle must be due to camera refresh refresh, but in any case it's no longer collapsed. What would cause this pattern?
 

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Well, that turned out to be the horizontal oscillator. I didn't have a plastic screwdriver to turn it so I pulled the x-y card out and gave it a half turn counter clockwise and happened to guess correctly.

Now the upper right corner is discolored and there is a slow sweeping bar from left to right across the screen. I'd guess the monitor needs degaussing for the discoloring, but I'm not sure on the sweeping, I'm going to try and find something non-conductive and see if the oscillator needs to be tweaked a bit more. I also checked the b+ and it was at 129.8V after about 15 minutes, which is fairly close to the 129V spec.
 
hi did you manage to fix this completely?

i just did exactly the same thing! :(

which transister did you replace?

is fact that you needed to adjust something and that still not 100% indicate some other component(s) on the xy board need replacing?
 
I'm having the very same problem. I successfully capped my 4600. But i ran into a similar issue when trying to fix the black level pot. I took all daughter cards out and sprayed the pots with electronics cleaner. I didn't over spray it, but i may not have given it enough time to dry. Anyways, when i plugged it all in i saw the vertical collapse and the monitor is now blank.

I was checking the ohm values and i have 150 for G/Y and 3 for R/B. I'm having trouble understanding what they should be from the schematic, but it doesn't look good. Did i blow my yoke?
 
I was checking the ohm values and i have 150 for G/Y and 3 for R/B. I'm having trouble understanding what they should be from the schematic, but it doesn't look good. Did i blow my yoke?

Are the batteries in your meter fresh? Weak batteries can cause incorrect readings. Naturally you measured the yoke with it unplugged from the chassis and power off?
 
Hmm. 150 for vertical is way high....

Did a retest. i have G/Y at 11 and R/B at 4.5. I had a light touch on the probe for the first reading. Still a novice when it comes to probing high voltage devices. It scary and feels like I'm trying to defuse a bomb.

thanks!
 
Are the batteries in your meter fresh? Weak batteries can cause incorrect readings. Naturally you measured the yoke with it unplugged from the chassis and power off?

Oh man.. No, it was all plugged in and running. Feelin' pretty dumb about that.. Powered off and disconnected from the chassis i get 0 for both.
 
Oh man.. No, it was all plugged in and running. Feelin' pretty dumb about that.. Powered off and disconnected from the chassis i get 0 for both.

Are you measuring the pins on the chassis or the connector from the yoke? You should be measuring the connector...
 
I was checking the pins on the yoke. Just tried it again after i removed the entire chassis.
The only thing i did different was measure with the neck board off. Now I'm getting a consistent 15 for G/Y and 10 for R/B. Is that okay?

thanks!
 
A little high on both. Check that battery.

Still, doesn't seem high enough for collapse. Did you reflow the solder to the daughtercard connectors?
 
A little high on both. Check that battery.

Still, doesn't seem high enough for collapse. Did you reflow the solder to the daughtercard connectors?

8 & 3.5 on a super fresh battery.

Yeah, i reflowed both daughter cards at the chassis and card connections. I just noticed a couple blown resistors on the card that connects the video. Well, they don't give any kind of ohm reading. So i assume they are blown.

I was attempting to replace the black level pot. My electronics store only had 2k pots so i put those instead of the 1.5k pots. It just so happens that one blown resistor is connected to that pot. Looks like that was a mistake. But the collapse happened before i did that.

Here is my order of events.
1. Successful cap kit repair.
2. Black was a little too high, not much play on the pot. Removed card and sprayed with electronics cleaner. Do not recall spraying the XY board because it didn't need any adjusting.
3. Plugged everything back in and powered up.
4. Watched the vertical collapse down just before the monitor went out.

Now there is no glow in the yoke and B+ was at 131V when i last checked.


thanks!
 
Okay, yokes seems good now. A 2K pot there shouldn't matter, as increased resistance means a darker picture.

What are the locations of those resistors? Check the manual to see what value they should be, then pull them and see if they are. if not, replace them. Also, check R422 on the neckboard. If it goes bad, it will cause the neck to not glow...
 
Those resistors actually tested good. But R422 gave me 3.8 when it should be one. Should i replace it?

thanks!
 
i have fixed my k4600 vertical collapse issue.

I tested the transistors on the XY board using multimeter in diode test mode and it confirmed that tr305 and tr306 were bad.

the schema indicated following codes for the transistors:

tr305 2SA490
tr306 2SC1625

I used a TIP31 instead of a 2SC1625 as i could not find supplier in UK.

Replacing the transisors resolved the problem :)
 
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