P538 K7000 Chassis

boy141

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Hey Folks,

New guy here. Read almost everything that has K7000 and "white raster." So I have a Zenith monitor attached to a K7000/P538 chassis in a Simpsons arcade cabinet. When I first bought it and turned on the arcade, the flyback was arcing and zapping (I almost peed in my pants) but I had a white screen - no images, Just white.

So I bought and changed out the flyback and a cap kit with no filter (thanks ian). Then I read to change out the horizontal output transistor - 2N3904 (not a chinese clone). So after all this, I powered it back on - STILL WHITE. No image or anything. I adjusted the source POT, and I get white when I turn it all the way up and black in the opposite direction. Looks like I have raster (which is good, right?)

After getting fed up with no image, I just ordered the ceramic resistor 2R7ΩJ 7 watt (i think it's R104), the cap filter, and a IC4 - STR30130 VOLTAGE REGULATOR. So if this round doesn't work, WTF do I need to do?

Forgot to mention that I HAVE NECKGLOW, and the arcade is playing blind! I put coins in the machine and hear the 'add credits sound.' I measured the RGB input to the chassis board have some current.

TL:DR
Put in a new cap kit, flyback, and HOT.
I have neckglow and raster.
Will replace IC4, R104, and filter cap.
About to give up.
 

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why are you replacing the HOT when you have a picture? also it's a D1394, not sure where you arrived at your part number. if the HOT wasn't working you wouldn't have high voltage; it wouldn't be working at all.

why are you replacing the voltage regulator? it's obvious that your monitor is on and functioning. if it was in high voltage shutdown I would buy your theory on replacing this part.

why are you replacing R104? why are you replacing the filter cap?

this is a very intriguing repair strategy you have. first of all, the Screen adjustment on your flyback is too high. you see those diagonal retrace lines? you should never see those. turn that down.

next confirm that you actually have a signal plugged into it. if you don't have a plug with wires attached to the signal header on the right side of the chassis, you're not feeding it anything to display. if this is present I would suspect that your power supply is not working to power the game board; contrary to popular belief, said power supply has absolutely nothing to do with your monitor.

that K7000 sticky thread is the KLOV equivalent to WebMD. it's become a 25 page or whatever convoluted mess of a variety of people's opinions.
 
Hey!
why are you replacing the HOT when you have a picture?
Well the flyback was arcing like mad so I though the HOT was damaged.

Everything I have replaced or will replaced was from that 25 page mess. I wished they had locked that thread!

next confirm that you actually have a signal plugged into it. if you don't have a plug with wires attached to the signal header on the right side of the chassis, you're not feeding it anything to display. if this is present I would suspect that your power supply is not working to power the game board; contrary to popular belief, said power supply has absolutely nothing to do with your monitor.

I have the wires plugged in (RGB are closest to the door of the cab while two black wires are facing towards the coin mech). I'll post pics later.

But my question is, if the game is playing blind, doesn't it already have power (enough)? I've tested at the harness and I get 12v, 5v, -5v. I might crank up 5v to 5.2
 
Post a pic of how you have the RGB and two black wires hooked up. Unless someone modified the wiring harness, there shouldn't be two black wires running to that connetion. Without seeing it, sounds like you have two grounds possibly running to the video sync. Again, this is a theory, without seeing pics. Trace the two black wires back, where do they come from?
 
Leave everything that you have mentioned about replacing alone. Those parts are all working properly.

Your problem lies either some where in the video input part of the chassis or as mentioned earlier wired incorrectly. There should be a white wire in the group of wires going to the input header for the video. That wire should be on pin 10 (pin closest to the front of the cabinet).

As you can see on the schematic the sync input is to the base of Q7. I have seen a bad Q7 cause this same problem. If Q7 is defective your sync signal stops there. Just like not having a signal connected from the game board. Q7 (2N3904) can be gotten at Radio Shack. They are a dime a dozen. Not saying that is what is wrong. However it's worth a shot.

Always remember that pictures are worth a thousand words to us out here in helping you troubleshoot your problem.
 
And we're back. Here are some pics part 1.

The chassis and how it's connected in the cab:
UKcI3Wn.jpg


The RGB header cable
mvv82nH.jpg


The black wires are connected to a grey and black wire. the grey wire goes to sodder side 13 and black wire goes to component side 14:
1oZNbmS.jpg


The neckboard
Cb7zuhE.jpg

xEAoj0Y.jpg


Q7 area
mvv82nH.jpg

AgjaWvg.jpg
 
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Part 2

Top of the chassis board:
VWX2bMj.jpg

Vi4pEqK.jpg

jt9OqSd.jpg


Bottom of chassis board:
z0U00wY.jpg

qzawzJy.jpg

tGVzx8B.jpg


Old (left) HOT with the new HOT (right)
tO2UwaA.jpg


Will go to radioshack and replace 2N3904. I haven't replaced IC4, R103, and filter cap cause you guys told me not to.

If you need any closeups of anything, hit me up. Also, I can't find pin 10! I looked at the pictures from the K7000 pdf and seriously can't find it. Can someone post a pic of it and highlight Pin 10 ?

Thanks guys.
 
This is the Pin 10 ecwestjr was talking about, looks ok.

PIN_10.jpg


The soldering on C204 on the neckboard doesn't look too good. It's an important cap, part of the Video B+ Circuit.

C204.jpg


Also looks like the ground wire going to P202 on the neckboard has been snipped/broken

P202.jpg
 
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When I get off work tonight, I'll fixup C204. Can I ground P202 to the black wires located above the silk screen P448 ?
 
That wire is snipped because it's pointless as the trace is interrupted anyway (doesn't look accidental though, more like a factory thing). Grounding of the relevant parts is through a wire on the other header.

I would rather check voltage at the collectors of the video output transistors (Q201/202/203). You should have less than 130v but at least 110V or so. The collectors of said transistors are of course the same as the tabs and those are covered with tape and they shouldn't be. If you don't have voltage at the collectors check voltage on the area connected to the + side of C204. You should have 130V there when all is good.
 
...(Q201/202/203). You should have less than 130v but at least 110V or so. The collectors of said transistors are of course the same as the tabs and those are covered with tape and they shouldn't be.

Will look into this. When the flyback was arcing, one of those transistors was touching each other (Top metal part). i taped and spaced them out. Might replace those at this rate.
 
That would explain everything.

Replace things only after you find them faulty.
 
I removed Q201, Q202, Q203 and tested the resistance. None of them shorted.

Q201 has value of 795 and 789
Q202 has value of 700 and 766
Q203 has value of 663 and 739

i reflowed the sodder on the neckboard so we good on that one. So i'm guessing remove the crt and from the cab and test it on the bench? Any idea how to test IC1?
 
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so i tested the input signal from the back of the neckboard:
Q201 130/.2
Q202 .6/.7
Q203 0/.7

I tested IC1 pins:
inputs:
R:3.7
G:3.8
B:3.7

Outputs:
R:.83
G:10.6
B:5.6


pretty much guessing that Transistors C2068 is toasted?
 
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so i tested the input signal from the back of the neckboard:
Q201 130/.2
Q202 .6/.7
Q203 0/.7

Not sure what you did there. Let's try again: what voltages do you have on the points marked with the yellow, red, green and blue arrows?

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Morning!

So here's pictures of what i did

But the readings are
Red: 130
Green: 8.14
Blue: 5.674
 

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Looks like R208 and R209 are bad. Pull them out of circuit, test them (should be 6.8k) and if bad replace them.

While you're at it, check also R210, R211 and R212 (all 2.7k). No need to desolder them, just test them with neckboard unplugged from tube.

I can't see if you replaced C204. If not, do it.
 
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C204 has been replaced with a cap kit (thanks ian!). So there's 1/4, 1/2, 1w and 2w for the 2.7k resistor. Which one is applicable ?
 
Switched the multimeter to ohms and tested

R210 3.041 K ohms
R211 2.675 K ohms
R212 2.531 K ohms

just waiting on those transistors. it'll be monday.

sigh.
 
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