P538 K7000 Chassis

Are you getting replacements for R208 and 209 too? Those are the main culprit.
 
Well I'm back. I replaced the transistors tonight and waiting for the resistors to be shipped.


So when all the POTS are turned down, I get a green screen. When I adjust the POTS, I get a faint image. My red and blue are responding when I mess with the cutoff. Unfortunately, I don't think my green is doing anything.

And what sucks even more, my multimeter probe broke when the dumb thing fell from the cabinet (measured blue and fell). When I probe my red, I get 130 volts with the lightning bolt. The other two get like 8 or 13 volts with no lightning bolt.

Hopefully the pics make sense.
 

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try turning down the screen control on the flyback (the bottom knob) to get rid of the retrace lines. Bring it down far enough to where the blacks in the screen are black not grey. Then, on the remote board (the board with the 6 pots on it) adjust your contrast and blk level (might be contrast and brightness) to balance the picture out.
 
Well we got somewhere. The pictures are all bluey-white. Also, I turned my source close to black, but no picture when I adjust the contrast (all the up) and black (all the way down). The only way to see what's on the screen is to turn the source barely to white. This is the only way to test this. I changed out R207, R208, and R209 with the resistors you see in the picture. R210, R211 and R212 are a different size. What do I replace those with ?
 

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Why did you replace 6.8K resistors with 2.7K ones? The 2.7K are for R210/211/212. Look at the schematics!
 
turn the Screen pot down on the flyback.

if you have no brightness adjustment there then I would suspect cold solder at the G2 pin.

lol @ resistor replacements. you would've been better off sending this to Buffett.
 
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.



well crap. read this wrong. I'm pretty new to this, but getting the hang of it. Did i destroy anything else ? Ordered the resistors. try again later this week.
 
turn the Screen pot down on the flyback.

if you have no brightness adjustment there then I would suspect cold solder at the G2 pin.

lol @ resistor replacements. you would've been better off sending this to Buffett.

ikr? The brightness works. Just when I turn the source down to black, I get no picture. Turning it up just a tad works.
 
I don't mean to be a condescending prick about this, but seriously send it to Buffett or Arcadecup.

it's obvious there's much deeper issues than you can probably fix yourself. I think it's awesome you're trying your hand at it, but even Buffett will tell you that K7000s can be simple to fix and then there are others that are next to impossible to figure out.

I need to re-read the whole thread to see what you've changed so far.
 
I don't mean to be a condescending prick about this, but seriously send it to Buffett or Arcadecup.

it's obvious there's much deeper issues than you can probably fix yourself. I think it's awesome you're trying your hand at it, but even Buffett will tell you that K7000s can be simple to fix and then there are others that are next to impossible to figure out.

I need to re-read the whole thread to see what you've changed so far.

wish I could afford it. would rather learn it the hard way and pick it up. Learning a lot from you all though.
 
I don't mean to be a condescending prick about this, but seriously send it to Buffett or Arcadecup.

it's obvious there's much deeper issues than you can probably fix yourself. I think it's awesome you're trying your hand at it, but even Buffett will tell you that K7000s can be simple to fix and then there are others that are next to impossible to figure out.

I need to re-read the whole thread to see what you've changed so far.

I say let the guy learn. Good or bad, he's going to get an education.
 
then I will try my best to assist. I need to actually read the rest of the thread first. :)
 
then I will try my best to assist. I need to actually read the rest of the thread first. :)

I wish I had a resource like this when I started in Coin-Op in 1984. A lot more Tempests would have probably made it through the conversion years I'm sure.

:)
 
then I will try my best to assist. I need to actually read the rest of the thread first. :)

Thanks man! I just need guidance and support because I really enjoy this! Huge nerd here!
Things I've done:
1) Cap kit (no filter replacement)
2) Replaced Flyback
3) Replaced HOT
4) Replaced Transistors at Q201, Q202, Q203
5) Put in the wrong resistors at R207, R208, and R209.

Things to do:
Install the correct resistors for R207, R208, and R209
Install resistors to R210/211/212 .

now we wait for the postman.
 
If the two resistors don't get you going, There are a few voltages that create the image on the screen.

1. High Voltage, that's through the anode. since your Flyback is new, that voltage is probably correct.

2. Screen voltage, that's the one you adjust with the knob on the flyback, it's adjusting so it's probably working fine

3. Heater voltage. You can see neck glow, which is the heater voltage. Check the resistor on the Neckboard, R213. It should be 68 ohms or less. The tube itself could have a weak heater too, any of this will make your image dim like yours is. If you can easily see the neck glow, and by looking at your image, I don't think this is the problem.

4. Video voltage, since all three colors are weak it's not likely to be the resistors you're replacing or any of the three transistors, because all three would have to be bad at the same time. This is ran by the 12 volts, and the B+ voltage, you know the B+ is fine because the monitor is working, the 12 volts is probably fine as well because the sync uses it, and your monitor has sync.

So this leaves something in the brightness circuit, that affects all three colors. So you've got IC1, which rarely goes bad and is at least partially working.... and you've got Q8 which is a 2n3904, known for going bad from time to time... Also check C12 and make sure it's 1uf 50v, and C13 is 22uf 25v. Voltage can be higher but UF should be right. C10 should be 33uf 16v (or higher voltage)... check out Q4 too. C11 should be 22uf 25 v....
 
I had a fairly obscure issue on a monitor in an NBA Jam. the thing looked like a rat's nest was built in it, it was pretty gross. I wound up pulling the flyback and immediately taking it to the sink. the wires that run across the chassis were chewed up. even though there was probably nothing wrong with them I replaced them anyway.

I didn't know what to expect with it because when I started I found that there was no fuse on the chassis. that could mean 800 different things. but dropping a fuse in I was surprised it actually worked, but with one problem: it had this strange smearing of blue all over the screen. I wound up trading out parts between it and either red or green with no change.

finally I'm left with nothing else to try and just staring at it. it was then I noticed one of the little green poly caps had a leg broken off, in the blue circuit.

the moral of the story is sometimes you have to inspect the whole thing to make sure all its limbs are intact!

did you get the flyback from a reputable place? having no more Bob Roberts cures a lot of ills in that area now at least.
 

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maybe its the angle of the picture but this pot looks broken to me.
 

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and FWIW, those thin lines going left to right mean that you have the screen control on the flyback up too high. :)
 
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