19K7900 works great w/o IC4. What's up?

mrsodapop

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Hi All,
I got a 19K7900 in that worked fair with some minor issues. Decided it just needed a cap kit. While doing install, I noticed it was missing IC4 (Volt Reg.), so I installed a good used one, and put everything back together. Monitor would not fire up, and big white resistor on side got very hot. I than pulled chassis and removed IC4. put chassis back it and fired it up. Picture looks great. There is a very slight wave in picture, and my B+ is 109vdc. Supposedly this monitor has been in service for a while this way. Any Ideas why it works so well with out IC4, why does it not work WITH IC4 installed? How do I now get rid of the slight(hula) wave?
Thanks for any info
Aaron
 
Let's see a pic of this wonder chassis. It's possible it was hacked with a VR installed elsewhere, and your installing an IC4 gave it two...
 
Here are some
 

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And a few more. The last one is a screen shot( a little blurry from me shaking in cold garage)
 

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Let's see a pic of this wonder chassis. It's possible it was hacked with a VR installed elsewhere, and your installing an IC4 gave it two...

Or if its been hacked to work without a VR and is only getting 90-100VAC from the transformer you would end up with +10-20% more DC voltage which would be close to 109VDC. A better pic of the bottom of the board where the VR goes would help narrow it down.

FWIW I've never seen a K7000 without a VR. I've heard of people doing something similar with k6100's though.
 
Been really busy lately, so just getting back to catch up on some posts. The owner came and picked it up last Tues., but I did get a few pics. real quick be fore he took it.
The monitor came out of a Toobin game that I have not seen, I was testing it in a (stock) Gyruss cab., so I have no idea what kind of power transformer the Toobin is using. Here are some of the pics. I took of the IC4 section. Let me know if anybody has an idea how this was working so well w/o IC4.
Thanks
Aaron
 

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Been really busy lately, so just getting back to catch up on some posts. The owner came and picked it up last Tues., but I did get a few pics. real quick be fore he took it.
The monitor came out of a Toobin game that I have not seen, I was testing it in a (stock) Gyruss cab., so I have no idea what kind of power transformer the Toobin is using. Here are some of the pics. I took of the IC4 section. Let me know if anybody has an idea how this was working so well w/o IC4.
Thanks
Aaron

Hell, I want to know how a Toobin' monitor was working in a gyruss:)

Toobin' requires a medium resolution monitor....Gyruss is standard resolution.

Edward
 
Not that I have ever tried it....
But looking at the schematics, removing IC4 doesn't actually break the B+ circuit. So basically you have whatever the input voltage is going straight through R301 (the big white resistor) and carrying on from there.
IC4 may have been removed due to a problem in that circuit, hence it causing R301 to go nuts.

Your "hula" problem is most likely voltage regulation of sorts. (regulator or filter cap related)

Measure the DC voltage on both the red and blue side of that resistor.

I'm just speculating.
 
Kevin,
Thanks for your input, it seems the most logical. I did measure both sides of R301, one side was 109vdc (B+), but I forgot what the other side was, I believe it was a little higher. I had 122vac coming into the monitor from iso transformer on my Gyruss test rig. I was a little leary of giving it back to the owner and returning it back into the wild with such an unknown situation, but he really wanted to get his game back up and running. As far as I know it has been put back into service for almost a week and have not heard back from the owner, so I must believe all is well. Any ideas on long term usage this way?
As far as Elutz's question, I have not seen the game, nor have I seen/worked on a Toobin in a decade or two, so I can't offer a answer on that one either.
Thanks guys for your input
Aaron
 
I did measure both sides of R301, one side was 109vdc (B+), but I forgot what the other side was

I actually missed that in your original post....but yeah, that is too low for either side of that resistor. Probably why it had the hula thing going on.

Next time I have a K7000 out of any kind I'll have to play around with removing IC4 just for kicks.

Guess you'll just have to wait and see how it holds up.
 
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