Kortek KT-3301 [RESOLVED]

[Arm123]

Hey peeps.

I’m about to start replacing caps on this bad boy.

The brightness and contrast seem to be seriously low and dull.  The image is definitely there but is barely able to be seen.

Sometimes it comes in brighter for a second...  then goes back to dull.  Brightness and Contrast pots do nothing.

I just thought id post up to see if anyone has any schematics or quick fix suggestions ?

Here are a couple pics…   She has seen better days it seems.

Thanks,

















[edit]
Turns out that i tried to test the tube and the R, B guns were in the bad and the G gun was dead.  I tried to rejuvenate the guns and the R + B guns moved up a bit but the G moved a hair but was still close to dead.  So this tube is dead !

So sad.

[/edit]

[Arm123]

I have done some snooping around....   I removed the caps and most, if not all, of them seem to be reading with in spec. (capacitance test)

I started dicking around with those solder connections in the top right hand corner of my pic on the solder side of the board.  It appears as if they are there to fix board facture problem.  I re-soldered in a few places where i think it could be a 'flakey' connection and tested it out.

The picture is brighter...  but not all the way.  I have to crank up the voltage on the screen connection on the flyback and all the brightness / contrast controls.  This is an improvement, because i tried this before and still could not see the image.

Although the picture can be seen now, im still not happy with it.  I think i will go threw all the connections and redo / reinforce them.

I do have one small problem now.  The picture seems to be up side down / inverted..  what would cause this ?

Any thoughts / suggestions are appreciated.

Thanks.

[Ken Layton]

That's actually a Kortek monitor.

[Arm123]

That's actually a Kortek monitor.

Your a good man Ken...  Thank you

[Arm123]

Indeed you are correct Ken.  I found a pic..  looks exactly like my chassis.



I was just going by the label on the chassis. 

[Arm123]

Still no luck with restoring the brightness / contrast.  Ill post up a pic of the screen with everything cranked.

Anyone have any schematics or service manuals on this ?

[grantspain]

what have you replaced at the moment

[Arm123]

Hey there.

Feel free to tell me im not doing something correctly, cuz im relatively new at this.

I have gone threw all the electrolytic caps on the board and pulled them off to test them for capacitance.  All but 4 seem to be working within +/- 5% of rating.  I only replaced one of them cuz it was really bad and i had a spare on hand.  The four are:

C202 1000uf 16v  (reading in the low 900's)  Not replaced
C250 220uf 25v (reading in the low 200's)  Not replaced
C615 1000uf 35v (reading in the low 900's)  Not replaced
C702 10uf 50v (reading 5.0 - 6.1)  Replaced

Also, here are a couple pics i shot after cranking contrast / brightness / screen controls up.






I now notice that the 2 GREEN pots (green and green cut off) do nothing and green seems (to my knowledge) to be missing from these pics.   What do you think ?

Thanks.

[grantspain]

well it seems the green is certainly missing,this could be down to the input signal from the game board or the green drive transistor on the neck card or a faulty gun in the tube(maybe bent neck pin)
you can prove the game input by swapping the red and green wires on the signal input plug,if you then get the green you know its the game board output or wiring
your picture is upside down because you need to swap the yoke plug onto the other yoke connector

[Arm123]

Thanks for giving me somthing to go on mate.

Im willing to bet its the faulty transistor on the neckboard...   but we shal see.

Ill try all your suggestions and report back.

[Arm123]

Switched game boards, and the results are same, no green.

Switched v-red and v-green wires on the jamma, same result.

So i know it has to be something on the monitor.

I tested the three RGB drive transistors on the neck board...  tell me if im doing this right.  (BE) conducts one way, (BC) conducts one way, and (CE) doesn’t conduct ether way.  All three pass, so its not any of those transistors.

I also checked the pins on the neck board and see nothing bent.

I proceeded to check the other transistors on the chassis and I found that Q701 (SEC 550 bdx53c) fails the (CE) test...  I get a positive reading.

In your opinion would this mean that its fried ?

[Arm123]

Hey guys...  please look over here and help me take some sort of action with this thing.

http://forum.arcadecontrols.com/index.php?topic=73234.0

[Domolover]

I Have the Same Chasis, does this need AC isolation transformer?

Hey peeps.

I’m about to start replacing caps on this bad boy.

The brightness and contrast seem to be seriously low and dull.  The image is definitely there but is barely able to be seen.

Sometimes it comes in brighter for a second...  then goes back to dull.  Brightness and Contrast pots do nothing.

I just thought id post up to see if anyone has any schematics or quick fix suggestions ?

Here are a couple pics…   She has seen better days it seems.

Thanks,

















[edit]
Turns out that i tried to test the tube and the R, B guns were in the bad and the G gun was dead.  I tried to rejuvenate the guns and the R + B guns moved up a bit but the G moved a hair but was still close to dead.  So this tube is dead !

So sad.

[/edit]