Help with K7500

dbpbandit

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Hey guys, I've got a dead K7500 monitor that I'm trying to bring back to life. I've got power to the chassis but nothing past that, no neck glow, crackel, no nothing. Are there any common issues on these that I can look at first? Also, is a K7400 and a K7500 basically the same thing? I was checking out Bobs Monitor ID page and it only lists the K7400 but it looks (as far as I can tell) just like this one. Thanks.

Update:
I reflowed all of the connections at the chassis and on the neck board. Checked all connections and power but still nothing. I found a repair guid on line so I'll check the compomemts listed for possible failure according to the doc. Anyone know where I can download a schematic for this chassis? Thanks.
 
Last edited:
Recap it first, check the HOT and VR while you do so, and look along the back edge for cold solder along the big parts (and check that little transformer on the back edge for broken wires).

The K7500 is a little different than the 7400, but the concept of repair is about the same.

You should check the B+ at TP202 to see if it's high, low, perfect, missing, etc. That will tell you where to look next...
 
Recap it first, check the HOT and VR while you do so, and look along the back edge for cold solder along the big parts (and check that little transformer on the back edge for broken wires).

The K7500 is a little different than the 7400, but the concept of repair is about the same.

You should check the B+ at TP202 to see if it's high, low, perfect, missing, etc. That will tell you where to look next...

second all of this from my past K7400/7500 work. are you getting any ticking sounds at all?
 
No, no ticking or anything, it's lke it's not getting any power but I've allready checked that and power IS getting to the chassis. I'm still trying to find a schematic to download. Any one know where I can find one? Thanks.
 
UPDATE:
Did the cap kit, no change. I'll start troubleshooting the HOT and other components next.
 
Just a bit of my k7500 tips..

Replace the flyback of original.. Out of the dozen or so I've worked on, everyone of them had cracks or was blown up..

Check for a burnt resistor in the center of the chassis.. Also, go nuts with reflowing solder pads.. Pay attention to neck pcb, especially around the (3) trannies.. Replace the b+ cap on neck if you haven't already..

Good luck, these can be a pain.
 
Theres a small 8 pin IC in the power supply section that fires up the FET on the heat sink that runs the supply. If the IC is dead the monitor wont do a thing. Could also be a bad FET but they usually short.
 
Find out where your voltage does go to. Ive had so many cold solder problems with these chassis. The first thing i ever do when i start a chassis repair is just re-solder everything even if it looks OK. Check the 4 diodes in the power supply section. Check your low ohm resistors (Big white ones) (Some can be jumper-ed if there open temporarily) then keep at it. Don't give up you'll eventually fix it and feel proud of yourself. When i started repairing I worked on a chassis every other day for a year to get it working because I wasn't giving up. Lets just say i can now fix any chassis and I am brought all the ones that everyone says cannot be repaired. You will learn alot!
 
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