K7300 Problems

troxel

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Just got this monitor and was dead. Verified that 120 Vac was going into it, and it was.

Visually inspected it, and tested a few components. So far found that Q801 was bad and burnt, R812 was burnt but still tested good, C807 tested good, and D805 tested good.

I had one other pretty bad burnt mark on a leg of R801. How do I test this and what is it called if I need a replacement? I looked at the schematics and looked like R801 was two resistors, but didn't see the values of these. There are three leads coming off of R801, so I would imagine you can find the resistance between the two of the three legs and repeat. Is this right? Any other common failures not mentioned on Ken's guide?

I attached a picture of R801. (This isn't a picture of the chassis I am working on).
Thanks!
Theron
 

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Just got this monitor and was dead. Verified that 120 Vac was going into it, and it was.

Visually inspected it, and tested a few components. So far found that Q801 was bad and burnt, R812 was burnt but still tested good, C807 tested good, and D805 tested good.

I had one other pretty bad burnt mark on a leg of R801. How do I test this and what is it called if I need a replacement? I looked at the schematics and looked like R801 was two resistors, but didn't see the values of these. There are three leads coming off of R801, so I would imagine you can find the resistance between the two of the three legs and repeat. Is this right? Any other common failures not mentioned on Ken's guide?

I attached a picture of R801. (This isn't a picture of the chassis I am working on).
Thanks!
Theron

Replace IC802 Strs6707 along with Q801
Good Luck!
 
How can I test the PTC and where do I find a replacement if it's bad? Thanks for the help.
 
If it's a PTC, they usually measure close to a short, then increase resistance as they heat up.

If you know the value, you could check some of the suppliers like Mouser or Digikey.

I don't usually see them go bad, though. Certain models usually have cold solder issues with them...
 
If the PTC in question is in the degaussing circuit, you can take it out and it will in no way affect the operation of the monitor. The current flows through it on start-up to de-magnetize the monitor to improve picture quality, but only for a very brief time. I don't think I have ever seen one go bad in 30 years of fixing monitors.
 
I seem to recall one of the 7X00 series monitors having the wrong caps in the power supply section. I also think that 7300's had issues with their flybacks.

I dont recall what caps were wrong though.
 
How can I test the PTC and where do I find a replacement if it's bad? Thanks for the help.


The degausser circuit won't cause the set not to turn on.
From my experience with that chassis
You have no Drive for the power supply.
the transistor and ic need to be replaced and those diodes if bad
Also need to replace the caps for that circuit or a whole cap kit.
 
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