K7000, Good B+ but no high voltage

Oryk Zinyo

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I have a 19" K7000 chassis that I received in a non-working state. I found the HOT was blown and since it still had the old fly I replaced it, as well as installing new caps. Now the chassis will not power up.

I have a B+ of 122.5v. Removing D10 did not allow the monitor to power up. I am hoping for some ideas besides the flyback (rings good), since I am out of replacements at the moment...
 
This is strange. Do you have a high voltage probe?....is the high voltage zero?...or just really low?

I'd check to see if the B+ voltage is actually getting to the flyback....maybe a cracked trace.

Edward
 
Can you get raster lines by turning the screen control up on the flyback? If not, I'd swap back in the old fly and see what happens.
 
Don't put the old fly back in. Check for b+ on the tab of the hot. If you have a scope verify the 15k at the base of the hot, and the transformer.
 
I am not putting the old fly back in.

I can hear a fain click when powering it up, so I may just have a really low high voltage. My HV proble is not with me at the moment but I will grab it and check tomorrow. I have already checked all of the traces and they look, and test good.
 
Update: This is fixed.


I powered up this chassis today and forgot it was on. After about 30 minutes of operation the monitor came up in a faint horizontal collapse. Turning up the screen adjustment barely affected the brightness. I began searching the horizontal output section for problems and found that the cathode of D18 was loose. Someone had completely lifted the trace and soldered the leg to the old landing but it was not in the circuit. I checked surrounding components and C36 was found to be shorted. Replaced C36 and jumpered D18 back into the circuit and now I have a good working 19" K7000.
 
I am bumping this thread because I experienced something similar on a differnet chassis:

25" K7000 chassis. I receive it with no HOT and signs that the fly has been arcing.


Installed cap kit, HOT, VR (found to be partially shorted), and powered up the chassis. After a few seconds it blows the fuse, however B+ was spot on at 130.2vdc. Began further testing and found yet another shorted C38. I am currently out of these so parts are on order. I will update the thread after I get the chassis operational...
 
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