D9410 horizontal issue after repair

[lilshawn]

I'm repairing a D9410 that had a mass failure in the SMPS and horizontal drive sections. I have replaced a number of components and have the chassis mostly running, but have an issue with the horizontal size being smashed down and not adjustable.


The unit was presenting with zero activity absolutely dead, and after replacing the SMPS drive mosfet and driver chip,(Q501, IC501) found a pile of horizontal deflection parts blown/shorted (D213, D211, Q207, Q206, ZD201)


The unit is now displaying an image that properly fills the screen vertically, but is only filling the screen center horizontally about 1/2 width. adjusting the H-size results in zero change.


I've been checking and rechecking resistors, capacitors, and diodes in the IC201 deflection IC processor outputs and inputs for the horizontal stages trying to find an issue but cannot find the source.


If you have any ideas where I might look next, any help would be greatly appreciated.

[itsdanik]

Is the image centered, or is it shifted?
I'm troubleshooting a similar problem in an MTC900/E ATM (width controls work, but position controls don't), and from what I gather, power delivery to the HOT can cause all sorts of horizontal deflection problems, so maybe you could check on that, too?

Also, check this nice guide for all sorts of CRT monitor troubleshooting tips

https://www.repairfaq.org/REPAIR/F_monfaq.html

[lilshawn]

yes, it's centered properly.

yeah normally i'd suspect some kind of open condition on the S correction capacitor circuit, but this particular chassis is all microprocessor controlled. I'm suspecting some kind of feedback is off.

seems like the V EW-DC bias voltage on the EWOut being higher narrows the width... need to find the cause.