Advice on diagnosing a D1626HT Sony 21inch CRT Monitor...

[JVene]

Hello all!

I'm no expert with CRT devices, but I do know electronics (mostly audio linear circuits and computers).

I have a Sony D1626HT Monitor (21inch, very nice item BTW) - it's a Dell rebadge.

I also happened to find a complete service manual (full schematics, board layouts, 50 pages - virtually everything required about the monitor).

I may have damaged the unit myself with an idiot's mistake. I ran the monitor at 100hz refresh at 1280 by 960 resolution (one of the non-standard resolutions of my computer) for a few months. I never noticed that the filter to 'exclude rates not supported' was turned off (a computer setting, in case that's not clear).

This means that I was running horizontal rates at about 128Khz, but now that I have the manual I see the monitor's upper limit is 107Khz. It ran fine for a few months.

One day I turned it on, and there's severe pincushion distortion. The image is still clear and bright, but the hourglass shape is very classic of a pin amp circuit failure.

Since it's digitally controlled, there's a postage stamp sized IC with 48 pins, surface mount soldered, which converts the onboard CPU's instructions into (I assume) analogue signals which are fed to the rest of the circuitry. I have high hopes this is not the device that's failed. It's part is CXA2043Q (Deflection processor).

My hope is that one or more of the transistors in the 'pin amp' or 'pin drive' section is at fault, or related components.

I'm asking for any advice you might have in tracing down what's up here. Unfortunately I don't have a scope, just a digital VOM.

Minimally equipped as such, can I verify that the CXA2043Q is sending out it's pincushion signal?

I can forward the schematics (I got them free online myself).

Also, the manual has a chart of the expected voltages for each transistor I can see in the 'pin drive' or 'pin amp' sections - can I expect to discover which section has failed with a VOM alone?

Also, I'm not exactly certain of all the description meanings here. The CXA2043Q has a pin labeled FBPIN, which is the closest I see matching a 'pincushion' signal. Other's are more clear, like HCENT, HSIZE, HSHAPEBAL, etc.

I've had this monitor for only a few months. It was a 'trash item' from a local company that 'upgraded' to all LCD flat panels, but frankly this 21" is so clear and crisp it's better than most LCD's on convergence and clarity alone (and much better on color) - probably the finest 21" I've ever seen. It would be a shame to trash the monitor over what I think should be a simple problem.

I'd take it to a shop, but my son is in chemo for Leukemia (doing well, it's the type they can actually cure) - but that makes the bench charge too much to swallow for at least another year.

I've designed sensor devices using analogue IC's, built audio power amps, mixers, computer controlled light dimmers - so it seems I should be able to replace a transistor - or even that microscopically soldered CXA2043Q, if I can keep my hands steady enough for 48 pins (once out, once in with the replacement).

Any advice would be most appreciated.

Thanks

[Weazel]

id put chip info into datasheet arcihive excusse mi lack of spelling and to make a scope id get a high freqincy transformer eg switchmode power supply and make a adjustable frequncy gen now if u get a crumy tv u disconect the verticle and horzontal coil the vert would hook into ur freq gen as ur time base and ur horzontal to ur transformer as ur voltage mesuring ull need to add mre but i hope u get the idea the transformer basicaly chances the low volatage to high reversing the input output as a computer psu puts 250/115v in gets 12v ish out since yoke coils need round ur mains voltage to run on data sheet they give u chips info this is there ideal cct for sed chip and this gives u wat ur scematic dont have using this ull learn how it all works and if ur chip is dead and u got lots time to waste i mean lots u could program a pic axe and make ur own cct to replace chip hope this helps

[jts1957]

Hope he's still in need of advice - after 3 and a half years.
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[Weazel]

never know these things have a habit of staying in ur workshop fo many a decade be4 they move on by medaling females =P