Sony KV32S22 - half-way back from the dead - what now?

My 1997 vintage KV32S22 died completely during the final moments of the AFC playoff game last month. After reading this group and a bunch of googles, I decided to give repair a chance. A few minutes with a meter showed the common failure mode of a shorted HOT (Q502) that killed the PS choppers (Q601 &Q602) and the fusible resistor (R607). I replaced the failed transistors with quality OEMs and R607 with a Sony OEM. I removed, cleaned, and resoldered the HDT. The set now powers up, responds to the remote (on/off, channel up/down, volume, mute, etc.), and provides sound but no picture. The standby blinks at a constant rate which I understand means a bus problem or IK issue. Since the remote functions, I'm assuming the issue is IK.

I don't have an Oscope but I'd like to continue down a repair path. If the IK issue is due to a bad tube (common on the 32" sets like mine) I guess it means a new TV. Any easy way to test this? If not, what do I check next? Any "most likely" part replacement for this condition?

Mike

Reply to
J. Michael Milner
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if the picture was ok before the set died, then why do you think the tube is suddenly to blame? I dont think that is likely. This could be a missing voltage ( open resistor?) somewhere in or near the power supply. did you move the crt neckboard? are all cables in the right position after reassembly?

-B..

Reply to
b

When you power the set on , do you hear the HV come up ( Static rush)

Are the filaments lighting on the CRT?

The only time CRT failures are common on these is when the set has alot of hours on it.....like for the folks who leave it in all day long!

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Jeff Stielau
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Reply to
Shoreline Electronics

AFC

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I didn't see the picture tube as the set died (turned away during a commercial or time-out) but the picture was OK up to then. The tube being the initial source of the failure is just a guess based on what I've summarized from google searches - 32" tubes seem to be a weak link for this vintage of Sony TVs. Since the tube isn't a quick or cheap fix, I'd like to rule it in or out before investing more in the repair process.

I did remove the crt neckboard as well as the anode cap to free the A board from the chassis so I could get it to my workbench to do the parts replacement. I've double-checked all the wire harness connections but I'll triple-check again.

I see where the G board can be tested in isolation on this model so I'll first check all the resistors and then see what the voltages are (one hand in pocket).

Any other suggestions?

Mike

Reply to
J. Michael Milner

I pretty sure I hear the HV static rush (as sure as my aging ears allow).

Don't see any filament lighting. Do these come up right away when set is powered on? Would they be shut down immediately due to the error (constant blinking standby led)? Maybe I've lost one of the G board output voltages. Time to read the CTV-24 manual?

I'm not a big TV viewer, certainly not of the all-day variety. I don't use it for a night light either. Hopefully the tube has a few thousand more hours of useful life.

Mike

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guess

Reply to
J. Michael Milner

Do you have a voltmeter? Measure the collector B+ on the Horizontal Output. Careful! 130VDC and 1100V AC on there!

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Jeff Stielau
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Reply to
Shoreline Electronics

Output.

I have an HP 971A DMM that is rated to 1000V Ac and DC. Are you saying that the collector of the HOT is at 1100V AC or 130V DC (or 1100V AC riding on

130V DC bias?).

I also have poor man's scope - a Tektronics 2510 multichannel waveform analyzer - basically a very primitive multichannel data logger. It is limited to +-100V AC and the sample rate is very low (maybe 50ksps).

I've also got a copy of the Sony training manual for the AA-2/BA-3 chassis. Sadly my EE degree is 25 years older than the TV in question, so it may not help much.

Mike

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Reply to
J. Michael Milner

There is 1100VAC riding on the 130VDC.

Your meter should be OK for the task

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Jeff Stielau
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Reply to
Shoreline Electronics

I would NOT try to measure the C of the HOT with a DMM. Those HV AC spikes will damage many DMMs. It also might be possible for the capacitance of the meter to damage the TV. If you have HV, there's no need to measure this voltage.

If the heaters aren't lighting, but you have HV, then there must be an open in the heater circuit. It's a simple circuit that goes from a winding on the flyback to the CRT through a couple of resistors. There should be two pins on the CRT socket labeled "H". There should be low resistance between these two pins on the socket with the CRT unplugged. The same pins on the CRT should also have low resistance between them (a few ohms at most). You can also try measuring the voltage between the two heater pins on the CRT board. Use a DMM in AC volts mode. The number won't be meaningful unless you have a true RMS meter, but it should be several volts. If you do have a true RMS meter, it should be 6.3 V. Andy Cuffe

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Reply to
Andy Cuffe

In looking further at the A board, I find a 3 position lever switch labeled "H-CENT-SW" (S501) about 1/2 way between Q501 and Q502 (E1 area). The switch is currently in the center position. I can't seem to find mention of this switch in the service manual (aside from the parts list) or the training course (CTV-24 AA2). What does this switch do in each of the three positions? What is the normal (in service, non-test, etc.) position? I'd be very happy to find all I need to do to finish my repair job is set this to the correct position, as I may have disturbed it when removing the A board to replace Q502.

AFC

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Reply to
J. Michael Milner

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