Sony shut down

Forgot to mention, I checked all diodes, resistors in the power supply. Not sure how to check the voltage regulator though. Thanks.

Also forgot to mention, this isn't a Sony. It's a Sanyo. Too many sets on the bench!. Thanks group.

Thanks for reply Jamie. The flyback does tick during start up, but I'm not sure if this is normal or not. I haven't tried ringing the windings or anything yet.

HV supply is bad? (FLyBack)? or maybe the HV-TRAnsistor?

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also, many units derive low voltage from the flyback when it's fired up. I have found in some cases where this voltage gets rectified, the filter caps are bad.. and other times, devices connected to this source are shorted.. the main PS unit also may monitor this source to know when to shut down the unit if voltage is gone or never gets there after a couple of sec's

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Thanks again. Iv'e checked every cap in the PS and all good. I'm sure the main PS isn't the problem. Iv'e also checked several other electrolytics, and nothing yet. Again, without a manual or schematic, I can only check each component as I go. This may be beyond my capability, but I'll reply after the flyback test - even though I was told by a tech this can give false results. Thanks again.

How do you know the HV starts up?

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I can hear it, and feel the static electricity build on the screen. But it doesn't stay up long enough to show any raster - only a sec. or two. Thanks for the reply. Any suggested checks much appreciated meat. You have helped me before.

Sounds like it could be going into X-Ray protection. It will do that if the HV goes to high if the tuning in the HV circuit is incorrect. I don't recall how old the set is but I used to work on plenty of them in the

80's and I doubt they got rid of that circuit. There are a couple caps in that circuit that provide tuning along with other devices. Sets that acted like this I would ramp up on a variable supply and monitor the voltage at the anode to troubleshoot it. That's about the extent of my help however right or wrong it turns out to be :)

Thanks Meat. Again, this is a SANYO. I f'd up in the original post saying it was a Sony. This set is only 3 years old. I agree that it may be a protection circuit shutting it down, and I do have a variable supply that I can try, and go from there. Thanks for the info.

You need a HV probe for the anode. Start it out around 60 volts and see if it fires. If not jump up 5 volts until you get it to start. Look at the HV, if it goes above 25KV it should shut down. Have fun and watch those lethal voltages. Let me know what you find. Watch the chassis too because most of them are above ground around 200 volts. Don't be brave :)

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OK, I managed to get the set to stay on around 70V on the variable. The high voltage stayed up but the flyback was still ticking. Anode checked 18KV and was stable. Set shut down around 80V on variable. Checked the raster while HV was up, and saw a faint glow in the middle of the set (about 1" square) that pulsed with the flyback ticking. If I vary the voltage below or above 70V, the relays in the PS start clicking like crazy. I suppose the flyback could be bad even though the HV is stable?

Unless there was a common problem with flybacks on this chassis I would not include it on my possible list. That's one problem I have being out of the loop and not knowing these things. When the set does shut down at 80 what was the HV? You might want to get your wallet out and snag some service literature and check some voltages. Also you could look for some cold solder joints in the SMPS and HV block/flyback before you spend money because I've read about issues with newer sets and lead-free solder.

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Thanks. I am now looking in the SMPS. Trying to find info on the switching IC to see if I can determine if it may be a problem. I already checked all componenets in this area. Haven't checked solder joints yet. BTW - the HV was steady 18KV when the set shut down.

Ok cool. I'm sure you'll find it.

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Shucks! I thought this was an announcement that Sony, USA had closed its doors...

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