Sanyo TV brightness issues

[mramos1]

I could not find a model number, will look again, but I have a Sanyo 27" flat glass CRT type TV.

For years I could see the re-trace lines a little in the picture if I got close to it. Now, I think the issue is coming to the front. I know TVs are cheap but if I can fit it, I like this old TV.

I think it is maybe 5-7 years old. Has 2 s-video and 2 RCA sets of inputs.

What it is doing, it will be fine then it will go bright white full screen for a bit and then flip back to normal. Hoping it is a simple cap somewhere and someone like Nigel has seen this before

Any ideas outside of a new TV. It is ashame the schematics will probably cost 1/2 of what a used TV will cost.

 

[Nigel Goodwin]

Check the voltages on the CRT base, the cathodes should be running about 150V or so, adjust the A1 control until they are.

 

[mramos1]

Check the voltages on the CRT base, the cathodes should be running about 150V or so, adjust the A1 control until they are.

Thanks Nigel, will do. Happy Holidays..

 

[audioguru]

I entered the model number of my Sony TV in Google and got many sites trying to sell its service manual but I found one link with a free one.
I also found a forum where guys talked about the same problem my TV had.

Yours is intermittent so a part has poor soldering or a connector needs to be re-seated.

 

[jumides]

here's a good site for you, search for chassis no.
https://www.eserviceinfo.com/chassis2model.php?firsttime=true

look for sub bright(bias),screen (bias),ABL capacitor it maybe defective.

 

[crusty]

It's probably your verticle output driver, usually a transistor, it's usually near the flyback(very careful bubba, keeps a couple 10K volts for a while unless discharged) it usually has a large heatsink also, although if you don't have a replacement or any info on the transistor than you're outta luck. Quickest fix would be to adjust the flyback if it does have any adjustments, usually there's 2 adjustments, and upper and a lower. One should control contrast, and one should control voltage. Try turning both of them to see if there's any resolve to your situation, but like i said be careful not to touch the big red cable, or the rubber flap around the back of the tube.

 

[Nigel Goodwin]

It's probably your verticle output driver, usually a transistor, it's usually near the flyback(very careful bubba, keeps a couple 10K volts for a while unless discharged) it usually has a large heatsink also, although if you don't have a replacement or any info on the transistor than you're outta luck. Quickest fix would be to adjust the flyback if it does have any adjustments, usually there's 2 adjustments, and upper and a lower. One should control contrast, and one should control voltage. Try turning both of them to see if there's any resolve to your situation, but like i said be careful not to touch the big red cable, or the rubber flap around the back of the tube.

Ignore this load of complete rubbish! - and don't go randomly twiddling the focus or A1 controls!.

A little 'knowledge' is a dangerous thing!

 

[mramos1]

Ignore this load of complete rubbish! - and don't go randomly twiddling the focus or A1 controls!.

A little 'knowledge' is a dangerous thing!

I dropped the contrast and brightness from the TV menu and it works. Still see the retrace lines like when I first received it.

Will do the 150volt off the CRT after the holidays. Hope A1 is labeled.

I would hope all on this forum that have electronics background (at least at my age) know about the high voltage on the anode. I recall color TV at 30K+ went I went to school, maybe technology has them down to 10K now.
But either way thanks for the warning.

Thanks again for the help. Kids spent all the money and Dad needs a TV.

 

[crusty]

Ignore this load of complete rubbish! - and don't go randomly twiddling the focus or A1 controls!.

A little 'knowledge' is a dangerous thing!

It ain't like you're going to blow it up turning them down or up all the way! Sometimes experimentation makes for a quick fix....or a broken product. I have never shorted out anything adjusting these, besides getting a slight jolt here and there. Most times this is a quick cure, if it doesn't help anything, which i'm sure it will, then put them back into the stock positions.

 

[crusty]

I dropped the contrast and brightness from the TV menu and it works. Still see the retrace lines like when I first received it.

Will do the 150volt off the CRT after the holidays. Hope A1 is labeled.

I would hope all on this forum that have electronics background (at least at my age) know about the high voltage on the anode. I recall color TV at 30K+ went I went to school, maybe technology has them down to 10K now.
But either way thanks for the warning.

Thanks again for the help. Kids spent all the money and Dad needs a TV.

i say a couple 10k's , i've seen them everywhere from 8K-80K for the gigantic monstrous tubes.

 

[Krumlink]

No, the flybacks usually stay in the 35kV range. Asked a 30+ TV repair guy myself. I picked a Flyback about the size of my head, it output about 25kV with my driver.

 

[jumides]

hi mramos1,
A few question, so we can firgure out your tv problem.
what is color of the retrace line (red,green,blue,white) ?.

Very high brightness, produce white retrace line. you can adjust Screen control on the flyback (two pot are there screen and focus) , figure out which is screen (sometimes it was in CRT board). adjusting focus may cause arcing , AVOID Touching any metal/heating sink that is connected to ground/chassis/earth while adjusting focus/screen .

May I know "jungle IC and micro controller IC" number ? , coz There's a Pin controlling the brightness , which is some times(different model) connected to Sub Bright, which is also connected to ABL flyback (not directly connected but few resistor and transistor before ABL flyback), and connected to capacitor range about 0.1uf to 10uf . note : I'm not sure in the connection but it is common in different model/brand. take some sanyo tv schematic make it as your reference, look on Brightness,screen,ABL , (R,G,B,G1,G2 CRT board section) .

 

[mramos1]

The retrace lines are blue. I will probably attempt to open in Saturday as I do not see this getting better.

 

[jumides]

Adjust the Blue bias (Blue drive) on Crt board, check resistor/bjt on BK (blue cathode).

RED Video amplifier,Blue video Amplifier, Green video amplifier (crt section), it has the same circuit/component.

Make a comparison between component with the same value/voltage .

Download sanyo schematic any model(tv), use it as reference for voltage measurement on the crt board secton.

Yours is intermittent so a part has poor soldering or a connector needs to be re-seated.

yes, guru was right !! solder all components on crt board first, before any test/adjust to be done. .You may get an "Unbalance White" (white as white Paper on Screen). BIG!!!! TROUBLE on adjusting RGB Bias. Specially on moving object/changing color on the screen.