Trying to fix my 19-in Sanyo CRT TV

[Benyamin39]

Hi everyone,

My 19-in CRT TV is not functioning anymore. It is a Sanyo DS1904 dated 2005. It has the click click click syndrome on power on. The TV clicks , the tube start to light up, but then shutdown quickly, and then click again, the tube light up a bit more, and then shutdown, ...

I left a quick video to illustrate what happens.

I have the service manual (with PCB, components, ...). I have checked all capacitors on the board but they seem all ok. I have spent hours on it and reached a dead end. I hope someone can provide some guidance as I don't want to throw it away. I read it could be the flywheel to replace or a HV shutdown, but I don't know from where.

I am not totally newbie on CRT TV as I have modded another TV for RGB input, and read quite a lot about CRTs, but this click issue is tough. Hope someone can spot on the issue.

Thx!

link to my video on the clicking sound of my TV
https://imgur.com/a/HBY7eFs

[zeno]

Interesting symptoms. Almost looks like HVSD but usually that
will kill the set & latch it off until power reset.
1) post just the schematic.
2) check for cold solder joints especially the horz out & flyback area.
3) look for an electrolytic cap associated with the ON/OFF relay coil
power supply.

Odds are it should be an easy fix but take your time & stay on track.

73 Zeno
LFOD !

[Ed in Tx]

Originally Posted by Benyamin39

... I have checked all capacitors on the board but they seem all ok...

How did you check the capacitors?

[JohnCT]

Originally Posted by Benyamin39

It is a Sanyo DS1904 dated 2005.

Are you sure about that model? I recall Sanyos having 5 numbers, not 4.

When you say the tube starts to light, is the raster full? Some Sanyos will back out if there's no vertical deflection. If the raster is only a line or very short vertically, look for a bad vert output IC and associated caps and the B+ (low ohm resistor and rectifier off flyback).

Your video doesn't play.

John

[zeno]

John
It has most vert sweep. Raster pulses on & off Looks like everything is almost
there. Like a relay chatter or a run voltage off the FBT isnt coming up.
Also has a strange bright blob at bottom center.

73 Zeno

Originally Posted by JohnCT

Are you sure about that model? I recall Sanyos having 5 numbers, not 4.

When you say the tube starts to light, is the raster full? Some Sanyos will back out if there's no vertical deflection. If the raster is only a line or very short vertically, look for a bad vert output IC and associated caps and the B+ (low ohm resistor and rectifier off flyback).

Your video doesn't play.

John

[JohnCT]

Originally Posted by zeno

John
It has most vert sweep. Raster pulses on & off Looks like everything is almost
there. Like a relay chatter or a run voltage off the FBT isnt coming up.
Also has a strange bright blob at bottom center.

73 Zeno

Thanks.

I'm at home on my old XP machine - somewhere circa 2004 or so. Doesn't always cooperate with flash and other formats anymore now that most of them have been updated. Firefox is the last browser that still works (sort of). Time to build a new one but in all the time I've had this computer, I haven't had one blue screen or any other kind of hardware failure. I spent a lot of money on top end parts. But I guess it's time . Next one will be some sort of Linux build.

I'll look at the video tomorrow on my shop computer. I still think his model number is short a digit.

John

[Benyamin39]

Originally Posted by zeno

Interesting symptoms. Almost looks like HVSD but usually that
will kill the set & latch it off until power reset.
1) post just the schematic.
2) check for cold solder joints especially the horz out & flyback area.
3) look for an electrolytic cap associated with the ON/OFF relay coil
power supply.

Odds are it should be an easy fix but take your time & stay on track.

73 Zeno
LFOD !

Hi Zeno and thanks for all the responses posted on this thread so far. I have hope to fix it.

First, the TV is Sanyo DS19204, I missed one digit there.

1) Here-below is the schematic

2)
The first time I checked the capacitors, I checked all of them on the 120V sections and then everywhere else. I used my multimeter in ohmeter mode to detect a change in resistance. All electrolytic capacitors were ok but I will double check. I will look for the flyback area. For the ON/OFF relay coil power supply I can't locate it on the PCB at the moment. There is a power regulator (IC601), would that be what I am looking for?

reopening the TV now.

General Schematic
https://imgur.com/a/3t6izQ7

Detailed schematic
https://imgur.com/a/Mq7LEg5

Where I looked mainly for capacitors (120V area)

[JohnCT]

Originally Posted by Benyamin39

)
The first time I checked the capacitors, I checked all of them on the 120V sections and then everywhere else. I used my multimeter in ohmeter mode to detect a change in resistance.

You can't check capacitors that way. The only thing you can conclude from an ohmmeter test is that the leads are still internally attached to the cap's film/foil and the cap isn't *completely* inert. Here's what the ohmmeter test won't provide:

Capacitance value
Equivalent Series Resistance
Leakage
Dielectric Absorption

John

[Ed in Tx]

Originally Posted by JohnCT

You can't check capacitors that way....
Equivalent Series Resistance

Or "ESR". You need an ESR meter and study up on how to use one. It's pretty simple really. Capacitors dry out and the internal resistance goes up. Easy to measure in-circuit (with the power OFF). I'd almost bet money you would find the culprit electrolytic with one.

[JohnCT]

Originally Posted by Benyamin39

There is a power regulator (IC601), would that be what I am looking for?

That isn't really a power regulator IC despite what the schematic says. That is a precision voltage reference feedback IC that feeds the opto coupler.

The first thing to check is capacitor C609 in the primary circuit. Also, get a magnifying glass and bright light and look for any circular solder cracks on the transformer pins.

John

[Benyamin39]

Originally Posted by Ed in Tx

Or "ESR". You need an ESR meter and study up on how to use one. It's pretty simple really. Capacitors dry out and the internal resistance goes up. Easy to measure in-circuit (with the power OFF). I'd almost bet money you would find the culprit electrolytic with one.

Thx. I was initially inclined to get better multimeter with capacitance reading, but after doing a bit of research on your recommendations on ESR, I definitely need to buy one of these devices. It looks like there is no alternative to it for in-circuit checking of capacitors.

Not totally sure which one to pick though. the most expensive one is dedicated to capacitors while the cheaper models can test other components such as transistors. Anyway, I will pull the trigger on one of those.

https://www.amazon.ca/Multi-function...1027176&sr=8-7


https://www.amazon.ca/Multi-function...s%2C183&sr=8-5

https://www.amazon.ca/KKmoon-Capacit...1021626&sr=8-5

[Benyamin39]

Originally Posted by JohnCT

That isn't really a power regulator IC despite what the schematic says. That is a precision voltage reference feedback IC that feeds the opto coupler.

The first thing to check is capacitor C609 in the primary circuit. Also, get a magnifying glass and bright light and look for any circular solder cracks on the transformer pins.

John

Thx. I need to have get the ESR. Using the ohmmeter on 2000k, I can only see that the resistance rises steadily (but slowly at 4kohm per second). I checked also the solder cracks on the Transformer (T601 I believe). Overall the PCB solders look neat (at least compared to a 1990 JVC TV that I opened recently, for which there were also wild solderings done there back then; had I known I would have been more careful on the brand to purchase). After all the Sanyo TV is only 15 years old.

I will keep investigating once I got the ESR. Hopefully it is an electrolytic capacitor.

[AlanInSitges]

We used to see Sanyos that had bad Zeners that would cause this problem but I can't remember where they were. I think it's D001 in this schematic but not 100%.

[Benyamin39]

Hi,

I finally found the problem with my TV. It was indeed the RGB modding I was preparing between the OSD and Jungle Chip. Although at that stage I had only tapped 3 to 4 open ended wires in different places, I may have shorted 2 adjacent circuit board lines on one of the soldering point. I soon as I removed all the wires, the TV was working fine again.

Because of the symptoms, I was misled that this was a 120V or HV side problem, and I didn't think the low voltage circuit would be able to create such issue. But thinking about it maybe I touch to some power of signal or Sync signal?

Thx for everyone's help and I learnt quite a bit of useful info about capacitors and how to test them. I am modding this TV now and the first results are encouraging.