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Sony KV-A2913E (chassis AE1C) auto shuts off after one minute

muygolfo69

New Member
I am wondering if someone could give a little advice about my
Sony KV2913E (chassis AE1C) that auto shuts off after one minute. Then I must disconnect it and connect again and the TV works without any problems (the TV turns on without stand-by).
Sometimes it auto shuts off once or twice. It happens always at the begining (or warming).
Thank you for reading this issue.
PS I am preparing a video of this matter to upload here. When I had it ready I will upload if its size is allowed.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Does the red light on the front flash, if so how many times? - and if it does, use google to find what the error code means.

However, google doesn't seem to find that model number, have you misspelt it?.

As a blind guess (based on decades of experience as a Sony engineer), it's probably the CRT that is worn out - the set may well be trying to compensate for the low emission tube, but it's too far gone and out of available range. In such cases increasing the first anode voltage (A1 control) slightly may give a few months more use out of the set. But generally, this type of failure shows an error code on the front LED.
 

muygolfo69

New Member
First of all, thanks for your fast reply and interest showed.
You are right, the exact model is KV-A2913E. I have just photographed and attached here its label.
Regarding blinking error codes, the front leds are off when the TV auto powers off. There is not any blinking from them.
The quality of image is amazing and that is the main reason why I am interested in repair this unit. Obviously I am not a expert in CRTs but I always have cared of brightness and contrast levels to avoid problems in this part of the TV.
I left the TV in stand-by this morning to test at night. By the way, when I was going to open it, I must remember to check the B+ voltage if it is OK
 

Attachments

  • KV-A2913E.JPG
    KV-A2913E.JPG
    1.6 MB · Views: 46

muygolfo69

New Member
Do you mean G2 as showed in the attachment?
I will check also R522 (100k) with the +B.
By the way, warming power supply running in stand-by around 8 hours had not better result.
 

Attachments

  • image_2021-08-22_224832.png
    image_2021-08-22_224832.png
    236.1 KB · Views: 50

Nigel Goodwin

Super Moderator
Most Helpful Member
Yes, the one labelled G2 - you might also check the voltages on the cathodes of the CRT - pins 8, 9 and 10. These will be affected by adjusting the G2 control.

In common with any relatively 'modern' set it has automatic grey scale, so as the CRT wears out it automatically turns itself UP - resulting in lower cathode voltages, until it's outside of it's adjustment rangem, when it then shuts down. By turning the G2 control up, this gives it more space to adjust in, and often gives a short term improvement.

Check the cathodes before you adjust the G2 - they should all be fairly similar, and about 150V was usually my 'go to' voltage reading. You will probably find that one of them is particularly low, and that would be the gun that's failing.
 

muygolfo69

New Member
Hi again,
Values before adjusting:
Stand by:
8. 135.x Vdc
9. 135.x Vdc
10. 135.x Vdc
G2:52.x Vdc
B+ 135.0 Vdc (same more than year adjusted)
With image:
G2: 452.0 Vdc (cold)
B+ 135.0 Vdc (same more than year adjusted)

After adjusting G2 (RV701 potentiometer turning rights slightly) up to 469.0 Vdc it seems that the problem has disappeared...:)
Stand by:
8. 135.x Vdc
9. 135.x Vdc
10. 135.x Vdc
G2: 58.3 Vdc
With image:
G2: 469.0 Vdc (cold) 465.x (warm)
B+ 136.9 Vdc

I´ll make another test later.
Thank you Nigel!
 

Nigel Goodwin

Super Moderator
Most Helpful Member
No point measuring the cathodes with the set in standby, you need to do it while it's running - and displaying a greyscale would be good, but not essential.

As I said originally, it's almost certainly the CRT worn out, and tweaking the G2 a bit higher will give you a little bit more life out of it.

I've seen this MANY, MANY times over the years - but not recently of course, following the total demise of CRT :D
 

muygolfo69

New Member
With image running after changes:
8. 124.5 Vdc
9. 119.x Vdc
10. 126.x Vdc
G2: 469.0 Vdc (cold) 465.x (warm)
B+ 136.9 Vdc

According values of scheme uploaded before they are good values, aren´t they?
 

Nigel Goodwin

Super Moderator
Most Helpful Member
With image running after changes:
8. 124.5 Vdc
9. 119.x Vdc
10. 126.x Vdc
G2: 469.0 Vdc (cold) 465.x (warm)
B+ 136.9 Vdc

According values of scheme uploaded before they are good values, aren´t they?
There's not really any 'good' values, they will vary with how it's set - to make the set brighter you take the cathodes lower, or the G2 higher - so as you adjust G2 the cathodes will automatically adjust themselves, the trick is to get it within the self adjusting range. Previously the set was shutting down because it was outside the range it compensate for. The cathodes are fairly similar though, and interestingly the weakest one is green - it's usually the red gun which wears most, as it's driven harder.

The service manual gives some crap about applying an external 175V to the cathodes or something silly - I've never been able to understand that, or to get it to work.

My 'goto method' was usually (on all sets - decided on after decades of setting thousands of sets) to adjust the G2 to give about 150V on the cathodes, then if needed 'tweak' from there. 150V generally gets any set going, if it's going to work at all.
 

muygolfo69

New Member
Hi There!
Yesterday Saturday the problem has happened for first time since Tuesday. This time, about 5 or 10 minutes after turning on the TV turned off itself. Only once.
Does anyone know which is the signal that is shutting down the TV in the attached schema? (In this pdf file you can search text in any pdf editor by Ctrl+F)
 

Attachments

  • chassis AE-1C KV-C2949D.desbloqueado.pdf
    622.2 KB · Views: 3

Nigel Goodwin

Super Moderator
Most Helpful Member
Hi There!
Yesterday Saturday the problem has happened for first time since Tuesday. This time, about 5 or 10 minutes after turning on the TV turned off itself. Only once.
Does anyone know which is the signal that is shutting down the TV in the attached schema? (In this pdf file you can search text in any pdf editor by Ctrl+F)

As I've already said, it's almost certainly the CRT low emission, and careful adjustment of the G2 control 'may' allow you to find a place where it will work for a while.

The circuit itself seems a bit unusual, having the SMPSU inside the same chip as line and frame oscillators, and I can't see the usual external trip components.

Try adjust the G2 for around 150V on the cathodes, and see how that works.
 

muygolfo69

New Member
No Sir.
I do not touch anything without knowledge. I never do it.
In fact, I will back to the G2 value 52 Vdc.
As I said at my first post, there is no stand-by when failure occurs. Then first and sound step will be check IC604 TEA7605 +5.1 Vdc.
 

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