Magnavox 32" TV HV randomly shuts off.
model MS3250C321
chassis A27951 (I think)
TV randomly shuts off the high voltage. Time between shutting off can be any where from minutes to hours. I have done a visual and can see nothing out of the ordinary. I have have a full schematic.
Searching this site offered no help. Searching the WEB found nothing conclusive, but there was talk of the Verticle IC (TDA8359J) possibly being defective.
Before I yank out a perfectly good part, can anyone offer some insight to this problem.
regards
Jerry, when you say HI voltage cuts out, do you get a line across the screen or is there no picture with sound or without sound?
Larry,
What happens is:
Click, like a relay de-energizes.
Picture tube goes black, no lines, no squares no nothing.
Sound dead.
Power on light still lights.
Turn off. Turn on and picture and sound returns.
Sounds like a bad connection in the sweep section or the sweep power supply. Also a posibility of a bad connection in the main power supply. Without some sort of measurments it is very hard to tell. Are you tech savey? Do you know or have any solid state circuit knowledge? Do you know how to use and do you have a multi-meter?
Larry,
I am an electronic tech with a semiconductor manufacturer. I have a scope, and an analog multimeter.
I tried flexing the board a little but that made no difference. I of course cleaned out all the dust, carefully.
One final thing about the symptoms. After it shuts down, the power on stays light, then after a few minutes, the power on light goes off.
What are you thinking?
Your going to need the service manual to check if the set is going in overvoltage shutdown from the power supply or possibly x-ray protect from a problem in the high voltage regulation. Once this is established, we can concentrat on the individual circuits. You can get a downloadable copy from http://www.samswebsite.com/photofact/...
I have this, the available online schematic. Is that what you are referring to?
Manual
Available
Available
On-line
You have it already? Well send a copy this way and we can proceed. send to [email protected]
Shot it to you.
In the last couple days, I have been hearing, on and off, that high frequency whine. It comes and goes but does not seem to be related to the shutdown problem. Flyback bad?
Check if you have 150 to 165v at the hot .
No that whine could be a bad power supply regulator. Let me look at the schematic and I will get back to you tonight or tomorrow sometime.
Oh I remember this Maggy. I found a few notes on this chassis. Check and monitor pin 3 on the flyback(T75445) for 130vdc. If right before the set goes out, the voltage starts to flutter and go up and down, there is a fault in the power supply. I found in there, several capacitors are leaky in value. An ESR meter will help you find those very quickly. I found a ESR project online somewhere that I built. It has been working fine for years. i used to repair tons of those mini camcorders with it. There are also some connection problems in the chopper stage of the main power supply. If the voltage did not flutter or change before shutdown, unplug the TV set and feel how hot the HOT(horizontal output transistor)is. If it is really hot, check the mounting bolt or screw, have found them lose in the past, or there could be bad capacitors on the secondary side of the fly, or the sweep power supply. I have also found bad connections in the horiz. drive as well as the horiz. oscillator circuit. Good luck. Let us know if you find anything.
Thanks Larry, I'll get on it as soon as I get a chance. I will post results.
Something new has been discovered.
When the HV shuts off, doing the following will bring it bacK: Using the remote control, or TV front panel, press CH+ or CH- (one time) then press CH+ or CH- again.
Example: Press CH+ and there is a loud click like a relay, the picture stays black. Press CH- and HV and picture returns.
Does this change your thinking Larry?
Hello, I am NOT technically savvy but I have the exact same problem with the same model TV. My son has offered (after only a little convincing) to help me IF we can find out what is wrong with the TV and IF it is worth the cost to fix it. Since it is a 2003 model that was probable obsolete by 2004, I know it probably isn't worth taking to a repair shop. My concerns are twofold and related to the relative value of the set itself. I cannot afford a modern type TV right now and a replacement of the same type as this one would cost around $400. My questions are: Although I don't mind paying $27 for the manual you mention, is the TV worth investing in it PLUS any parts that may be needed? And would the service manual be understandable to a semi-technical person? Are the tests and repairs that you are discussing something that would be within the scope of a person who has some technical experience but is not an expert? Thanks
For me, fixing it is not worth the time, trouble, expense, frustration, waiting etc. I aplogize to Larry for not following through. I was hoping for a quick fix. Although I am capable of the task, given enough time and effort, it just ain't worth it.
This link will get you the PDF version of the schematic. THe full up paper version may offer more information, but will offer no troubleshooting hints for the problem.
http://www.home.earthlink.net/~godrane/MS3250C321.pdf
good luck
PS: the TV has actually been behaving itself lately, it can go for days and shut down only a couple of times. Such is the black magic
Thank you for your reply. Your comments saved me the frustration of trying to figure out whether or not to even attempt getting it repaired.