So I picked up this TV and I get NO POWER LIGHT AT ALL. I am unable to get any trouble codes. I checked all the circuit boards for any CRT coolant and I found no signs of leakage anywhere. I also checked for any leaking capacitors and found none at all. I am suspecting a bad power supply. Has anybody come across this problem or know how to fix it?
Have you checked the glass fuse for the plug?
Yes I have along with all other fuses I could find.
I found R9A22 and I have voltage there.
R9A02 may come off the negative DC side of the rectifier I can't tell from the schematic. How did you test it, did you test each end of the resistor or did you use a ground and test the resistor one end at A time? CAUTION there are different grounds, hot and cold so if you use the wrong one you will do more damage than good.
I haven't tested the resistance of it yet. As far as testing for voltage I just connected one end of the resistor with one of the leads on my multimeter and I connected the other end with the other lead. I did this on R9A22 as well and I got ~60 volts going to that resistor. There are 0 volts on R9A02 however.
Bad news: I just discovered CRT coolant leaking from the green picture tube. Luckily it is very early in the process. A few drops got on the convergence board and I am currently cleaning it. I don't think the bad damage has happened as of now.
If you tested it like that and didn't get a reading it's most likely good then. With removing coolant the best thing you can use is denatured alcohol or rubbing alcohol will work fine.
Which board was the fluid on? From the front of the tv left middle or right board?
It is on the convergence board the one in the middle on the backside next to the convergence IC's. If I hadn't discovered this now then a few hours later the coolant would have gotten on the green board. It is very fortunate nothing is on the green board. I know it is delicate and is just about impossible to repair.
Do you know how to stop a coolant leak?
Replace the seals in it, I've heard of people using silicone. Is it coming from the fill plug or the top part where the focus lens is?
if it were me i'd worry about getting the tv running before putting money into it. you can drain just enough so that it wont leak but still provide a little cooling if it fires up while you are trouble shooting it.
Can you show me where this diode rectifier is? Looking at the schematic I think it's the little square labeled L9A02. Is this correct?
im using page 3-4 on 3-Power_supply it makes it easier for me to read. I think we can skip the rectifier all together and go straight to the secondary side,cold ground,of the transformer and see if we get power on the standby supply.
check for 12V and 5V on the stby supply.
I don't think we are on the same page here. Are you using the actual service manual? If not, what are you using?
when you download the manual there is a file called DOCS its the 3rd pdf in that file called 3-Power_Supply its the 3rd or 4th page.
to check the 12V stby voltage from Transformer T9A20 put the positive lead from meter on the positive pin of Diode D9A30 with the ground going to a cold ground or chassis ground,most metal heat sinks are cold grounds where you attach the coaxle cable the thing with threads in it is almost always a chassis ground the green -most of the time- wires that run from the boards of the crt to the outer casing(what you want)that has several connections for the green wires are usually cold ground. you have to use your meter and check for continuity between these and make sure you are using the right ground, if they all read infinate ground between each other then you can safely assume its ok to use either one.
before you power it back up make sure you have all the coolant off the board use caution as it is conductive.
I do get 12v from D9A30. What is next?
I get 5v on D9A33.
I looked in the parts list but no go, you are supposed to have 12 volts to that terminal from K9A50 though.
Have you found Anything labled K9A50? it may be a typical transformer with a connection "bus bar"-the difference
Yes. It's just a small black rectangular box.
you need to check for 12V supply on the the secondary side of it. if you trace the tracks on the board from resistor R9A02 to the K9A50 that is the primary side. The secondary side is the other set of terminals, the terminal you want is the one thats not connected by a track to a transistor. check that terminal for 12V
I checked it and I do get 12V. I'm assuming this is direct current since the polarities have the labels I've seen on DC circuits.
ok I found the transistor its a 2SC1740S-S - NPN pin-1 is emitter pin-2 is collector pin-3 is base you need to get a current/voltage reading from the collector pin I believe.
The pins on the transistor start with pin-1,emitter,on the far left looking at the flat side of the transistor.
To rule some things out you need to short pins emitter and collector on Q9A51, make sure you dont touch anything else but these pins.
no not voltage you need to short the two pins-connect them with a short piece of wire soldered to the board or attached to both legs or you may even be able do it with a screw driver.
What am I looking for here? right now the signal board is disconnected. Does it need to be connected?
I thought we were testing the power supply which involves the convergence board and the deflection board. Right now the two boards are sitting outside of the TV.
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