These data were all taken with the set plugged in but not "on".
8V 0.60
V12 10.56
+Vsupply 0.01
For the transistors, all bases and emitters were 0V. Collector voltages were
TL031 10.53
33 10.52
35 131.7
61 0.1
62 0

 

8V 0.60

I don't understand this point. Shoooot ! got it. It's the 8V0S line giving 0V

V12 is OK..!

+VSUPPLY won't be there since set is not running.

Hmm.. This is getting some where..!

I believe u have a protect kicking in.

 

Need to probe the 8V reg.

See the schematics power supply page, bottom left, u will find teh Reg IP030, a 9pin chip on a heat sink.

First check pin 2 for the 10.56VDC u got for the V12 line before.

If pin 2 does not have voltage then check fuse FZP30.
If pin 2 has the voltage, pin 1 should also shud be the same.

Next check pin 4. This pin will be activated if the set is turned ON from standby. Other wise I think it would be 0V.
If the pin is held LOW then the regulator will shut down.
I believe when the pin goes to around 3.3V the Reg will give output,
@ pin 8, which is the 8V Vcc.

If things get confused around there, check pin 6. see whether it is LOW or HIGH. Not in between.

And u might need to check the fuses in the secondary of the transformer too. All of em.

 

Attached are the details of testing last night under the direction R!f@@, with me and my son-in-law providing eyes and hands for local testing.

After reviewing the details, I believe most of the results are valid and the wheels came off only at the very last step, #8 in the attached. No surprise - late at night is when mistakes are made. I suppose we must have mistaken the labels on a couple of jumpers. I will resolve this at the next opportunity, in the bright light of day, before continuing on to other tests.

View attachment Test results.zip

 

I've had to repair just about every TV that I've owned for various failures; GE, Motorola, Panasonic, Hitachi.

That hissing sound on older sets was typically caused by the internally shorted flyback.

DARWIN WARNING:
One thing that I was taught for testing the HV ouput, and have done on older units, is to put the tip of a screwdiver with a well-insulated handle under the plastic hood of the HV cable that goes to the CRT. If you get arcing to the tip then the HV is good (it is conducting through the high impedance screwdriver handle and you).

A less macho way of doing this is to remove the HV cable from the CRT, and tape it an inch or more away from some grounded metal with NOTHING else nearby -- briefly turn on the power.

The least macho way is to rent/buy an HV probe.

Oh, by the way, make sure you discharge the HV output before placing your fingers in the area.

An even less macho method,which only works if you have hairy forearms,is to rest your forearm against the screen & turn the TV on.

If the tube is being fed EHT,the hairs on your arms will be attracted to the screen.
If they touch the screen,the charge is equalised,so you have to take the arm away for a second then repeat,when,if all is well,they will again be attracted.

This is quite sensitive,as it will even detect the very brief presence of EHT generated when you turn on a TV where the horizontal output transistor has a short from C to E.

 

Wayn ! U did not list the V12 voltage.

No matter, Replace them CP094 & CP064. I believe they 1000μf. No ?

While u are at it. Check 'em all. That will make ur day.

 

U did not list the V12 voltage.

Nope. I carefully checked our chat log and we switched focus to the regulator immediately after I reported the 6V5 voltage, and you judged the µC to be working. V12 would have been our next target.

Will look at those caps ASAP.
Is there something in the data that makes you suspicious of them?

 

Yaaaaaaaaaaaaaa!

Low Voltage !!

Need to even the odds.

 

Low Voltage !!

Interesting. Way back in #45, I commented that "...I think I found 10.5 volts on "V12", which should be 11V or more. This makes me wonder about the optocoupler [IP001]..."

That measure of V12, which would have been taken with the set off but buzzing, matches up with the new data in the spreadsheet (row 10). I don't think it was taken while the power light was on, although I can't be sure. I didn't realize at that time that the set would go through 3 attempts to start up before stopping.

Anyway, should I still have an eye on that optocoupler or wait for testing/replacing those caps? If I have to order caps, I'll include the optocoupler either way. But I might have some caps on hand.

 

Just find some to rule out the low capacitance theory

 

Finally I have replaced CP064 and CP094, the two 1000µF electrolytic caps for the V12 and 6V5 supplies. I used new Panasonic low ESR 1200µF caps.

I also replaced IP001, the optocoupler that feeds back to the power supply.

Alas, no joy. The voltages on the two supplies come up to 10.58v and 7.05V with the set plugged in but power light off. With the power light on, these fall to 7.06 and 5.41. It's tough to get a steady number, as the set cycles off pretty quickly.

V12 appears to have a problem. A clue perhaps?

I can see already that I should have also replaced CL035, another 1000µF cap sitting on the V12 line in the deflection area.
[update] I used one of the old CP064 or CP094 1000µF, 25V caps to replace CL035, which is a 1000µF, 16v. No change. CL035, now removed, is not shorted or open and holds a charge.

 

Still the same way ?

 

Yup. Dead set. The only news is the "discovery" of the big drop in V12 at attempting power-on. The voltage on CL035 is briefly higher than CL064 at power-on but equilibrates just as the set cycles off.

 

Let me catch up..

 

I became suspicious of transformer LL033 (is it a choke?) but back in post #66 I noted that it gave a decent ring result on its primary, with my DIY tester. So the primary is not shorted or open. What else could be pulling V12 down? A problem with the supply itself, perhaps. I wonder if I could just inject a 12v power source instead of using the existing supply.

 

u could inject a 12V but it should be isolated, but be careful about the current capacity needed by the TV.

Remember to switch on the 12V immediately after the TV.

 

Looking at the circuit on post #14, can you remove the 3 fuses on the secondary side, and disconnect the output from the +126V, so the psu is working with no loads, (i know the opto wont have a 13V supply to work) but will it work then, or have you done this already?

 

Looking at the circuit on post #14, can you remove the 3 fuses on the secondary side, and disconnect the output from the +126V, so the psu is working with no loads...

That's a good idea.
In #26 I found that my Hout was likely shorted:
• Applying [external] 20V to JP065 - an easy-access jumper on the supply to the horizontal transistor - took my power supply down to under 1 volt at over 1A, maybe 2A. !!!!! That's very suspicious, right?

I confirmed this in #33; I reported seeing 132V on UB1 with the Hout transistor removed (it had failed to a short).

But I have not done the testing you just described. Since my problem appears to be with V12, I'm thinking of cutting jumper JP051 (easier than removing fuse FP061) first. I can check the voltage from the supply, as well as get an entry point for injecting external 12V.

 

... be careful about the current capacity needed by the TV.

This could be a problem. My little supply can't get over 2A. I may need a car battery or such. I'd feel better about full isolation with something that doesn't plug in anyway.

 

This could be a problem. My little supply can't get over 2A. I may need a car battery or such. I'd feel better about full isolation with something that doesn't plug in anyway.

Do not use a battery.!