Magnavox PTV730 6S4600 powers up partially (no pic no sound)

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ManyaCarb
Magnavox PTV730 6S4600 powers up partially (no pic no sound)

Hi everyone

Got this set a couple of weeks ago completely death. I noticed there was a power resistor rusted and the copper on the pcb area cut due to probably a short. So I fixed the copper trace and wanted to make sure that the power transistors were ok.

Well I found that the two big ones ( 2SD1556 ) were short between collector and emitter (probably due to the short). I replaced with some that I had around (BU508). After that the set came back to life but the image was very poor. I noticed that the blue CRT coolant and the green CRT coolant were really bad. About 15 minutes of warming up I noticed a leak on the blue CRT. I shutted it off and cleaned it up. I also replaced the coolant with new one from MCM and the diaphragm that was worn.

The set came back to life for the second time, much better now, but with the convergence problems. So due to I don't have the original remote, I tried to align the tabs for convergence using the color bar pattern that a local station is transmitting. I got the blue aligned much better, but the letters were blurry and hard to read.

So I managed to go to the convergence menu with a universal remote using the code I got in one of the threads, but there s no way I get the crosshairs aligned. Apparently there s something wrong or perhaps the remote doesn't help much

After turning off, I tried again with a different color bar from a DVD but nothing. Then, the set didn't come on again :(  . It just gets the heaters on the tubes and the green led in front of the set but nothing else. Couldn't get the manual for this particular set, however  I checked a similar one for the PTV770 series that helped me a lot. But still I can't get the picture back. I read there are 4 power supplies and the logic IC controls the power for the high tension.

Any suggestions on how to troubleshoot these? kind of hard to do it with a multimeter on the floor close to the HV's wires....I appreciate any help in advance

Have a nice day, Al

ManyaCarb
Quick update on this issue.

Quick update on this issue.
I just downloaded one of the service manuals posted on the Downloads section on this site for the PTV 770 series and I saw that is pretty similar to the set I have.
I did reset the values to "factory defaults" as stated in the service manual, turn it off, then back on and the set came back to life again.
Not that bad for an old set like this one.
Thank you very much to Mr. Dillon who posted all the Magnavox manuals and shared with the community ;)

evil
Larry is no longer with us

Larry is no longer with us

http://www.techlore.com/forum/thread/30723/Farewell-Larry/

Congratulations on the repair.

 

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