National VP-5220A Repair Help Please.

[Demonstar]

First off, sorry about all the double and triple posts. I've justmade another interesting find. Thee is a red wire and a black wire coming from the vertical preamp board to the main board. I swapped these around because they appeared to be back to front to me. Something odd then happened. The oppositte set of resistors on the main board got hot. I'm now assuming it's a problem on the vertical preamp board. I think I'm gradually getting there.

[cogil]

The glow on base of crt should be a propf of crt ok, and also getting the 5-9v which must have a source from supply unit.
If the supply
If the supply is on and the filaments not lighting then you should measure the crt heaters for a reasonable resistance like 2 to 6 ohms.
Otherwise locate from base plugging, one side to ground and the other with a 6v supply. If the filament is gone then your time on is not worth it.
Though they hardly go, if not gone then by tracing that 6v disappearance you might just get what fault there is for the other voltages.
even if a long try, the experience will last you a life time, best was to get a diagram or consult with your nearest technical or electronics tech, do you have the ht or eht to tube. and how about your +ve to horiz transistor.
Does the circuitry employ a Line Output transformer. remember this area cannot be ordinary meter measured when functional apart from the Danger.

[cogil]

sorry the third or so line should read;

If the supply is on and the filaments not lighting

[Demonstar]

Thanks Cogil!

I don't have glow on the CRT at the moment. I know very little about circuits involving CRTs so I couldn't follow all of your last post. How do I know what the pinout of the CRT is? eg how do I tell which are the heater pins?

I have only tested for the 12Volt supply on the power supply board and the main board. They are the only voltages I have tested for. Because of what I mentioned earlier I am expecting to find a fault on the vertical preamp board. I have yet to start looking there. I guess I need to find out whats going on with the heaters first. I just don't know what the jobs off all the wires going to the CRT are. I guess if I know which pins the heater is I can apply the correct voltage to them to test it to see if it glows then hunt for why the power isn't getting to it if it's still O.K.

I didn't know what you meant by a line output transformer so I searched and I think you might be referring to a flyback transformer??? I know there is a mains transformer but in the HV section there is a little silver box about 1 inch long by one inch wide and half an inch deep. I think that could be what you mean.

I'm really sorry for my lack of knowledge, I really appreciate your help! Thank you! I will get there in the end and will have learnt a lot along the way. Even if it never works, I have learnt a lot. but hey... It will work!!!

[Demonstar]

Would pictures help? I could try and get some if they would.

[cogil]

Yes close up pictures of the board components would help, and even of crt base would help. thats cause we have no manual at all.
if 5 pins crt the heaters are 1 and 5, but dont try power on this unless proved.
for 8 pins its 4and 5. but thats an old idea we had dont use unless proven correct.

[Demonstar]

I've uploaded some images. I'm really sorry for the poor quality. Click on the full size button to see a bigger image. I can take any more images needed but these should give an over view and get us started. The camera doesn't have a close-up mode so I had to take them where it would focus. They are 10 megapixels though so zooming shouldn't be an issue. If you download them and zoom you should be able to pick out detail. Downloading them as opposed to keep viewing them over and over online will also mean they don't get taken offline due to exceeding the maximum monthly bandwidth I'm allowed. Thanks much appreciated.

I'm going out to keep trying to fix the thing.

[Demonstar]

Here's the link to the photos (REMOVE ALL NUMBERS FROM THE URL. DON't LEAVE ANY WHAT SO EVER! It's the only way for me as a guest to post a web address. I can't link it because it keeps saying something about spam.) Sorry for the inconvenience!

w54254w3w.fx434grimoire43524524.w5845ebs.co43m/app43243s/phot54os/

[cogil]

[Demonstar]

Thank you very much! It is much appreciated!