Predicta has raster, sound, but no picture

[wcarroll]

Looks like height and lin controls are misadjusted.

Readjusted the height and vert. lin. pots. Things look much better now. Also cleaned the tuner and the tube sockets. This helped with the overall performance of the set.

The picture still "rolls"... If I adjust the vertical control, it will stop rolling for a few seconds, but always continues to roll. Is this a problem typically caused in the vertical output section?

Getting ready to order some orange drops... Looks like a real pain to change the caps on the pc board. A previous tech soldered most of them to the leads of the original caps. I can see why he did this! It's nearly impossible to get to many areas on the pc board from underneath!

[jpdylon]

You need to desolder all the leads from the board, as well as the tabs holding the board to the chassis, and remove the board to service it properly.

There is a website from a member here I believe that has good detailed pictures on his philco restoration. Definitely worth the read:

http://antiqueradio.org/philc12.htm

[Charlie]

Once you go thru the caps (and also check the resistors) in the verticle section, you'll fix that roll. If memory serves, there's probably one of those damn combination-components in the verticle section. It's a tan rectangular flat piece with several leads on it... it's made up of several caps/resistors. Those usually go south. Sams will give you a schematic of it on the main diagram page. If you get the caps and resistors, and follow the schematic, you can build one to replace the original. Just gotta make sure you follow the diagram carefully. Make sure you number the leads that come off the end result so that you'll plug 'em in the right spots. I've built a few for some of my sets with really good results. It's just a little time consuming.

[Phil Nelson]

Yes, that's my Predicta restoration article referenced above. It describes removing the board. It also has a little discussion of replacing one of the couplates ("those damn combination-components"). My homebrew replacement isn't gorgeous, but it was easy to make and works fine.

[wcarroll]

Well, I went ahead and replaced the four capacitors in the vertical section as recommended by Don and others. Also checked the two resistors mentioned and they test within spec. Can't see that it made any difference. I may have to build the K5 couplate next... I suppose the rest of the main board caps should be changed first.

But, another problem has started which has been getting progressively worse. Periodically the set will lose all horizontal output momentarily.... The picture collapses and then immediately starts to come back. When this happens, I hear a "click" sound from the high-voltage cage, presumably from the flyback transformer. I've tried watching carefully when this happens, but can't see any arcing, just the the "click". Started out only happening once or twice in a troubleshooting session, but now it is about every 15-30 seconds.

Does this sound like a flyback problem?

Thanks for all of the suggestions so far, I really appreciate it!

Wes

[Don Lindsly]

I have some NOS couplates. Do you have a part number?

Don

[Phil Nelson]

Yes, I would bite the bullet and replace the remaining caps on that board. As long as the board is out, you might as well rebuild the couplate, unless you can reliably confirm that all its components are good.

Re the spark, I would check any/all other little components in that cage -- resistor, cap, etc. I don't recall offhand what's in there, but there might be something.

Reason I mention that is that I'm working on an RCA 630TS which had a burned resistor underneath the little phenolic board holding the 1B3GT tube in the h-v cage. More or less impossible to spot the spark, even in a dark room, but after I replaced that resistor, the Bzzt went away.

You probably know this, but I would not run the set for long periods until you find and fix the Bzzt source :-)

[wcarroll]

I have some NOS couplates. Do you have a part number?

Don, The part number for the K5 couplate is "30-6509-1". Please also check to see if you have K4, which is the "vertical integrator". It is Philco part number "30-6030-7". Thanks!

I would check any/all other little components in that cage -- resistor, cap, etc.

Phil, I am going to attempt to do this... It is going to be a real pain to get into the high voltage cage. It looks to be as unserviceable as the rest of the set!

[Phil Nelson]

Not to be a wet blanket, but I thought the capacitors inside those couplates were paper -- which might mean that a NOS couplate would be as bad as the one you're replacing. If there's any way to check those caps with a capacitor tester under the right voltage before installing the couplate, that couldn't hurt.

Re the h-v cage, my Predicta is a barberpole and the stuff inside the cage is all quite accessible. Made doubly easy because the cage cover on my set is missing :-) Things may be different on your chassis. I have never worked on one of those.

[wcarroll]

Turned out to not be so bad getting into the HV cage. The black coating on the flyback is cracked and crumbling. There are several chunks of the coating missing from the bottom:



Would black RTV be OK to re-coat the flyback? Also found two resistors --- one of them under the horizontal rectifier socket as Phil predicted. The other can be seen in the picture above. I will replace them while in here. I don't really see anything else in here, except some dirt and dust that will clean up.

Also, I want to replace or repair the HV lead that runs to the picture tube. There is a previous "fix" to the insulation with some electric tape. I'm sure this tape isn't rated for high voltages... Any suggestions here?