Thanks, I'll reserve judgment on the vertical until I replace the K7 couplate.

I discovered that there's (barely) enough room to sneak a soldering iron under the board and unsolder the couplate leads without pulling the board. Tomorrow, I'll make the replacement and give it a whirl.

Regards,

Phil Nelson

If you have to deal with tough bugs in both deflection circuits, and if they are both on the same (tough to remove) board then it might be a good idea to mod it so all the wires going to the board are numbered quick connects to facilitate checks during trouble shooting.

on mine I was able to get at a lot of the caps with a soldering GUN with the tip bent 90 degrees. The problems I had with the predictas were the bent wires (not through hole plated) so its easy to mess up the traces if you are not very careful. I used a lot of solder wick (coated with flux) to get everything cleaned out. Also low power on the dual heat gun. I dont recall if there was enough opening near the couplates for the bent gun tip trick.

I always thought the output from the plate of the horz osc was a sine wave, that was modified by a RC network (the couplate in this case) that made it look like the correct Hor output tube grid drive. Guess what I am getting at is to make sure you are getting the correct wave from from the horz osc. of course if the couplate is goofed up maybe that is not possible. It sure seems like the couplate has to be the problem if all the voltages are correct at the horz osc tube.

Well, I removed the couplate last night and I had to cut it up to remove it, since the access is very tight and a couple of the leads were bent. It's hard enough to remove one of those long, multiple-lead jobbies all in one piece when you have normal access.

As I recall, voltages on the 6CG7 were normal except the negative voltage on its grid was deficient or absent, similar to the HOT. Yesterday I did check that 6CG7 socket carefully, confirming that the resistance is normal on each pin and that every pin actually connects to the right spots. I also pushed things around and didn't see any evidence of an intermittent pin or broken trace.

I'm not confident that I can install a new couplate in this cramped space without messing up a trace underneath. Whether the TV will need further work at this stage is unknown. Adding quick disconnects on all of the board leads seems worth a try. Then I can swap the board in and out faster and less destructively. This local place has small Molex connectors:

http://shop.vetcosurplus.com/catalog...oducts_id=6845

I already connected three of the six ground stakes with a bus. If I complete the bus to connect all six of them, then I can use one Molex to connect the bus to a ground outside the board and perhaps reduce problems with bad board grounds.

Some of the leads from the board will need lengthening. I'm going to leave the existing wrapped/soldered connections alone and cut each lead an inch or so from the board to install the disconnect.

This will take a while. My hand-drawn diagram lists about three dozen leads, plus the six ground connections. After drawing that diagram, I got a copy of the Philco service manual, which has a nice diagram labeling everything on the board. I'll use their numbering scheme this time around.

Phil Nelson

I like the idea of leaving the WW alone and cutting about 1" away, then attaching the connectors, doing 1 at a time and if possible some way to color code or number. If I ever work on another predicta that requires any kind of tough dog work (like a busted socket) then that is how I would go. I like sermos connectors (aka anderson power poles) because I have used them in the past for RC airplane use (my other hobby).

Thanks for the connector suggestion :yes: I'm about to dive into my first predicta and have been searching around for connectors. I had no idea what they were called though and was coming up empty.

The Molex connectors are bigger than I expected, once I got one installed:

http://antiqueradio.org/art/temp/MolexConnector.jpg

I bought 10 of those today, all the store had in stock. Maybe I'll go back there (or a hobby store) tomorrow and look for power pole connectors. I built an RC plane some years ago and do remember those connectors being smaller.

The Philco manual has a diagram that labels the connection points and tells what they connect to. This snippet shows WW connectors L38 and L46, etc., as well as ground connector G16:

http://antiqueradio.org/art/temp/BoardDiagram.jpg

I'm a little concerned about creating a mess of wires & connectors hanging over the board. The factory installation tucks the leads along and under the board edges. Things may get weird by the time you have three dozen connectors up above, leaving enough slack to unplug & plug things without accidentally snapping leads off the WW pins.

Edit: The powerpole connectors look about the same size as the Molex, 1-2/3 inch long when complete. They also appear to be the crimp-on type, which I like less than soldered connectors.

http://www.mouser.com/catalog/specsh...heet-42848.pdf

Phil Nelson

Well, I came home with a sack of powerpole connectors, which are even thicker than the Molex type.

http://antiqueradio.org/art/temp/Pow...Connectors.jpg

The parts store had nothing smaller. The only alternative was spade-type connectors, which are just too danged ugly.

I'm starting to wonder if this is a bad idea . . . .

Phil Nelson

maybe stagger cutting so they dont line up, I can see how its going to get kinda messy with a lot of connectors, considering the space limits. You need to do a lot of planning before making the 1st cut.

Yah, I'll stagger them for sure. For some of the WW pins, I may remove the old lead and install a new one made of more flexible multi-stranded wire. That will be the short pigtail to which the other long end connects.

Maybe I'll sit down and draw a diagram, as a way of thinking through the whole layout wire by wire.

Phil Nelson

yep. maybe even just tape them in place to see how its all going to work out. This looks like one of those deals where you really want it all figured out before starting. Of course if it does work out, I am sure there will be a lot of predicta owners that would follow your approach.

Would something like Molex female terminals pressed right onto the ends of each board pin work?

I just tried out a Molex female terminal, and the answer is yes. The size is right and it fits pretty securely.

The Molex terminal doesn't go down the full length of the pin, but I compared it to the factory video lead, which plugs onto the board the same way, and that connector only covers about half the pin, too. The video connector is simply a female terminal about the same size with a bit of shrink wrap around it.

The question is whether you would want to trust all three dozen leads to that sort of junction. Philco used that type for the video lead, so it's not completely loony. On the other hand, this board is dodgy under the best of circumstances.

You'd need to extend a number of the leads a bit, to accomodate this kind of connector. That would be less work than installing two-piece connectors all around, though.

If you did use push-on connectors all around, there would be some risk of accidentally dislodging one when replacing a tube, etc.

Phil Nelson

Ugh. The powerpole connectors look too big. I laid out several next to the terminals where they'll connect:

http://antiqueradio.org/art/temp/PowerpoleTrial.jpg

Picture each one of those with a 1-2 inch pigtail to the board and a longer lead trailing above or alongside. Seems like a real mess to me.

By loosening the ground stakes and dismounting the rear pots and range switch, I was able to lift the board a bit, perhaps enough to install the couplate. If that works, I'll reconnect the grounds and see what happens.

Phil Nelson