Predicta Pedestal Restoration begins.

[Don Lindsly]

1. Temporarily disconnect pin 4 of the 12DQ6, HOT. That will save the tube while troubleshooting other circuits.

2. The hor freq coil is a two terminal device. It is possible it is open. Short it out with a clip lead. The circuit will run without it, but will be unstable.

3. If you then get -45 volts on 12DQ6, pin 5, then reconnect the screen voltage and look for a picture. Bring it into sync using the hor frequency adjustment. It is usually mounted near or the rear part of the hold control.

4. If the coil is open, carefully remove it and look for a broken wire from the coil to a terminal lug. Otherwise, look for a replacement coil.

[Eric H]

Hi Don, tried what you said and jumped the coil, that brought back the high voltage so the coil must be open, possibly I nicked one of the wires while working on the board and can fix it, if not I have a spare chassis though I hate to start taking parts off of it.

I have a junk Philco Seventeener, i wonder if it uses the same coil?

Other issues noted, a very scratchy Horiz Hold Pot, possibly an open Height Pot since it jumps from a 3" band to full height at a certain point, tearing in the picture suggesting it needs Filters and it's very unstable in both directions.

[marty59]

Wow! But you've got it making a picture that's great! I have those pesky scan lines at the top of my raster too no matter what the source is...

My Linearity Pot would open up at certain spots and create all kinds of havoc, and I had to dedicate a pot mounted elsewhere to correct it. The contrast portion has completely opened up so I've got to get creative with that one also. What is it with Predicta's and their controls?

Once you've gone through the vertical and if you're having problems getting the height and Lin correct it may be the 10DE7 tube. They can check good and one may not be like the other in circuit. It's good to have a few and check for best results. I've got a couple good extra pulls just PM me if you need 'em.

[Tom Albrecht]

delete - didn't see the second page!

[Don Lindsly]

Eric:

There are a few portables designated Seventeener. It depends on the year. Another coil will work, however you may need to change the capacitor across the coil. Make sure the replacement coil mounts correctly since two of the three terminals are shorted together on the PC board.

Let us know the chassis or model number of the donor set and I will let you know the correct capacitor value.

Try some spray cleaner in the frequency and hold pots once you get the new coil in place.

Don

[Tim]

Eric:

If the Philco part number is 32-4754-3, I have a NOS one I can send you. PM me with your address.

[Eric H]

Tim, P.M. Sent.

[Eric H]

Having a little free time I unsoldered the PC board and removed the coil, Sure enough it was wide open.

I could see the inner and outer windings were connected to the lugs, the inner winding is inaccessible beyond poking it to see if it was solid (it was) so I unwound a turn on the outside to see if I could find the break, I snapped the wire after about a turn but there was no evidence of an easily accessible break, verdict, the coil is shot and it was that way to start with (i.e. I didn't break it)

Tim has graciously offered me a new one so this project will wait until it arrives, maybe I can get in some cabinet work in the mean time.

[DaveWM]

Eric, have you considered engineering in a removable board? I have thought about that, using keyed connectors for the PCB and adding ground connectors so you can maybe work perhaps a screw method for attaching the PCB to the chassis. I know its not original, but something I would prob do if I had a hard to work on chassis. I have a princess, I would consider doing something like that if I have had to pull the chassis in the 1st place.

[Eric H]

Dave, I have thought about that.
It wouldn't be hard at all, get about four or five 5 pin connectors with pigtails and attach them to the pins on the board, and the mating connectors spliced to the wires on the chassis, or if one was really ambitious run the wires all the way back to the point of origin and do away with the splices.

Not original but then again neither are the 30 or so new caps I installed.
Plus every time you unsolder the wires they get uglier and uglier, not too good for the board either.

[DaveWM]

there is a product I have used in the past for keyed wiring, anderson power poles, they are easy to install, and can be ganged together in a way that keys them. would be real easy just cut the existing wire, crimp or solder on and move on down to the next. after attaching them you slide them together to form a group (can be as many as you want).

http://www.andersonpower.com/product...onnectors.html

clearly overkill current wise, but easy to use.

[Eric H]

Well hot diggity dog! it works.

I got the coil for Tim today, got home and slapped it in and tacked the board back down, didn't want to secure it completely until I know it's done for good.

Fire it up and it works, got HV and I am able to get the Horizontal to lock in, sort of.
Actually the sync was still really poor in both the vertical and horizontal, I tried another 9BR7 Sync tube, still no good, not only poor sync but a big black bar in the middle of the picture and it's squirming around like a bucket full of worms.

Thought maybe it was a bad filter so I jumped them all one at a time, it didn't make the slightest difference.

OK, what's left, bad tube maybe? I had tested all the tubes on the PC board and replaced all the sweep tubes but I never got around to checking the three tubes on the IF strip, I started tapping them with a screwdriver to see if it affected anything, it did, the picture flickered, but even worse, the 5AM8 would light up really bright for a moment.
It did this a few times and then the set faded to black and went off, OK I burned out the 5AM8 because it had a Heater to Cathode short, that's good news.

What wasn't so good was it somehow must have sent a surge through the 12DQ6 HO tube because now it wouldn't light either, this is the second 12DQ6 I've burned out in this set!

To wrap it up I took all the IF tubes and the 12DQ6 from my Holiday set, they are almost all new anyway, put them in this set and fired it up, (slowly), now it has a nice sharp stable picture!
All that sync trouble was caused by a H-K short in the IF tube, if I had only checked them also I would have saved some time.

I decided to try a 17DQ6 output tube, I figured it couldn't hurt to lower the heater string voltage by another 5 volts, (it was already modified to use a 6.3 volt CRT, whatever that entails), the set works just fine with the higher voltage DQ6 and it may be a little easier on the tubes this way. My line voltage is usually around 124 volts anyway.

I still have to hook up a speaker and check the sound, hopefully no problems there. Also the Vertical Height (or Lin) control does have an open track so I can't get the vertical adjusted just right, I may try to fix it or just add a pot inside since it's hidden anyway.

Here's another picture.

[Don Lindsly]

A 17DQ6 is a 450 ma filament vs a 600 ma filament for a 12DQ6. That means the 17DQ6 is running with about 25 volts on its filament. Measure and verify it. It will work, but it won't last long. The models that used a 17DQ6 had an entire 450 ma string.

The filament string has a surge limiting thermistor to prolong tube and diode life. While not 2012 technology, it was not bad for the time.

[Eric H]

Hi Don, I thought they had the same ma rating, oh well, I 'll change it back, thanks for the alert.

I put in a new Thermistor, the fusible resistor was bad however so it's running without that for now.

Did a little more tinkering, centering the picture, adjusting the Yoke and it looks fantastic!

I had to replace the 3BN6, it was weak and so was the sound, I had to do just a little tweaking on the coils and now it has great sound too.

[Don Lindsly]

Eric:

I have a few NOS fusible resistors laying around somewhere. I will let you know.

Don