Another Predicta thread
 

Hi guys,

I've finally had more time to finish restoring a couple of 17 inch Predictas I brought into Australia.

They're almost finished, and the metal gold parts are at the electroplaters. I have them connected to a DVD player with NTSC out, via an NTSC RF modulator. Analogue TV went off ages ago. Powered by a 110V step down isolation transformer (on a 50Hz supply, not 60Hz) and have sound and picture on both of them after the usual recapping etc.



The problem on both TVs is that the picture bounces vertically a bit. Not rolling, it's as though the picture is wobbling on some jelly (jello?) I can't imagine that it's my mains frequency because the vertical oscillator still runs at 60Hz and all incoming power gets converted to DC anyway. The flicker is a bit like the old airport CRT flight schedules, where the text moved back and fourth rythmically.

If anyone has seen this or can point me in the right direction, I'd really appreciate it! The pictures are watchable, but it's slightly annoying.

Also, I'm after the original Philco manuals for the 17 inch Princess or Debutante and the Holiday (my next project) if anyone could please email them to me, or let me know where to find them. The SAMS manuals are great, but it's nice to have both. I luckily found a few pages on Google, but it's not complete.

Cheers and thanks for reading,

Adam

a video of the problem would help.

Sounds like 50hz ripple on the B+ supply, beating against the 60hz sweep rate.

Thanks for that,

I can post a link to a video I'll shoot today. I checked for ripple on the three main DC outs, the 275V, the 255V and the 160V, I thought that may have been an issue too. But all is ok! I've replaced all the electros on both TVs, but as always, have to factor in new potentially faulty components. No such "luck" this time!

Cheers,

Adam :)

Good luck. I'm curious about your electroplating experience. My support arms are all pitted and I'm not sure how to go about restoring them.

Could be 50Hz leakage from a tube with a H-K short...

Video uploaded to Dropbox showing shaking of picture.
 

Hi guys,

I made my first ever web video, I've shared it via Dropbox...

https://www.dropbox.com/sh/wee08ac61if62wd/B6oX5LxF54

Low resolution, about 1.1MB.


Please let me know if you can't open it and I'll try Youtube.
Otherwise, you'll definitely see the shimmer I'm talking about.

I'll keep you all posted about the plating, it will take about 5-6 weeks I was told and cost approx A$300. This includes a lacquering process to protect it. I really hope it goes well, as the firm looked very disorganised! I'd be very upset if they lost anything as I can't easily replace those sorts of parts. They did take inventory though which is a good sign.

I gave them all the metal parts of 3 Predictas in all, a Holiday with roll away stand, the Princess and the Debutante. I couldn't get hold of the missing side end cap for the Princess, so I flattened out a beer bottle cap! Not quite the same, but better than nothing. I'll use a dab of silicone to attach it.

From the Princess, I also removed the aluminium bar the runs across the front grille, as it had pretty much returned to silver. I say this because not all companies will work with aluminium for some reason (low melting point?)

Cheers,

Adam :)

Hmmm... I think Iv'e swapped out all the tubes, but I can check anyway with some NOS tunes I have ready for just such an emergency...

Thanks for the tip!

glad you did a video, I would say that is not a HK or any hum related type problem. make sure the yoke pins are clean, the vert height pot is clean, I assume you have replaced the boost cap and all the film caps in the vert circuit.
vert lin pot and bypass cap. oh and let not forget the tube pins, nice and clean.

looks like there is a very subtle flux in the output (not freq) of the vert out tube. somewhat random looking, the last thing I would do is look at the integrators. Or just let it run and see if it clears up on its own.

for hum, ground problems,beat freq problems you would expect to see a very consistant and smooth movement that is precisely timed.

Weird that both sets have the same issue. Seems like it has to be related to either your power or video source :scratch2:

$300 is an awesome deal for three sets worth of plated parts. I hope it turns out well.

You can buy a CD with the Philco manuals on eBay:

http://www.ebay.com/itm/PDF-Scanned-...item3a8d9393dd

No affiliation.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

Hi Guys,

I've tried him, but he won't post to Australia. One thing I haven't yet asked him is if he will email the files or put them in a shared folder after I pay. I don't really need the disc as the files will end up on the ipad anyway.

All the caps in the vertical circuits have been replaced except the ceramics. I'm also wondering about the couplates, the vertical ones in particular. I'm thinking of building one and subbing it in to test.

The video source can be ruled out, as I used it on my first set without problems. I recently finished an HMV set that looks almost identical to a GE set that Bob was working on, I couldn't believe the similarity. Shown here with a frame of "Tarantula!"

If I don't get a solution to the jiggling, it'll be interesting to see if I still get it when restoring the Holiday. By the way, I've also tried direct video in straight to the 2nd det terminal of the sweep board... no difference sadly. Meanwhile, I'll try your suggestions. Forgot to add: I placed a 470mfd cap in parallel with the main 275V filter cap, also no change. There was no sizable ripple, but I thought I'd try it anyway.

Cheers,

Adam

Problem solved!
 

Well this is weird. I set the DVD player to NTSC, thinking that would be the most logical. When I set it to PAL, it started rolling like crazy which I expected. But when I adjusted the vertical hold to fix it, I noticed there was no more picture shaking! Now it's as solid as a rock! :D:D

I'm very grateful for all your replies, I'll keep you posted on the plating.

I was originally quoted twice that amount by another company, who, as it turns out, don't plate hollow objects or aluminium. (Wish they'd told me that after I sent numerous pictures to them!)

I'm so happy to have two Predictas working, I'm probably the only one on Australia who does! Can we make it three??

On a different note, is the Sylvania Duelette a hard TV to come by? I'd love to add one of these to the collection.

Cheers and thanks again,

Adam :)

I was going to suggest that any transformer inside or near the set would be a cause of this.

One idea: order a small sine-wave inverter from the net, that runs 60hz and power it off a DC power supply running from the 220V mains. The cheaper inverters run quasi-sine which would introduce bars from the harmonic distortion on the power wave form, so avoid these.

Hi Adam. My daughter works at MV and lives in Rosanna, VIC. I do come to Australia at least twice a year. Next time, maybe I could bring CD/DVDs over with me. Just a thought.

It would be nice to see a Predicta in Melbourne!

Cheers Mate