Predicta Tandem restoration
 

A couple weeks ago I found another Predicta Tandem set locally for a reasonable price :banana:

Unlike my other Tandem set, this one has a good cable. Also all the knobs, back and the antenna!

Now for the bad. When the sets former owner moved back to Chicago from Texas, a fire broke out inside the moving truck :tears: Some of his other sets were a total loss, but this one didn't look too bad. I think it's all superficial.

Also he said it had been restored and working back in Texas, but it wasn't anymore :scratch2:
http://farm6.staticflickr.com/5276/7...1dcdaf5a_c.jpg

http://farm8.staticflickr.com/7127/7...331a3cd2_z.jpg http://farm6.staticflickr.com/5339/7...4da14eb6_z.jpg

I hope this gunk will buff out.
http://farm8.staticflickr.com/7247/7...27b80ba2_z.jpg

The chassis is all sticky and stinky, but looks to be in good shape.
A few caps have been replaced from the topside. I found more repairs underneath.
Both the fusible resistor and thermistor are intact. They have both exploded in my other Predicta sets.

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Wow, 2 of those! They are rare enough. That cable looks better than your other one before you cleaned it. Can't wait for the video! Hope the CRT tests good.

It sure does :banana: Good life test too.
Better yet it's a 21FDP4A aftermarket replacement that's superior to the failure prone original.
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The chassis is cleaning up well with naptha paint thinner.
On top of the goo from the fire the sets former owner is a heavy smoker. It has quite a delightful aroma :yuck:
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I found a loose wire and broken resistor lead on the contrast control. I wonder if that's what caused the set to stop working ?

http://farm6.staticflickr.com/5236/7...71217e08_z.jpg http://farm9.staticflickr.com/8148/7...717713fb_z.jpg

Only one way to find out :D
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I used a 150W bulb in series and slowly brought it up on a variac. Just a little crackle from the speaker.
http://farm9.staticflickr.com/8158/7...198e18b5_z.jpg


I plugged the set directly in and was treated to some sporadic flashes of light on the CRT accompanied by arcing sounds. I checked inside the flyback cage but didn't see any arcing.
Next, I wiggled the tubes and the arcing clear up.
Here's the first stable raster.
http://farm8.staticflickr.com/7270/7...6e318c9a_z.jpg

I hooked up an antenna and was able to pick up a local LP station on channel six but no sound.
http://farm8.staticflickr.com/7264/7...75da76a2_z.jpg

Then I hooked it up to cable. More tube wiggling and I have sound :music:
It's weak though and I have a lot of horizontal tearing.
Not bad for a first power up :yes:
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Ah that lovely smokey barbeque flavor :D

SR

Hi Bob, I corrected your typo in the title. :yes:

I saw your video on this set and I can only imagine how it smells!

I think I would take the 409 and a garden hose to this chassis, otherwise you're going to have to live with it every time it gets warm!

Thanks! I was going to ask, but you beat me to it ;)


Good idea. Yes, it sure does stink when the set warms up.

Here's a link to the video I shot while working on the set: http://youtu.be/qQLT7X1erbg

The screen is funky - especially at the bottom left. Perhaps it's from the fire ?
It also has a faint aroma of vomit so typical of this type of plastic (tenite?) :yuck:
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Novus #2 had no effect on the haze, but #3 plus a lot of rubbing did the trick.
http://farm8.staticflickr.com/7268/7...35e85b16_z.jpg http://farm6.staticflickr.com/5200/7...de03c5be_z.jpg

There are a few scratches that perhaps could be wet sanded out.
http://farm9.staticflickr.com/8010/7...47d408e2_z.jpg http://farm6.staticflickr.com/5337/7...8a0f4200_z.jpg

The screens seem to be very receptive to buffing out.
I stole the one from my Holiday to put on the Pedestal set, I had to do a bit of buffing on it too. I used a headlight buffing kit, started at 800 grit and went to 3000 followed by rubbing compound and then polish. It looks good but it seems impossible to get all of the fine swirl marks out, they aren't visible when watching it so I guess it doesn't matter.

My biggest complaint is the green-ness of the screen cover, almost Hoffman like.
I like the picture when viewed directly off the tube but putting the cover on muddies it up.

I agree about the greenish tint. The later Sietsa and Princess sets have clear covers. I think it's a different type of plastic as there's no stink
http://farm3.staticflickr.com/2669/4...41468ff8_z.jpg

I feel the same way with the color roundies, the shaded non glare safety glass has the same effect. The early ones have clear plate glass and some of the later ones have a clear non bonded lens. The clear ones seem more bright and you tend to keep the brightness a little lower.

Now as for the cabinet, it has some damage from the fire. It's darkened in areas and there's a big stain on top. Also one side seems to have gotten wet which caused the masonite bottom to swell and push the veneer out a bit.
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I started out with some Howards RAF mahogany and 0000 steel wool. Later I switch to GoJo hand cleaner.
I really should have gone with the Gojo from the beginning to try dissolving the crud off rather than steel wool.
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I fixed some veneer separation too.
Next, I used some 400 grit sandpaper to smooth out the worst of the aligatoring and applied a couple coats of lacquer sanding sealer.
http://farm8.staticflickr.com/7131/7...66d6e431_z.jpg

Despite the superficial fire damage, it looks like you got a very nice restorable Predicta.... I know exactly how that thing will be smelling right now! :yes: When ever you 'fire' it up in future it will fill your apartment with the aroma of charcoaled BBQ cigarette smoke! Maybe stick it out on your back porch for a month! :D LOL Cheers Glen

Can't wait to see this done. Not sure if there is much need to have it perfect. I'm sorta fond of that "survivor" look if it's not really "broken" looking. Some sets are just BEGGING to tell you a story. It's nice that you DO have the story behind this set's survival.

Found this AD for the Predicta Tandem.

Matt

Cool, thanks. I'll be diving into this chassis soon now that my Holiday is working.

So there was success with the remade K Networks?

Now that I've gained some experience from restoring a Holiday set, I've begun work in earnest on this set.

Here are some closeups of the old repairs.
http://farm9.staticflickr.com/8460/8...e3578f51_c.jpg

I would have clipped out the old resistor.
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The thermistor has been replaced. I'd better check it.
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The schematic calls for a 30-6519-1 network, but I found a 30-6519-2. The difference being the value of resistance between points 2 and 6.
Maybe they ran out back at the factory and added the external resistor to compensate :scratch2:
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I though I'd use my other, all original, tandem chassis to guide me in the restoration but it turns out they are slightly different.
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http://farm9.staticflickr.com/8199/8...377a0f13_c.jpg

One obvious difference is the height of the flyback cage and color of the big socket. More importantly, I've found some component and wiring differences so I'll have to be careful.
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I wasn't really happy with the cabinet so I decided to strip it. That will also give me the opportunity to fix a few issues like the swollen side and bottom.

The cabinet is held together by screws and comes apart fairly easily.
http://farm8.staticflickr.com/7130/8...93f10b17_c.jpg

I stripped the legs and used Mohawk red mahogany toner on them followed by semi-gloss lacquer. I think they turned out real nice.
http://farm8.staticflickr.com/7277/8...57bfdac2_c.jpg

I've stripped the main body and managed to steam out most of the dings :)
http://farm9.staticflickr.com/8210/8...ae4c5b23_c.jpg

If the cabinet turns out as well as the legs, you've got it made! :))

Thanks, we shall see.

I wasn't able to steam out all the marks. I think because it's more of a scratch or gouge and the wood is just gone. So I'm trying an old trick I learned on "This Old House".
I made some mahogany sawdust using scrap veneer and a little saw. Then dabbed a little glue into the scratch and sprinkled the sawdust on. Once the glue sets up, I'll sand it smooth.
http://farm9.staticflickr.com/8204/8...eac84352_c.jpg

Good luck, I must remember that trick myself!

Will the scratch still stand out against the photofinish when it's done? Even if it does, I suppose it's a lot better than nothing. (Or perhaps you could use a very light veneer as your source of shavings then fill in the grain with a selection of brown textas to recreate the photofinish)

I'll be interested to see the final result! :)

Oh, this isn't a photofinish like on the Holiday. This is all real solid and veneer mahogany. If the damage had been really bad, I would have just re-veneered the whole top. Next, I'll seal the wood, fill the grain and use the same red mahogany toner lacquer I used on the legs.

I'm making steady progress on the chassis despite the dubious old repairs and production run differences.
Currently, I'm down in the horizontal output tube corner where I encountered some corrosion.
http://farm9.staticflickr.com/8065/8...7220fd4f_z.jpg

The rust was easy enough to dissolve, but the socket has seen better days. It's an octal and snaps into the chassis with no fasteners.
Does anyone know where I can get a replacement :scratch2:
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I'd be going after that smoke damaged chassis with some 409 and hot water.

I've washed quite a few chassis now with soap and water and so far it hasn't hurt any of them, things like paper Filter covers and labels have to be removed first but most everything else is metal, plastic or coated with Shellac.

This place has some self-mount sockets like that but I've noticed in the past that there are several different chassis hole sizes so you'd have to check that well.

http://www.vacuumtubesinc.com/Produc...beSockets.aspx

Thanks for the tip. I've been using a similar product called Spray 9. It works as well or better than 409 and smells nicer :) Just like in my Holiday, the wires have gone all gooey from age. The Spray 9 works OK on that but paint thinner is even better.

Thanks. I see they have a few other items I need for other projects too :thmbsp:

I suggested 409 because it was the only commonly available cleaner I could think of that's worth a darn.
We use something at work from Ascot Supply called Purple Cleaner, similar to 409 in that it's Purple, but in undiluted form it'll dissolve Bakelite and strip paint! (don't ask how I know that :sigh:) Anyway it's great for cleaning chassis, Chassi, Chassis's... (what is the plural of chassis BTW?)

I'd seen Lee (M3-SRT8) touting the virtues of Spray 9 in his restoration threads, but it seemed to only be available on the East coast. Until a few months ago that is when I found it selling in 1 Gal. bulk containers for just a few bucks at a local Home Depot.

Apparently chassis is the plural of chassis ;) http://www.merriam-webster.com/dictionary/chassis

The topside was pretty grungy too, but I'm slowly making progress cleaning it.
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Also, the cabinet is ready for some grain filler.
http://farm9.staticflickr.com/8485/8...ecbb115f_z.jpg

I filled the grain with some Constantines red mahogany grain filler. After it dried, I lightly sanded the cabinet and sealed with Deft lacquer sanding sealer.
I managed to get a couple light coats of Mohawk cherry/red mahogany toner lacquer on the cabinet before the temperature dropped 40F Thursday night :sigh:
It might be a while before I can put on some coats of clear and rub out the finish.
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I'll keep plugging away at the electronics in the meantime.
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Looking good as usual! I think that there are very few original components on that PC board! Should work like new or even better.

Thanks for sharing the progress.

Fantastic job so far! That cabinet is really looking the part.

It's interesting to see the board, I notice that all the components are either parallel or perpendicular to each other. One thing I generally notice about vintage boards is that components just seem to be randomly scattered at crazy angles. Even my Princess and Debutante boards (same thing) are not neatly arranged like your board shown here, yet they were produced by the same company at much the same time. Weird...

Right you are. Funny, I never noticed that before. Here's the main board from my Princess set with the crazy angles (and plenty of dust).
http://farm4.staticflickr.com/3659/3...6e5250bf_b.jpg

Bob: I'm finishing up my restore of a tandem and I'm trying to figure out how to remove the back of the case from the crt so I can replace the caps, etc. I haven't found any info on a strategy. Have you worked out what to do on this yet?

Sure. I'll take the case apart like I did with my Holiday set. http://www.videokarma.org/showthread...255328&page=10

The procedure is outlined in the Sams service info. Basically, remove the decorative brass plate, unhook the spring holding the plastic trim and remove the steel strip holding the case halves together.

Thanks for the info. I thought it would be a different procedure than the princess, etc., but you're right, it's the same. Came apart very easily and all old caps are gone. Best regards.

I just got this mahogany base unit from a fellow collector. No legs, no cable, no CRT.

I think I'll use this chassis too as it's relatively rust free. Looks to be 100% original components except for the tubes.

http://farm9.staticflickr.com/8536/8...0d4b0f6d_c.jpg

Assuming the paint comes off, all it needs is a little touching up :)
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Unfortunately, the antenna was bent and just barely hanging on. One little flex and it just broke off :(
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