Predicta Tandem restoration

[mpatoray]

Found this AD for the Predicta Tandem.

Matt

[bandersen]

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

[mpatoray]

So there was success with the remade K Networks?

[bandersen]

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.


I would have clipped out the old resistor.


The thermistor has been replaced. I'd better check it.


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

[bandersen]

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.




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.

[bandersen]

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.


I stripped the legs and used Mohawk red mahogany toner on them followed by semi-gloss lacquer. I think they turned out real nice.


I've stripped the main body and managed to steam out most of the dings

[Down Under]

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

[bandersen]

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.

[Down Under]

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!

[bandersen]

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.

[bandersen]

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.


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

[Eric H]

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.

[Reece]

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

[bandersen]

Originally Posted by Eric H

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.

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.

Originally Posted by Reece

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

[Eric H]

Originally Posted by bandersen

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.

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 ) Anyway it's great for cleaning chassis, Chassi, Chassis's... (what is the plural of chassis BTW?)