My Attempt at Predicta Restoration

[Reece]

I'm entertained already just following your progress, good show. I've used that electrolytic rust-eater setup before but with "washing soda" (sodium carbonate) available at supermarkets. It really eats the rust off of some nasty cases.

[PredictaNoob]

Originally Posted by Reece

I'm entertained already just following your progress, good show. I've used that electrolytic rust-eater setup before but with "washing soda" (sodium carbonate) available at supermarkets. It really eats the rust off of some nasty cases.

Thanks! Yeah, I tried the washing soda once too, but I really couldn't tell any difference from when I used salt. The salt is "kosher", so maybe that's what makes the difference

I did find that with either agent, you end up with a big ole bowl of yuck. I've been dumping it in my German neighbors flower bed since she continues to let her yappy little dog crap on my front stoop. I watched her looking at her 'rusty' marigolds in dismay yesterday afternoon. What a hoot.

[DaveWM]

are you planing to pull the main board to get at the bottom side? there are pros and cons

Pros:

allows careful inspection of solder joints and neat replacement of any bad parts, including tube sockets.

Cons:

there are a LOT of wires that are connected to it, and you have to unbend and desolder some big ground stakes.

My approach
On mine I Opted to take the do no harm approach. That is leave it as original as possible, remove as little as possible until I had a chance to evaluate the existing status. I did replace all paper caps and check the can caps. On mine the thin can cap next the the transformer was open. It was a low voltage can 2 section IIRC.

After that I pulled the HOT and did a slow power up with a variac looking for smoke and any signs of distress. checking for voltage drop at the B+ and checking the current.

Next I put in the HOT with an adpater to check the current, power up this time fast and I got raster and checked the current, all good.

then the signal to the tuner and another powr up this this time and its looking pretty good but for the brightness control, an open resistor was the culprit. that is about all it took.

I did have some tube socket issues, the vert out was intermittient, (line on screen, wiggle socket and it comes back) that needed to be replaced.

Also the HV would go away, turned out to be an intermittent damper tube, this time not the socket but a ground stake that completes the filament circuit.

I was able to get replace most of the paper caps with out removing the main board, I used solder braid and low watt iron. On some of the caps that had pads shielded by the chassis I used my solder gun and bent the tip 90 degrees to get at the pad. lots of care and braid to clean it up. Extemly easy to lift a pad this way so you need to go slow and never force a part down.


I was lucky I did not need to replace any other sockets as many are hard to get at and would most likely require pulling the board, but as I said do no harm.