I started working on this set I picked up at a thrift store about 2 years ago today. It's kind of a cheap set, series-string, and all but the horiz output, vertical, and power supply, are mounted on that big board on top of the chassis. But it's no Muntz, it has a good 3 stages of IF. The crt tested very weak but I gave it a few short 2 second bursts with the rejuvinator, and it seems to have come back, now it registers about 420/100 on the crt tester. I'm eventually planning on repainting the metal cabinet, but this weekend I just want to see if I can get it going. Here's a pic of how it sits now.

Cool! Is that a mix of PCB and point to point wiring?

At least it appears that most components are accessible.

Are you replacing the selenium rectifiers with silicon diodes?

If for some reason you want to keep using the selenium rectifiers and one needs replacing I just bought a grab bag of NOS ones that appear to be identical to what's in your set.

John Y.

Only the horiz output (but strangely not the horizontal oscillator), HV, vertical, and power supply, are mounted on that lower chassis, everything else: sound, IF, video amp, ... are all on that big board on the upper part of the chassis. I replaced the selenium rectifiers with diodes, but I just left them sitting in there (not at all connected to anything) because I thought they looked cool. This set has seen a lot of use, it's full of many previous repairs, and it has very few of it's original tubes.

What's good for cleaning circuit boards? This board is full of this sticky gook even the laquer thinner isn't that good at cleaning.

At our lab I use Miller-Stephenson MS-725 or MS-755. The 755 has the advantage of working on greases, organic flux, and ionic salts. Because of the concern of ozone depleting chemicals, the best performing products are no longer available.

I design and build detectors for Nuclear Physics type experiments. They are extremely sensitive to certain contaminants so cleaning is very important to us.

If there are no ionic salts to deal with, I find brake cleaner works quite well since it's mostly trichloroethylene. However, just as with lacquer thinner you need to be careful what you get it on. Also, it's a cumulative liver toxin and suspected carcinogen. Use it in a well ventilated area with splash goggles and gloves.

The MS-xxx products are a bit safer but one should still exercise caution.

Oh, and there are the vintage radio people that put the whole chassis in a dishwasher. I haven't gotten up the nerve to try this yet. Perhaps if I ever find a set that's been in a flood I will.

John Y.

I'm a firm disbeliever in the dishwasher treatment. There are some components in old radios and TVs -- coils, potentiometers, etc. -- which were never intended to be submerged in water or run through a dishwasher. I have never met a chassis that I couldn't clean with less harsh methods.

Some people claim to use it with success, but they all seem to live in hot, sunny climates where you can leave the chassis to bake in the sun for three days, or else bake it in an oven.

Just my $0.02.

Phil Nelson

I'm a firm disbeliever in the dishwasher treatment. There are some components in old radios and TVs -- coils, potentiometers, etc. -- which were never intended to be submerged in water or run through a dishwasher. I have never met a chassis that I couldn't clean with less harsh methods.

Some people claim to use it with success, but they all seem to live in hot, sunny climates where you can leave the chassis to bake in the sun for three days, or else bake it in an oven.

Just my $0.02.

Phil Nelson

I agree with you. I read one account where the individual had a devil of a time figuring out why his radio no longer worked after putting it in the dishwasher when it did before. He checked all the components and they were o.k. He finally discovered the problem was with the IF transformers. They were wound on wooden dowels which had now become conducting.

I don't remember his fix for that. But, he was still happy with the dishwasher treatment. That would have ended it for me. But, I'm not as fussy about appearance.

John Y.

Thanks for the ideas, I just cleaned it again with laquer thinner because I wanted to work on it in the middle of the night when all the stores are closed. It eventually worked. I was worried the laquer thinner would start dissolving the board, but it didn't. I made some progress today, finished my recap, also tested all the tubes, only 2 were bad: sound IF 5BR8 and output 5AQ5. I was lucky and already had replacements for both. I currently have good sound but only a blank raster, also I need to replace the vertical hold control (it uses a plastic shaft which is broken off inside the control itself).

Probably something in the video detector circuit. I'd look there first. Could be as simple as a dirty tube socket in the video amp section too.

The problem was a loose resistor connected from the power supply to the contrast control, someone had replaced it at one time and just cut off the old one and twisted it on to the old leads without even using any solder on one side and it came undone on that side, I soldered it directly to the board. It works now for the most part, except I can't get enough vertical height.

The vertical problem was the height control itself, I tried cleaning it but it did no good, I'm going to have to replace it. I just put in a resistor across it for now and have full vertical height.

...

It only worked for about 10 minutes before I started to slowly loose vertical height again, something else must be going on. I just looked at the clock on my computer, I stayed up all night working on this set without even realizing it, I thought it was just a little past midnight and it's already past 5.

...I stayed up all night working on this set without even realizing it, I thought it was just a little past midnight and it's already past 5. Hoo-boy that sounds familiar.... :o

Sounds like you need a can of 'freeze spray'. If it starts out ok and drifts with time, then it's a thermal problem. Freeze spray lets you instantly, selectively cool a suspect component. Be sure to read the can if it's conductive :)

Armed with that stuff, thermally related drift gets found and fixed in minutes.

Caught short on "freeze mist" or "freeze spray", you can take a can of "blow off" as used for applying compressed air to delicate assemblies, and invert the aerosol can before applying, and you have the same thing as the former.

Just a hint.... :thmbsp:

That TV is one of the most troublesome of its time. Sylvania made that set for RCA as well so you may see the identical TV with an RCA label.

The top PC board is a source of bad solder joints, poor quality components and bad ground connections. The heat from the sweep circuits cooks the PC board and its parts. The board material is very fragile and the conductor will easily separate. Make sure the PC anchor screws are tight on the supporting rails as they provide a ground path.

Carefully flex the board and look for changes. Allow plenty of time.

A good cleaner is CRC Electronic Cleaner, safer than brake cleaner for electronics, available at all auto parts stores.

Reece

According to the MSDS for CRC Electronic cleaner the main solvent is isohexanes. Hexanes are certainly safer in terms of being less agressive.

They are extremely flammable however so one shouldn't smoke or turn anything on until it's dry and the fumes are gone.

Also, by following Reece's suggestion you'll be using a product with known ingredients. Brake cleaners have different formulations and you have to read the label first to know what you're getting.

John

What crt does this set use, I might be able to find one cheap< doug

That TV could use either one of two tubes; 17BWP4 if it has no ion trap and a 17BVP4 if it uses one. They are otherwise interchangeable. I have both tubes NOS rebullit aluminized very reasonable. Send me a PM if you're interested.

Don