Museum Hours:

Saturday 10-6

Sunday 12-5

 

Early Electronic Television

Andrea Kit in Custom Cabinet Restoration

The Cabinet: The cabinet is in mint condition.

The Chassis: The chassis has been painted with a grey metallic paint, which probably hides rust. We will rebuild the paper capacitors and put modern electrolytics in the original cans. Here is technical information on this set.

The 300 volt power supply transformer is bad. After applying power, it overheated. Ed Dinning built me a new one that is almost exactly the same size. Here are the steps I used to replace the transformer. Below is a picture of the original and Ed's replacement:

Ed's modern wires are cut, and old style wires soldered to them. Heat shrink tubing is used to cover the bare wires.

Next, the edges of the new transformer are spray painted flat black to match the original. The new core is about 1/8 inch narrower than the original, so spacers are used inside the two outside shells the make the new assembly the same width.

After replacing the transformer and rebuilding all the paper capacitors, I got a nice raster. The local oscillator would not tune up high enough to receive channel 3, which is the channel I use at the museum, so I had to remove one turn from the oscillator coil. The original two channel tuner must have been made for channels 1 and 2.

Because the chassis had been subjected to water, two of the controls (contrast and tone) were frozen, and could not be fixed. After replacement, I applied RF, set the local oscillator frequency, and started debugging the RF and IF sections. Every adjustment had been messed with. Fortunately, this set has no trimmers for the video IF, and it was only necessary to peak the audio IF trimmers to 8.25 mHz and set the upper adjacent picture carrier trap to 14 mHz.

While checking the alignment the high voltage (EHT) transformer started smoking, so a new one will have to be made, or the old one rewound. A new one was wound by Ed Dinning, but it failed a couple of hours after installation. He will make a replacement.

This set uses a bias battery in the audio amplifier stage. After 60 years it is obviously bad, so I rebuilt the original using a hearing aid battery.

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The original cell

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The new battery, with a lead soldered to it, next to the empty shell

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The new battery installed in the shell

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Hot glue is installed around the new cell

After installing a new transformer, the set works perfectly