Museum Hours:

Saturday 10-6

Sunday 12-5

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Early Electronic Television

Westinghouse WRT-701 Restoration

The Cabinet.  (pictures) The cabinet is in excellent condition, but is missing its CRT mask and radio escutcheon. We will have a mask made and are attempting to find the correct escutcheon.

The Chassis.  There are three chassis in the set: TV, Radio, and Radio Power Supply.

TV Chassis. (pictures) The TV chassis is identical to the RCA TT-5 chassis. This chassis is in fair condition, and is mostly complete. Here is technical information. This set had been previously restored, and has modern capacitors.

The mounting brackets for the chassis are missing. We will make replicas.

Several modifications were made to the chassis. First, an extra electrolytic capacitor was added in the +300 volt line, isolating the sweep circuits from the local oscillator. Second, FM sound was added. the 6B8 amplifier/detector was replaced with a 6AB7 (the tube socket was changed, too, from bakelite to ceramic), and a 6AL5 detector was added. The Final IF transformer was changed to one designed for FM. This transformer looks to be a RCA part, and is the same style as the original AM transformer.

The extra electrolytic is shown between the second row of IF cans. The 6AL5 can be seen between the first row of IF cans. Behind it is a small electrolytic used in the FM detector circuit.

Finally, the RF input line, originally a two conductor cable in a cloth sheath, was replaced with 300 ohm twinlead.

I suspect that the electrolytic and FM sound were added right after the war, and that the twinlead was added when the restoration was done (probably after 1970). We will leave the extra electrolytic there. The twinlead will be replaced with something that looks as much like the original as possible.

The chassis will be cleaned with water and a mild detergent using soft brushes to get into small places. Then, all paper capacitors will be replaced with modern ones (see the procedure for this). Each electrolytic capacitor will be tested for leakage and capacity. If bad, new electrolytics will be installed inside the old ones. The high voltage (EHT) capacitor had been replaced with tubular ones, placed under the chassis. An old can we have will be rebuilt and installed.

After cleaning the chassis, we removed the high voltage (EHT) capacitors from under the chassis and installed new capacitors in an old shell we had. Though it isn't identical to the original, it is from that era, and looks very similar.

 

Next, we replaced the missing feet. There are 6 of them, 4 large and 2 smaller. The smaller ones came from a 1939 RCA radio, and we made the larger ones:

Chuck Azzalina generously gave us enough old RCA capacitor shells to replace all the modern ones that were in the set. Here is the underside of the chassis after all the capacitors have been replaced. We also replaced a number of modern resistors:

We decided to return the set to the original AM sound. This involved removing the 6AL5 and related parts, rewiring the octal socket for the original 6B8. When the set was converted to FM, all AGC components were removed. We replaced the original parts to restore the AGC.

This set worked when we got it, so nothing more needed to be done after the above restoration was completed, other than tuning the local oscillator to channel 3 and peaking the audio IF transformers.