1957 RCA Victor TV Model 21-PD-8115


Introduction

    This is my most recent acquisition, off of Ebay, and as of this writing, the set has not even been mine for an hour. Most of the information you will see here (until this page is updated) was obtained from Sam's Photofact set 386, folder 4. Thanks to the wonderful pictures prepared by the seller, I was able to find out minute detail about the set. For all practical intents and purposes, it is the 21" version of my 14" portable.

The Chassis

    This TV set uses a KCS107 series chassis. In this particular model it is chassis KCS107A. Other chassis designations are KCS107B, C, and D. These are 16 tube chassis. This model was also available with an optional UHF tuner. Models equipped with this option had a U at the end of the model number. Sets equipped for UHF have one additional tube.

      

Tube Line-up 

Tube Type Function
4BQ7A RF Amplifier
5CQ8 Mixer-Oscillator 
3CF6 1st Video IF Amplifier
3CB6 2nd Video IF Amplifier
3CB6 3rd Video IF Amplifier
6AW8A Video Output-Sync Separator
3AU6 Sound IF Amplifier
3DT6 Audio Detector
5AQ5 Audio Output
6CG7 Sync Amplifier-Vertical Multivibrator
5CZ5 Vertical Multivibrator-Vertical Output
6CG7 Horizontal AFC-Horizontal Oscillator
12DQ6A Horizontal Output
19AU4 Damper Diode
1X2B High-Voltage Rectifier
21DFP4 21" Silverama Picture Tube

Two selenium rectifiers act as low-voltage rectifiers, and one 1N60R crystal diode acts as Video Detector

Restoration

Preliminary Diagnosis

    Restoration will begin as soon as the set is shipped to me. Preliminary diagnosis from the information provided by the seller seems to indicate a bad 1N60R crystal and possibly a few bad tubes in the tuner or video sections. Even though it was stated that the set does work, it was also stated that no stations could be received. Most people not familiar with televisions will say a set works if a raster is present on the screen. This is in fact true because the high voltage and sweep circuits are working. No picture or sound will appear. Therefore, trouble would seem to stem from the video sections or tuner. The first part I will probably check will be the 1N60R video detector.  The rest of the restoration will mainly consist of cleaning contacts and pots, replacing wax and paper caps and probably the removal of the selenium rectifiers from the circuit. They will be replaced by modern silicon ones hidden from view. This is actually a good habit to get into doing. If one of the selenium rectifiers should fail, it could possibly catch fire, or emit poisonous gases. The set does look very clean.

    When I update my page after digging in to the set I will leave the above paragraph and see how far off my predictions were.

The Set Has Landed!!!!

    It has arrived and it is working, err, somewhat. Let's start first with what it is doing: It has a raster. It even has snow, and when you hold the antenna right, you can make out a picture. When I found the speaker leads all unhooked and neatly coiled and tapped to the side of the cabinet I hooked those up, and, to my surprise, when the tuning control and antenna were positioned just right, loud, clear, undistorted sound poured out of the speaker. So, it sounds like it works, right? Wrong!!! Let's see what its not doing, or doing wrong.

    The biggest problem so far is poor vertical linearity and vertical foldover in the lower part of the screen. The horizontal sweep section seems to be working perfectly, as I had a full-width action all the way from the get go without twiddling the controls. But, the horizontal hold seems to do funny things at the extreme ends of its rotation, but it is pulling into sync. Vertical hold is working correctly. Tuning is also scratchy at times, but this will probably fix itself as I replace parts because most of the problems I noted with tuning happened when I adjusted other controls. So it is probably just dirty controls and leaky decoupling components in the B+ supply. The filters and rectifiers actually seem to be working properly.

The Set Come to Life

Well all of those pesky capacitors have been replaced, excepting those on the power supply. They will be next soon. after some adjustments, the set has been watchable. A true test of its capabilities was found when I hooked it up to cable. A slight amout of vertical stretching is occuring at th very top-most part of the screen, and there is some horizontal wiggle in that area too. Otherwise, no problems.

Now that the set has had a little use,it has developed a new problem. After being on for a while, the horizontal hold will start to destabalize, and eventually loose sync completely. When I trake the set apart next to rebuild the power supply, I will address this new problem. Tube substitutions have proven it is not a tube.

Photos will be posted soon

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