Early Electronic Television
RGD 382-RG Restoration
This page will follow the restoration of the RGD pre-1945 TV set now in progress. Newly added information will be in red text.
The set was shipped from England, and arrived with most of the chassis removed and packed separately. Also packed separately were the CRT and the record changer.
Fortunately, we have a schematic diagram of a postwar set which uses identical RF and deflection chassis. Here is technical information on this set.
The restoration of the set is now complete. The set is now displaying pictures from a VCR.
The restoration will be in four parts:
Cabinet. (pictures) The cabinet is in fair condition, with damage to the veneer and many scratches. There are some extra holes inside the top where the wrong radio was installed, and the wood panel for the radio is missing. First, we will photograph the cabinet from several angles to make sure we re-assemble the set properly. Then, we will remove all non-wood pieces. The cabinet will then be taken to Old World Furniture Restoration to be refinished. The cabinet is now being evaluated by Old World. The veneer on the top is in very poor condition. It is expected that the restoration will take about three months.
We have a poor definition photo of the missing radio panel and will attempt to get the owner of the only other existing RGD to send us better pictures. A lid from another RGD set of the same era was included in the shipment, and can be used to make the radio panel.
The veneer has been re-attached, and the cabinet is now being stained.
The restoration of the cabinet is almost done, with the final coats of lacquer being applied.
There are several wiring harnesses, connecting the three chassis, the CRT assembly, and various controls. Some of these are made with rubber covered wire which has deteriorated. The harnesses are made up of several wires inside cloth outer coverings. By cutting off the deteriorated wires right at the end of the cloth coverings, it is possible to solder new wires with similar appearance, and to heat shrink them to the old wires.
The rebuilding of the wiring harnesses is completed. One of the power (mains) switches was defective. We were able to dissasemble it, clean out the corrosion, and reassemble it.
The cabinet is now back from the restoration company, with the exception of the radio panel, which must still be made. The top panels have been re-assembled, and the CRT and power supply and time base chassis have been re-installed. The internal cabinet wiring has been put back in. The set now displays a nice raster, with a sharp, bright image.
This week we expect to get the power transformer back from the rewinder. After it is installed in the audio video chassis, we can begin to try to get that part of the set working.
The wooden radio panel needs a hole cut in it for the radio dial and frame, and a wooden frame simulating the missing bakelite frame will be made. Then the radio can be mounted.
Finally, when the power supply chassis and speaker for the radio arrive from England, the set can be completed.
The spring assembly and top were installed today.
I have been having trouble finding the proper color felt to install on the top of the cabinet, so I am attempting to dye some light brown felt the proper color.
The dying didn't work very well. The color was inconsistent. I have located some billiard table cloth that is very close in color, and have ordered enough to do the set.
The TV Chassis. There are three chassis: Power Supply, Time Base, and Audio/Video. Each 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 also had to be rebuilt.
Power Supply: (pictures) This chassis is in good condition with little rust. It contains the LV and HV supplies.
The power supply chassis has several electrolytics from the postwar period. We will attempt to get pre-1945 cans and install new electrolytics in them. The one pre-1945 can on the chassis has been rebuilt, and the replacement pre-1945 cans we found have been rebuilt.
The high voltage (EHT) transformer is also a postwar replacement. We will look for a pre-1945 one, but finding one will be almost impossible.
After testing the electrolytics, 220 vac was applied to the chassis. All three sections (2 putting out about 350 volts and one about 6,000 volts for the CRT) appear to work.
After hours of trying to get the CRT assembly to produce the proper voltages, I discovered that the pin connections on the plug that connects the CRT assembly to the power supply were wrong. Apparently, either the power supply or the CRT assembly is not the correct one for that set. Changing the pins made it work.
Applying power to the CRT produced a bright, but out of focus, image, indicating that the CRT is good.
Unfortunately, one of the three power transformers started smoking. The transformer is now being rewound.
With the exception of the power transformer, the restoration of the Power Supply chassis is complete.
The rewound transformer arrived today and was installed. The power supply now works properly.
Audio/Video: (pictures) This chassis has a considerable amount of rust. It contains the RF oscillator and mixer, the video IF stages, detector, and video amplifier, the audio IF stages, detector, and amplifier. We will remove as many components on the top of the chassis as possible to allow cleaning of the rust. Solvents and steel wool will be tried. The rust is so severe that it was decided to strip the chassis and have it replated. Fortunately, there are no rivets used in the chassis, and most of the wiring can be removed in one piece.
When the chassis came back from the replating company, the outside was chrome plated on top of the nickel. The chrome has been removed, and the components have been remounted to the chassis. The paper and can electrolytic capacitors have been rebuilt. Finally, the cable that goes to the power supply chassis has been repaired with small pieces of heat shrink tubing.
The Audio/Video chassis restoration is now complete. The next step is to apply a RF signal and test it.
With the power supply completed, is was possible to start testing the audio/video chassis. First, the local oscillator was tested, and found to be generating a signal at about 35 mHz. Then, a 45 mHz video signal was inserted in the input. The 10 mHz IF signal was followed through the three amplifier stages. Finally, we checked for video at the output of the detector and at the output of the video amplifier. All the video circuits appear to work. However, in the process we discovered three bad SP41 tubes (valves). We have no spares. So, further work will have to wait for some new ones. We are also still waiting for a 405 line modulator.
Today we connected a NTSC video signal to the grid of the video amplifier tube (valve). We were able to get a good picture; the vertical (frame) and horizontal (line) frequency controls could be adjusted to the American rates. However, the picture was about one inch too narrow, because the horizontal section was designed to operate at a much lower frequency than the 15,750 Hz of the NTSC system.
Time Base: (pictures) This chassis is also in good condition with no rust. It contains the sync separator, vertical (frame) oscillator and output, and horizontal (line) oscillator and output. Since there are only a few paper capacitors on this chassis, I decided to try it out without changing anything. I installed the oscillator tubes, connected the power, and I had both vertical (line) and horizontal (frame) signals. I then installed the output tubes. Again I had signals at the yoke connector.
Finally, I connected the CRT and yoke. On powering up, I have a nice raster, perfectly in focus. The width is inadequate, but changing the paper capacitors will probably solve that. The CRT looks like new.
All the electrolytic and paper capacitors have now been rebuilt. Restoration of this chassis is now complete.
The Radio Chassis: (pictures) The radio chassis is in fairly good shape, with a small amount of rust. It contains the normal circuits for radio operation. A strange feature of this set is that it has two speakers and related audio amplifiers, one for the radio and one for the TV.
There is a second chassis, containing the power amplifier and power supply, which is missing. We will attempt to find an original, and if not, we will try to build one as close as possible to the original. The radio speaker is also missing.
A radio containing the proper amplifier chassis, plus a speaker, is on the way to us.
We began the restoration of the radio chassis today. Using steel wool, most of the rust was removed. Then the chassis was cleaned with mineral spirits. The cable to the eye tube (valve) has been restored using heat shrink tubing, The one large and one small can electrolytics have been removed for restoration.
The elastic belt connecting the tuning knob to the tuning capacitor has completely deteriorated. We have to find a suitable replacement. For now, a rubber band is being used.
The restoration of the radio chassis is now complete. When the power amplifier/power supply chassis arrives we can test it.
This week I have been working on the radio chassis. First, audio frequencies were inserted at each amplifier, working backwards to the detector. A mistake was found where a capacitor was soldered to the wrong place when it was restored. When this was corrected, all the audio stages worked properly.
Next, a 455 kHz IF signal was inserted at the mixer. After finding a screen resistor which had not been soldered to B+, the IF stages worked properly.
Finally, The operation of the local oscillator was checked using a spectrum analyzer. It was working properly.
Then, I tried tuning an AM radio station. It worked. The tuning eye also works correctly.
The next project was getting the motorized tuning working. The motor would not turn freely, caused by a pin in the coupling assembly rubbing against the chassis. Then, the motor would operate only in one direction. A wire was pinched under a bolt, shorting it to the chassis. After repairing it, the motorized tuning worked properly.
The rubber band tuning belt was replaced by several turns of heavy dial cord.
The radio is now working properly. When the wood panel is finished, it can be installed in the cabinet. The new panel is completed and installed.
The Radio Amplifier Chassis: (pictures). We received this chassis from England today. It is in fair condition, with a moderate amount of rust. We will remove as much as we can with steel wool.
There are some differences between this chassis and the schematic we have of the one that came with the TV set. Different plugs are used to connect the radio and the radio amplifier chassis. We will try to find out the proper arrangement, and modify the chassis accordingly.
We have completed restoration of the amplifier chassis, using our best guess on the proper plug arrangement. After applying power, the output transformer started smoking. Fortunately, this is an easy part to find.
The Record Changer: (pictures) The record changer is a Garrard R.C. 1/A - 2/A. It is in fairly good shape, with some rust. The motor and gears appear to turn freely. One plastic cover is broken, and the felt on the turntable is in poor condition. We will clean the changer and attempt to remove the rust. We are also looking for a specialist to restore this unit.
After investigation, we have decided to do the restoration. We have disassembled the changer, and have taken the base, which has a gunmetal finish, and the chrome parts to a local metal refinisher.
The base and chrome parts have been refinished. Unfortunately, the color of the base is not correct, so it will have to be repainted.
Today I took the base and turntable to a gun bluing shop. They told me they can reproduce the original finish on the steel pieces, but the aluminum tone arm and record holder will have to be anodized. I am looking in to a shop in Dayton that has that capability.
The bluing didn't work, apparently because the metal has some sort of plating on it. I will try the Dayton shop next.
Finally, a decent finish on the changer. The shop in Dayton put an oxide finish on it, which looks very similar to the original. I have cleaned the motor and changer assembly, and glued together some plastic parts which were broken. The next step is to reassemble the turntable and test its operation. The cartridge has been rebuilt.
There is a problem with the motor. It overheats, and I have tried everything I know to fix it. So, I will find someone who can repair it.
The changer has been re-assembled.