Early Electronic Television
Ekco TA201 Restoration
This set is complete, with no rust on the chassis. The cabinet is in fair condition. Here is technical information on this set.
Cabinet. (pictures) Because the cabinet is in fairly good condition, we will attempt to have it touched up. The cabinet has been taken in to be repaired. Because of the number of damaged areas, the entire cabinet was refinished.
Chassis. (pictures) There are three main chassis and one small on in a small rack around the CRT. All are in good condition, with little rust. The rack assembly has some rust on it, but we should be able to remove it. The CRT is a Mazda CRM-71.
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.
There have been some modifications to the set which do not appear on the schematic diagram we have.
Today I finished restoration of the Audio/Video chassis, connected a signal, and got a reasonably good picture. I accidentally left the set on for a few minutes while I left the shop. When I came back, the set was on fire. The EHT transformer and the tar around it was in flames. Fortunately, little damage was done to the set. A few wires on the underside of the Power Supply chassis were melted, and there is tar everywhere on the chassis. I have sent the EHT transformer to be rewound. A new transformer will be built by the rewinding company, and should be ready on May 1.
I have a master switch in my workshop to turn off all 115 volt circuits, which I always remember to turn off when I leave. The Ekco was being operated from a 230 volt circuit, which is not controlled by my master switch. I plan to rewire the workshop today to change that. If I had been delayed another 15 minutes, the fire could have spread to the workbench and then to the rest of the building.
The new transformer arrived, and has been installed. I discovered that the width and height were inadequate. Two capacitors in the sweep section were missing in my set. After putting new ones in, the height was fine, but the image still isn't wide enough. I've tried new tubes (valves), and checked all components in the circuit. Changing the value of the cathode resistor in the horizontal (line) output tube cures the problem, but there must be another fault I haven't discovered yet.
Power Supply. (pictures) The power supply chassis contains two low voltage supplies and one high voltage for the CRT. The outer cases of most of the transformers and chokes are rusted. We will remove them and have them replated. The electrolytic capacitors are wet types, but we will not attempt to reform them. The cases are back from the replater. All of the electrolytic capacitors have been rebuilt, and the chassis has been re-assembled. All three sections of the power supply work properly. One of the high voltage (EHT) capacitors was bad, and has been rebuilt.
Time Base. (pictures) The Time Base chassis contains the horizontal (line) and vertical (frame) oscillators and output tubes (valves). The mounting brackets for the focus coil and yoke are badly rusted, so we will remove them and have them replated. The tube (valve) socket for one of the output tubes (valves) is bad, and will have to be replaced. The time base chassis has been restored. All the capacitors have been rebuilt, and the tube (valve) socket has been replaced. The Time Base chassis has been mounted back on the rack, with the Power Supply chassis and the CRT. The vertical (frame) and horizontal (line) sections works fine, and the CRT is good.
This chassis had several modern capacitors in place of the originals. In order to make the chassis look as authentic as possible, I removed the paper label from one of the original capacitors and scanned it into my computer. I then used Photoshop to create new labels for the capacitors which had been replaced with modern ones. I created a label for a 25 mfd/25 v, a .22mfd/525 v, and a .5 mfd/450 volt capacitor in this way. The labels were then glued to shells removed from paper capacitors taken out of old immediate postwar sets.
Audio/Video. (pictures) The audio/video chassis contains 3 RF amplifier stages, a video detector, a video amplifier, a sync separator, and 2 audio RF amplifier stages. There is another small chassis, with one tube (valve), a RF preamplifier for weak signal areas.
This chassis also has several modern capacitors. I have made imitation old ones as described above.
The chassis also has several modifications which are not on the schematic. Some appear to be factory changes, while others were done later, probably after the war. In each case, a decision has to be made whether to keep the modifications or restore the set to the design on the schematic.
One modification involves an added tube (valve) to drive an external speaker, eliminating the need for a separate radio to receive the audio. Because all the parts used in the circuit are postwar, I have decided to eliminate it.
Another involves the addition of a potentiometer in the sync separator circuit. This was probably a factory modification to improve the operation of the set. I will keep that change.
Another involves the addition of a noise limiter in the audio section. Because the audio in the 405 line standard was AM, it was subject to ignition interference from passing cars. Nothing could be done about interference with the picture (which was also AM), but a noise limited kept the volume of the interference less objectionable.
The final modification was the addition of the RF preamplifier chassis. This also appears to be a postwar modification, so I will not use it.