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Granger Associates was formed in 1956 by John Granger; the company specialized in antennas and aviation-related products. Their large log-periodic antennas (fixed and rotatable) can still be seen at airports and military installations. Granger Associates formed two subsidiaries, Granger Associates Ltd. , England, and Granger Associates Ltd., Australia. The UK subsidiary was responsible for the design of the model 272-6 transmitter, which was assembled by KW Electronics. Decca absorbed KW Electronics in 1974. The last of these transmitters were probably built in 1977, although Decca provided support afterwards. The transmitter has a distinctive Bauer styling, so I think that Bauer (which had been taken over by GA) had a say in part of the design. More information about John Granger is available at the Engineering and Technology History Wiki. Decca Ltd, London was taken over by Racal Electronics in 1979 to form Racal-Decca Marine, this must have been after June 1979 as I have a telex from John Church (G3HCH, now SK) dated June 1979 concerning GA model 272-6 maintenance and signed as DECCOM (Decca Communications, which was a subsidiary of Decca Ltd).
Claude Lyons CVR-1200 automatic voltage stabilizer.
Claude Lyons CVR-1200 automatic voltage stabilizer.
Claude Lyons Limited of Hoddesdon, Herts, UK, provided the CVR-1200 voltage regulator that stabilized the input voltage to the filament transformer of the Burle 8794 RF amplifier tube. However, Claude Lyons has closed down. They were established in 1918.
Specifications of the CVR-1200 "Automatic Voltage Stabilizer" :
- Input 204-252 volt
- Output adjustable 200-254 volt AC +- 0.3%
- Frequency 46-65 Hz
- Dimensions 11" x 7" x 6"
- Weight 20 kg
- Continuous current rating 5 A
- Power 1.2 kVA
Screenshot_2019-04-12 Contact Us - Claude Lyons.pngClaude Lyons CVR-1200_1.jpgFigure 1. End view of the Claude Lyons CVR-1200 automatic voltage stabilizer.
The automatic voltage stabilizer (T5 in the GA 272-6 circuit diagramme) is a very important component of the Granger 272-6 transmitter. It stabilizes the input voltage to the filament transformer; it has to be adjusted so that the output of the filament transformer is 5.7 volt exactly, under a load of 116 ampere. Lifetime of the Burle 8794 is closely linked to operating the filaments at the correct voltage. Figures 1 to 3 were taken of the CVR-1200 after removal, it will be packed for transport and moved to the location of the Station L replica. Some restoration is required on the CVR-1200 before re-installation into the transmitter. If one looks at closely at Figure 3 (you can zoom into the image a bit), there are some cracks in the pin board, there is also some damage of the wiring leading to R12, R13 and R14. This wiring needs to be replaced.
The other unit located in the 2nd transmitter (T102) has also been scrutinized and is in a better condition (Figure 4). This one can serve as example for restoration work.
Claude Lyons CVR-1200_2.jpgFigure 2. Isometric view of the CVR-1200.
Cluade Lyons CVR-1200_3.jpgFigure 3. Bottom view of the CVR-1200. A thin aluminium plate covers the bottom section, but has been removed for the purpose of this photo.
Claude Lyons CVR-1200 GA 272-6 TX102 T5.jpgFigure 4. The CVR-1200 control board of the 2nd GA 272-6 transmitter (T102). It is in a better condition than that of T101, but there is obvious discolouring of the wires attached to the three 11 watt resistors. The damage is clearly heat related, this leads to discolouring and brittleness of the wire insulation.
Claude Lyons TX102 T5_2.jpgFigure 5. The GA 272-6 transmitter (T102) CVR-1200 serial number is 546299, whereas that of T101 is 546296; a difference of only 3, which probably means that the two transmitters had their parts sourced at the same time.
GA 272-6-rf2.jpgFigure 6. Left rear view of the GA 272-6 HF SSB transmitter. Components are readily accessible.
With the rear double door of the GA 272-6 transmitter open (Figure 6), one can easily access the RF section. Shown here is the left portion of the transmitter cabinet, the six adjustable output circuits can clearly be seen. The transmitter uses two large rotary inductors for each band, a high voltage variable capacitor and a Jennings or English Electric Valve Co. vacuum capacitor. Each output circuit is basically a pi-L network. This configuration provides better harmonic attenuation than the standard pi-network often used in transmitters.
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