The plan was to do a test run of the coils. Unfortunately the CIG gods had other plans for us. The coils were to be driven by a TCS WW2 era military transmitter.
Eric had previously acquired two of these transmitters, and both were supposedly operational. Neither transmitter turned out to be functioning when we attempted to fire them up. The transmitters receive their HV supply from a motor/generator unit called a dynamotor, which in turn is run off a 12 volt battery. Unfortunately the dynamotor was mis-wired, so it wasn’t providing filament voltage or plate voltage to the transmitter. After going through the dynamotor wiring checked against the schematics we were able to correct the mistakes. (Tracking down wiring problems in big bundles of wire can be very tedious)
A second attempt was made to fire up the transmitter and this time smoke started coming out of the power supply cable where it connected to the transmitter. It is a multi-pin connector, and some of the wires were connected to the wrong pins. So all new cables were made with new wire, a very time consuming task. There were around 15 pins on each end of the cable, and 2 cables to be made. So around 60 solder connections to be done, and they were difficult to solder! After that to avoid further problems we went through the transmitters to check for problems. More issues were encountered.
A ham had previously been inside the transmitter and attempted some ill advised modifications. After much checking against the schematics again we were able to isolate the modifications and reverse them to correct specs. Also we discovered some broken parts. One of the adjustable loading coils (tuning inductance) was broken; its ceramic core had shattered at some point.
After I had spent 5 days there, I had to return home to go to work. I spoke with Eric on the phone the following day and he was able to get the transmitter going, and tune the coils to resonance. The resonant frequency of the coils turned out to be 2.4 Mc, slightly above the designed value of 1.8 Mc. I’m not sure what caused the discrepancy yet, but I will investigate on the next visit.
It was a good exercise in troubleshooting though. Eric is absolutely brilliant in this area. He seems to have an uncanny intuition on where exactly to look when something is wrong. That kind of skill can only be gained through decades of experience, I was glad to have him there!
I should be going back in about a month to make another attempt at test firing the coils.
Here are some pictures of the coils mostly completed: (still need a gradient ring on the secondaries)
The coil stands for the primaries and secondaries were designed so they would exactly slip inside each other. You can see that in the pictures.












































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