Collins Aerospace Museum

Dec-17 ···
233D Transmitter Restoration Project

I tore down the 100 KC RCA crystal tacked on a crystal holder that would fit (FT-241; bigger pins than the FT-243 with about the same spacing) the 3627.5 crystal that Rod brought in. That should get us on 7255 which should work to tune things up. (Of course, that is the EastCARS frequency so we shouldn’t use it on the air).

No deflection on any of the exciter meters and nothing heard on either the fundamental or harmonic frequency. Noticed that the keying relay didn’t appear to be actuating so checked the voltage across the coil and got nothing. Mike noticed that there were two screws missing from the chassis connector on the 175 tone chassis. He found replacement hardware, but still no joy on getting the key line over to the exciter. So there is an intermittent somewhere in the keying circuit.

I have a breakout box for the keying relay, so I’ll lift the ungrounded side of the relay coil and sub in a power source to see if I can get the oscillator and buffer to come up on frequency.

Mike is going to tack on some test points on the 175 tone chassis connector so we can set up the dial pulse levels and monitor the audio circuits that go to the speech amplifier, as well as the keying system. I did notice some channels selections that were not driving the Autotune to the right position, so we really need to get the dial pulses set up correctly with the scope.

Jules expected to have Don Grimm in today to verify the Autotune shaft/coupling fab work. Jules says that Grainger will have all the couplings and U-Joints in tomorrow.