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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders. |
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16th Jul 2019, 2:02 pm | #1 |
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Join Date: Feb 2019
Location: Congleton, Cheshire, UK.
Posts: 609
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Windsor (Taylor) 65c missing frequency ranges...
I've finally got my stripped & twiddled 65c sig-gen functioning to some degree, with a lot of help from a home-drawn diagram from elektrotanya. Previously it was totally dead except for filaments and indicator lamp & now with some re-wiring and repair to a damaged coil I have a test tone (more on this shortly) and can modulate this over the 100-300 and 300-900Kc/s ranges with some accuracy (I can inject to the IF of a couple of test sets with the needle between 455/465 marks).
Unfortunately any range higher than the 300-900 is still not modulating anything, in fact I believe the modulation falls on it's face at the top of the 900 range. When modulation is dead I can also hear the AF tone change, speaking of which I'd estimate the tone when modulating is actually closer to 300c/s than 400, when modulation fails this seems to jump to the correct 400c/s tone albeit much more quietly. Without having a valve tester, I'm wondering if it could be a faulty valve although I have switched the 6J5's around with no change. I would have expected a dud valve to fail at the lower end also so not very sold on that idea. All caps have been changed with the exception of 3 flat mica jobs and one ceramic dog-bone which all tested good. Resistors have been checked/replaced as required and I'm 99.9% sure there's no other open coils (surely this would only affect 1 range anyway?) so I'm a little stumped and would greatly appreciate either suggestions of what I could have missed, or if someone has a record of voltages checked from their working example/specified correct voltages that would be very helpful too. Thanks, Dan |
16th Jul 2019, 4:20 pm | #2 |
Banned
Join Date: Feb 2019
Location: Congleton, Cheshire, UK.
Posts: 609
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Re: Windsor (Taylor) 65c missing frequency ranges...
Correction to my last, I've had a scope on the output now and it continues to work up to 900Kc/s it's actually on the lowest range where it dies again, cut off is around 125Kc/s and needs bringing up to about 165Kc/s before it starts up again.
I am beginning to wonder about valve quality now but would certainly be thankful for suggestions as before. |