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All recapped and off resistors changed (hopefully correct). Came up nice with just a little static. Started checking things by moving a short antenna around a got my SSTrans fairly loud with a short antenna on the grid cap of the 78 first IF! Nothing with the antenna anywhere in front of this. Strange.
Started injecting an RF signal at the antenna input, nada. Hooked about 6 feet of wire back on the above 78 grid cap and voila signal generator tracked the dial across the BC band nicely from the antenna input.
It would seem that due to the above that the RF amp and first detector are working properly. Any ideas? Needing a short "antenna" on the grid of the 1st IF has me thrown for a loop.
http://www.nostalgiaair.org/PagesByModel...013125.pdf
Jerry
A friend in need is a pest! Bill Slee ca 1970.
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Check your coils. RF and Det-soc.
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Have you aligned the IF stages?? Sounds like you've got some funny business going on in there. It may be oscillating or something. Give it a try and see what happens.
GL
Terry
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Sounds like a possibility is an open IF input coil secondary, or its connections to the tube. Also check to make sure there is good contact between the grid cap and the wire where it goes into the tube, also the wire coming out of the IF can to the grid cap. It may not be your "antenna" at all, but a poor connection that you are affecting when you connect the "antenna". If it IS the "antenna", it would tend to indicate the open transformer theory, since you would then be picking up radiation from the 1st Det/Osc tube.
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Thank you all for some great ideas to go a checking. The idea of the "antenna" acting to pick up the something from up front makes sense. Time to check some coils. I have not aligned the IF yet but did hook the generator to the grid cap of the IF tube and swept the gen and seems like the 2nd IF transformer peaks around 270 (should be 260). At this point I don't believe I can get a signal through from the 1st detector the way it is working.
Jerry
A friend in need is a pest! Bill Slee ca 1970.
(This post was last modified: 05-03-2013, 09:19 PM by
jerryhawthorne.)
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All questions deserve closure, sorry, this one is not too satisfying. Except for me. Started with an RF signal at the antenna and worked my way towards the rear. I had to loosen up some parts to move out of the way, getting to plates on tube sockets. Looked great on my scope all the way to the plate of the of the IF amp. Why didn't it work? Put back the antenna and darn if it didn't play nice. Tightened everything back down and still working well. Don't ask me why. Did an alignment and perked up even more. On to chassis cleaning and perhaps I can kill it again.
Jerry
A friend in need is a pest! Bill Slee ca 1970.
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Just to ensure it won't go away as suddenly as it came, wiggle the tubes, take a plastic rod, knock on parts, wiggle wires. Basically look for some cold soldering spots / bad connections.
Personally I hate when something starts working for no good reason.
