Quote:
Originally Posted by jr_tech
Did the AM work normally just before the antenna loop was broken? Was the replacement the same as the original? What was the initial problem that you were trying to fix?
jr
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Yes, the AM did work well before the problem with the loop. The replacement is from a Zenith MJ-1035 and looks identical to the C-845's original loop. I don't see how that could have any bearing on whether or not the AM band works; the only thing I can think might happen with a non-original loop is the alignment might shift a bit, but the radio should work regardless.
If I remember correctly, I was having a problem with no reception on either band when I removed the original 12AT7. I would still be using that tube if a pin hadn't broken off flush with the glass at the base. The replacement is a NOS 12AT7 I purchased on eBay (BIN). The seller said, in the item description, that the tube was good (presumably he tested it first) and that he guaranteed the tube would be good when I received it. I have no way of knowing the cathode emission of either section, but the section that serves as the FM local oscillator must be working since, as I mentioned, the FM reception is great--I can hear stations 60+ miles distant just using the built-in antenna.
There might still be a problem with the band switch. I'll have to wait a while before I can tackle that problem, however, since the nearest Radio Shack to here is about ten miles distant (I live in a very small town with nothing in the way of electronics parts stores, or much else for that matter) and I do not drive. Once I do get a can of contact cleaner, though, I will try it on the band switch in my C-845; perhaps that will be all it needs to get the AM band singing again.
I don't know the condition of the electrolytic filter capacitor in the radio, although it must still be doing a half-decent job since I hear no hum in the audio, even on weak stations.