Troubles With FM Alignment On 46-480 - Printable Version
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Troubles With FM Alignment On 46-480 - Owells - 08-06-2008
AM aligned beautifully. FM has no reception at all to begin with. Steps 1 and 2 of FM alignment go well but in step 3 C32 is very unstable, or maybe eratic is a better word, and just by touching it with my alignment tool increases reception slightly. When I am able to get a somewhat stable reading and proceed to step 4, I'm seeing no changes at all throughout this step of the procedure. I guess pull the trimmer can out and check trimmer C32 to start with? Other ideas would be greatly appreciated.
- Texasrocker - 08-08-2008
sometimes, I have found the pushbutton contacts were not making good connections in some cases. Also, sets that use the loctal-type tubes & sockets were notorius for not making good connections unless the pin connections are all cleaned really,really well. I usually scrape the loctal tube pins carefully with a exacto knife to make sure they get good connections all around the tube sockets (bright shiny clean). Just tryin to help with a couple suggestions of sometimes overlooked culprit-probs in sets that use the local-type tubes.
Problem Solved? - Owells - 08-09-2008
Thanks Tex. When I put this thing together I cleaned all the Loctal sockets along with the tube pins themselves. Well today I pulled the tubes and cleaned the sockets again with a small wire brush. Similar to a gun barrel cleaning brush but smaller. I also took a piece of emery cloth to the tube pins. Still didn't work but when I wiggled the tubes it would work again. So I took the tubes and actually bent the pins out just a hair and reinstalled them. Seems to have good FM now. Who ever invented the Loctal and what good is it if they weren't dependable. I've had trouble with them on another radio. Anyway I aligned the radio and it works great now. Thanks!
- Texasrocker - 08-09-2008
...glad you bent those tube pins for good connection! I forgot to mention that! The best way to "clean" the tube pins on loctal tubes, is by actually hand-scraping each individual pin with a exacto-knife blade till "shiny".
Most usually, wire brushes, emory cloth, dont have enough cleaning power when dealing with those type tubes! It takes "force" to get those pins clean(scraping) again for proper contact with the loctal-sockets! It is also a good idea to spray WD-40 on both the tube pin tips , and sockets to keep the loctals-connections (all) from corroding again in the near future, or they will in high-humidity type climates! You bet, bad tube design invention from the get-go,period!!
Anytime you have a prob with any radio using loctal-type tubes after full re-cap, most usually, the residual probs of alignment or etc, can be traced back to the loctal tube design!
Ive been told by several WW2 USAF radio-techs, that the loctal-type tubes were originally designed by "JAN" ( IE: joint Army/NAVY) to be used in the WW2 era aircraft Radar systems,etc, and lots of them failed at very in-opportune times of warfare!! Im sure lots of Radio mfgrs of that era snapped the leftover JAN type loctal type tubes up to be used in "receivers" only for a very modest/ quantity price back in those days to be used in home type radio receivers! Zenith also used lots of the loctal type Govt leftovers in their production runs of tube radios also, as well as most other mfgrs! Now, all us vintage radio techs get to deal with them!!