Quote:
Originally Posted by falcon123
you have asked a lot of questions. the generator is set (kenwood sg5150) to 454.5kc which is the crystal frequency. i have also tried it at 455kc. the mvc is turned on so the avc is off.the hallicrafters manual stipulates that the set while designed at 455kc is aligned to exact crystal frequency which can be slightly more or less. the generator is connected to the low capacity gang directly and i set it for a minimum tone and back it it off as it increases during alignment. the procedure follows the hallicrafters service data NOT sam;s but in this area its the same. the caps you refer to 32-35 (sam's) c70.c55 (hallicrafters) are cornell dubilier poly axials are identical, installed the same as original, and are .01 mfd 630v. perhaps the item on the 2nd i.f. is defective? i did bake the extra transformer and re dip in bees wax after i finish my coffee this am i will have another go.i'm not sure how to check the 2nd i.f. for a different resonate frequency. if i merely tune the generator up and down to see if 2nd i.f. output increases i decrease the output from the 1st and 3rd. how would i isolate it?? anyway lets hope that the baked transformer fares better and failing that ,i will try another .01 cap, i noted NO corrosion in the 2nd i.f. by the way.
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Yes, sorry for bombarding with questions! Just trying to cover as many possibilities as I can, because I think you have us all scratching our heads here......
It all sounds as though you have perfectly restored the parts, and yet we are left with the puzzle of one half of the transformers resonating somewhere else than the IF frequency.
Can you find out a) if there is any resonance in the primary tuned circuit, and b) where that resonance is? I suspect you can do that by tuning the sig gen far enough to find any peak from that primary. When you do find a peak, you should be able to confirm its due to the primary coil by adjusting the slug and observing output falling either side of resonance.
I am wondering if this is a tolerance problem in the fixed capacitor tuning the primary coil? Are these original - or replaced with new?
We may not get an answer as to why the primary tuned circuit is off frequency - but the solution is fairly obvious: adjust that parallel fixed capacitor up or down in value until you have resonance in the middle of the adjustment range of the slug. Sometimes the quick and dirty solution is the best you can do.....
Richard