[fields 100]

That little thing gives me plenty of headache. After fixing the 6A8 tube (all contacts inside the base were loose, go figure),
alignment was an order of things. The set is very sensitive and receives many stations but all over the place with at least 20K.C. discrepancy, and that discrepancy is not linear.1500 is at 1200, 800 is at630, etc. The alignment procedure is written very laconically. So, first to k work with are 2 IF tr-rs, then the wave trap,after that 3 other trimmers, that takes care of BC alignment.All has been done,but even after that the same problem still persists.The only thing damaged in this set was the osc. coil, which I rewound with exact amount of turns observing correct rotation.The only difference- slightly thicker wire gauge.Did not touch any micas. One issue I had was the trimmer J - I was running out of capacity to the point that I almost cracked the porcelain base of it.It is about 390PF max. So, I added in parallel 40PF with no positive results.
Any ideas? Thanks.

http://www.nostalgiaair.org/PagesByModel...0025008.pd

[Radioroslyn]

Bad link.
Terry

[fields 100]

Sorry,

That PC has to go soon.

http://www.nostalgiaair.org/PagesByModel...025008.pdf

[Radioroslyn]

So how many turns did you have to rewind??
Terry

[fields 100]

67 turns CW facing the terminals ( CCW facing the mounting pins). The wire thickness was 0.03MM thicker than original, but it fitted nicely. I am quite sure the amount of turns is correct, I am using +10 magnifier with a pin counting, and to my bad luck every set I have (almost every one) needed the coil rewind, so I have some sort of experience in doing it.

[Radioroslyn]

Well whatever is going on you don't have enough turns on your coil to bring 800kc down to 600kc. So you could add some more turns until you the low end of the dial where it should be. I'd go with 15-20 turns till the low end is correct. Then you can see where the top is.
Terry

[fields 100]

Thanks Terry,

The thing is, that even with original thinner gauge an extra 15-20 turns would not fit onto the coil's tube.(And I doubt I could make such a gross error). What is happening (I think I did not explain the problem correctly) is that alignment went through just fine at both ends (600 and 1500). But then, the 800 station can be found at 630K.C. on the dial, 1200 station on 1500 and so on with a pointer installed correctly, line to the line. After that all I could do is just rock gang to increase capacity of the J trimmer to raise to pointer closer to the 800, but so far with the trimmer maxed out was able to bring only to 720.

[Radioroslyn]

So you  are telling me that 600kc is dead on but you move the dial 30kc and your sitting 800kc??
Terry

[fields 100]

Yes,that's right.

[Radioroslyn]

Well what will cause that situation is using the wrong size wire or not observing the original spacing of the turns on the coil. I made the asumption that the section of the coil that was rewound is  frequency determining. not so much feedback. This is critical it must be rewound exactly as original. If you are sure this is the case then listen to it another reciever or use a counter to see if the osc is doing what you experiencing. If this is the case then try reversing the the leads from the rewound section. Another thing is you may have a bad mica cap across or in series with frequency determining section of the coil.
Terry

[morzh]

If both end align and the middle is wrong it could mean the tuning capacitor geometry is wong.
Or better yet, could you swap the two sections? Are they different size?

[fields 100]

OK, here is what I have done so far.Connected the counter to the osc. grid, all stations across the dial show the frequency of them +455K albeit being incorrect on the dial. So, I assume, that oscillator works fine. Prior to that,The 600 and 1500 had been aligned as per instruction procedure. The pointer was set .At that point all stations were grossly off on the dial.To bring the pointer to at least close position to the station I had to readjust the trimmer J, subsequently moving away from alignment, but that was the only option I had at the moment, unless there are some other ideas. I did not open the antenna coil can yet. Is it possible someone had been working on it or replaced with the wrong one?

[mikethedruid]

Hi fields, I am a little hazy about what you said in your last post. What is the frequency reading +455 with the plates of the tuning cap fully open, and fully closed? If these correspond with the proper upper and lower frequencies of the receiver; and you are able to receive the expected local stations with the frequency from the oscillator reading properly, then the overall RANGE is now correct, which would seem to mean the inductance is correct. Is the problem that the stations in between the lowest frequency, and highest, are not spaced out correctly as you tune them ? Does there seem to be any pattern to this distortion ? Have you considered a mechanical source, a slightly bent plate on the tuning cap, or a dial drive problem of some type ? One trick I might try is to tune the radio by ear, using strong local stations at the top and bottom of the dial to set those, and see what happens in between. I hope some of these thoughts are helpful. (as I write this the nostalgia air site seems to be down, so I couldn't read the schematic. Had to do this off the cuff)

[fields 100]

Mikethedruid,

Thanks Mike,
To answer to you questions, +455 I get throughout the entire range. There is a pattern.The indicated frequencies on the dial are always less than the station frequency but it is worse at the lower end than at the higher.Of course, I can move the pointer, but it will look pretty odd, as the needle will look at 2 o'clock vs 3 (the right side of the dial) and 8 o'clock at the left vs 9. Bending the plates I simply do not know how, as I've never done it before, unless it is gone just by the seat of your pants. Changing the capacity of the J padder after alignment, as I mentioned before, helps to bring the pointer to where it should be but that works only between 600 and 900, then the discrepancy comes in play again,albeit not as pronounced.

[AI2V]

Connecting a counter to the grid of the oscillator is a definite NO NO!!!  What ever you use to make that connection will as capacitance and lower the frequency;  as soon as you remove the connection the frequency will go up.

You need to wind perhaps 10 turns of and small insulated wire to make a loop of about one inch;  that will be your counter pick-up.  Just put the loop around the tube (without shield) or put the loop in the general area of the oscillator coil.  Remember that the oscillator should be 455KC above the dial freq.

With your radical freq error between 600 and 800KC, that's not from an error in coil turns-  no way.  Look very carefully at the tuning capacitor plates;  they should be perfectly centered.  It sound like you have a near short in the tuning cap, most likely one of the outer plates.