Posts: 228
Threads: 64
Joined: Dec 2013
City: Northbrook, IL
I suspect that one of my coils has short in the winding.It is the secondary RF transformer coil going to the control grid of the RF tube.To get correct alignment, I have to completely unscrew the tuner's compensator adjustment nut, set it aside and bend out the upper copper plate (just totally delete the said compensator). At that point the VTVM shows the peak, but I hate the look of it without that nut and the plate hanging in the air like that.
So, it might be the coil. Both coils show continuity, one coil shows resistance, another is not, however it looks like it has very low winding count.
Should I just go ahead and rewind both of them or is there some other way to
verify?
Thanks.
Posts: 15,305
Threads: 530
Joined: Oct 2011
City: Jackson, NJ
What coil is this?
If this is an oscillator coil, had it gotten any shorts your oscillator would not oscillate, let alone at the right frequencies or close.
If it is an IF......maybe, but still a short is a short and you probably would have an extremely quiet reception or none depending if it is an output or input coil.
I mean, if you are mentally at the point where you could rewind it, sure do, but it is a job requiring some effort and I usually try to prove to myself I need to do it before I yank out a coil. I hate rewinding.
Posts: 228
Threads: 64
Joined: Dec 2013
City: Northbrook, IL
@Morzh
It is a RF coil. Mentally..? I do not know...Might need few sessions to feel adequate for such endeavor.
But jokes aside, do you think my reasoning makes sense? I am talking about that compensator with completely loose copper plate.
Posts: 15,305
Threads: 530
Joined: Oct 2011
City: Jackson, NJ
Fields
What radio?
Link to the sch?
Etc?
Posts: 228
Threads: 64
Joined: Dec 2013
City: Northbrook, IL
Morzh
That was a general question. RF transformer/tuner with adjustable compensator. As I mentioned earlier, had to delete compensator completely to achieve max. output. Suspect the coil.
However.. here it is:
http://www.nostalgiaair.org/PagesByModel...013881.pdf
(This post was last modified: 05-22-2014, 03:35 PM by
fields 100.)
Posts: 1,113
Threads: 14
Joined: Feb 2013
City: Irvington, NY
I doubt there is anything wrong with the RF coil. If the coil were to have shorted turns, the inductance would decrease not increase. Therefore you would need more compensator capacity, not less.
Is there anything else connected to the RF coil tuned circuit which would increase the stray capacity?
The other possibility is that the oscillator is running a higher freq than required to track the RF stage. You might try increasing the capacitance of the osc high freq compensator slightly. This would require you to tune the same station in with less tuning cap capacity, which would correspondingly reduce the RF stage tuning capacity. Then the RF compensator could be reassembled adding a small additional capacitance to achieve resonance.
Posts: 15,305
Threads: 530
Joined: Oct 2011
City: Jackson, NJ
You know...it is the RF coil....the second half of the antenna coil, right, going to the very first 24?
What alignment are we talking about, the band, right? Not the oscillator?
Then has it occur to you that your dial might simply be in a wrong position and the capacitance is already more than it should be?
Posts: 228
Threads: 64
Joined: Dec 2013
City: Northbrook, IL
Yes, it is antenna coil. Dial is at 1400kc.Sig. gen at 1400kc. HF osc. aligns OK with it's compensator.. Next is 1st det. at 1400kc-OK. Then 2d antenna- that is where the issue is. Deleted that compensator. Without compensator alignment is OK. The dial still at 1400kc. Next is 1st antenna-aligns OK. Even if the dial was in the wrong position, which I do not think it is, why then 3 other compensators allowed adjustment at 1400kc being fed from the generator with the same dial setting?
Posts: 228
Threads: 64
Joined: Dec 2013
City: Northbrook, IL
@ Mondial,
Interesting idea, it might work.So, when I detune (increase HF osc. compensator capacitance),should I chase 1400kc from generator by means of moving the dial away from 1400kc setting until I get the highest output on my meter?
Posts: 1,113
Threads: 14
Joined: Feb 2013
City: Irvington, NY
Yes, that's basically it. Increase HF compensator slightly and retune dial up for max signal. Then repeak ant and RF compensators for max. Hopefully now the problem compensator can be restored to normal condition. If still not sufficient, repeat procedure.
