The melting temp of the film can be simply checked with a piece of the film and soldering iron/oven.
As for sealing, parafin or as I used just recently, a conformal coating that is neutral to the wire lacquer, like acrylic or silicon.
I have used clear lacquer or clear nail polish to reseal coils, no problems yet with wither one.
I would not use wax (paraffin) as you would just be re-creating what caused the problem in the first place. It was thought at the time that wax would keep moisture out. What happened was, it not only allowed moisture in, but it also held it in.
I have a question about replacement of the 5 capacitors inside the metal box, 7A,B,C,D,E. Shall I assume these are shielded inside the metal box for a reason?
Instead of running all the wires back to the metal box, why can't I just solder in replacement capacitors near their connection points with the other end of each going to the nearest ground point?
Thanks,
Mark
(03-07-2015, 10:19 PM)markmokris Wrote: [ -> ]I have a question about replacement of the 5 capacitors inside the metal box, 7A,B,C,D,E. Shall I assume these are shielded inside the metal box for a reason?
Instead of running all the wires back to the metal box, why can't I just solder in replacement capacitors near their connection points with the other end of each going to the nearest ground point?
Thanks,
Mark
Mark,
Yes it is possible and I do not think the can is intended as a shield.
However, if you solder caps to nearest GND you may or may not have GND currents and so some extra noise.
Not necessarily, quite posible it might be just fine.
There is even a chance it will work better as then you need no long wires for some caps which are inductive and so themselves defeat some capacitance and introduce extra noise. The experiment will show if it is better, worse or the same.
I have a new question.
I replaced the two electrolytics in the power supply with 10uf 450V modern ones that I had on hand. With power on, the radio definitely has a bit of 60 cycle hum. There is no signal coming through, so maybe it is normal in the background. Not sure.
I put a scope on the plus-side of the second electrolytic. There is about 295 volts DC with about 4 V ripple peak-to-peak. Would that be enough ripple to cause what I am hearing?
Is that outside of normal?
Mark
Should there be any need to add additional filtering over the field coil and 2 electrolytics in the standard design for this Model 19. It just seems like the background him seems a little excessive. Or maybe I have something else wrong?
Thanks,
Mark
You could probably go a little higher on the second cap (I.e #46, the one after the field coil). Have you finished replacing the rest of the caps?
(03-10-2015, 06:35 AM)PAradiogeek Wrote: [ -> ]You could probably go a little higher on the second cap (I.e #46, the one after the field coil). Have you finished replacing the rest of the caps?
No, I still have a couple bakelite blocks to replace. Could this be part of the problem?
Mark
It's possible. Also, when you are working in there try to maintain the same 'routing' for the wires.
What kind of mylar tape can I use for separating layers when rewinding coils, like the oscillator ticker coil? All the tape I see says "metalized". Is there really metal in the tape? Is there metalized and non-metalized?
Mark
Why is mylar?
What's wrong with Kapton? Especially that one that has high melting temp (not that this is too important when the coil is made on a new or a baked bobbin)?
The article I saw said "Use Mylar tape." What should I use? What is Kaplan?
Mark
Ok thanks for the tip guys. I just ordered some.
Mark
Mark
Kapton is 3M trademark, Kaplan is a jewish last name and the name of scolar preparatory courses.
Not quite the same.