05-02-2018, 07:27 PM
Skip,
I have "baked" other coils, in a Zenith T.O. a Hammarlund Super-Pro and a Grunow. All with good results, in fact for the Zenith and the Hammarlund, both radios were completely placed into the oven after removing all plastic and rubber parts, dials, speaker, etc. They were in the oven until the wax started to flow. The concept was to drive out any moisture in the coils and raise the "Q". No resistances were taken as I did not expect them to change. What I expected and what happened was a much sharper response in alignment a noticeable increase in sensitivity.
For the Grunow the oscillator coil was fully re-wound for the BC/Police band, completed coil was immersed in hot bees wax and placed under vacuum for about 30 minutes until all bubbles ceased, vacuum release, coil set aside to cool, coil returned to hot wax for two quick wax coating dips. Radio aligned, coil was no more than 1/2 turn on alignment screws, worked perfectly.
What happen during the rewind of the Grunow was the removal of a cellulose acetate primary/secondary liner and replaced with thin plastic film. It was that liner than caused corrosion to the primary, the bottom layer.
I do not advocate placing an entire Philco chassis into an oven because a chassis may have coils wound with the cellulose plastic liner. Cellulose acetate is very flammable, that could be a disaster!
As for a rewound coil as long as the liner is gone then heating in an over for the 1/2 hour would seal the windings with the remaining wax and drive out any moisture in the entire assembly. IMHO that is a good thing.
YMMV
Chas
I have "baked" other coils, in a Zenith T.O. a Hammarlund Super-Pro and a Grunow. All with good results, in fact for the Zenith and the Hammarlund, both radios were completely placed into the oven after removing all plastic and rubber parts, dials, speaker, etc. They were in the oven until the wax started to flow. The concept was to drive out any moisture in the coils and raise the "Q". No resistances were taken as I did not expect them to change. What I expected and what happened was a much sharper response in alignment a noticeable increase in sensitivity.
For the Grunow the oscillator coil was fully re-wound for the BC/Police band, completed coil was immersed in hot bees wax and placed under vacuum for about 30 minutes until all bubbles ceased, vacuum release, coil set aside to cool, coil returned to hot wax for two quick wax coating dips. Radio aligned, coil was no more than 1/2 turn on alignment screws, worked perfectly.
What happen during the rewind of the Grunow was the removal of a cellulose acetate primary/secondary liner and replaced with thin plastic film. It was that liner than caused corrosion to the primary, the bottom layer.
I do not advocate placing an entire Philco chassis into an oven because a chassis may have coils wound with the cellulose plastic liner. Cellulose acetate is very flammable, that could be a disaster!
As for a rewound coil as long as the liner is gone then heating in an over for the 1/2 hour would seal the windings with the remaining wax and drive out any moisture in the entire assembly. IMHO that is a good thing.
YMMV
Chas
Pliny the younger
“nihil novum nihil varium nihil quod non semel spectasse sufficiat”
