Silver mica disease
Popping, crackling from silver migration in Automatic Radio manufactured IF cans. This is a tutorial for those with knowledge of electronic restoration and soldering. Use at your own risk!! The Silver Mica caps that are epoxy coated almost ==never== fail. They come in brown, red, reddish brown, and blue epoxy coatings. The Military used a silver/glass mica too. Extremely reliable and stable, but a tad more fragile. They also had a very tight tolerance too. That brings us around to what is known as Sliver Mica Disease. The fixed mica caps in the slug tuned IF transformers have two capacitors formed by depositing silver in four areas on a thin piece of mica, two on each side of the mica. Each pair of "plates" thus formed makes one capacitor, electrically connected across one coil. Re: Silver Mica Disease. I had this problem on one of Howard's sets - a Zenith H-615, where the set would make intermittant loud crackling and crashing noises. It seems to be caused by silver migration on the IFT tuning capacitors, causing leakage between the anode winding and the grid winding of the next stage. Silver Mica capacitor Disease. The crashing thunderous roar on the AM bands. In some IF transformers there are integrated capacitors internal to the enclosure. These capacitors are parallel to the primary and secondary of the coils. The range of capacitance, from what I have seen, range from about 70pf up to 250 pf.
29 Apr 2016 dreaded silver migration disease. Radios of this vintage contain RF transformers with integrated silver mica capacitors in the bottom of them.
Silver Mica capacitor Disease. The crashing thunderous roar on the AM bands. In some IF transformers there are integrated capacitors internal These transformers contain capacitors made of silver film on a mica substrate. The silver is exposed to the elements, causing corrosion, and results in Silver Mica 8 Jan 2019 Silver mica disease is really silver migration and it typically occurs when the silver itself is exposed to humidity and there's a substantial DC 19 Jun 2018 Paper mica's used foil for the conductor inside, and the silver mica's used silver. They first came in what is called a "postage stamp" or "Domino
1 May 2014 The exposure of this fibrous mineral causes fatal diseases including lung Silver mining from Galena ore occurs in Colorado, Idaho, Utah and
Popping, crackling from silver migration in Automatic Radio manufactured IF cans. This is a tutorial for those with knowledge of electronic restoration and soldering. Use at your own risk!! The Silver Mica caps that are epoxy coated almost ==never== fail. They come in brown, red, reddish brown, and blue epoxy coatings. The Military used a silver/glass mica too. Extremely reliable and stable, but a tad more fragile. They also had a very tight tolerance too. That brings us around to what is known as Sliver Mica Disease.
The silver mica capacitor provides very high levels of performance with close tolerance values with low levels of value change with temperature. In view of its performance it was the capacitor of choice for many RF circuits like oscillators and filters where close tolerance and low drift were needed.
While trying to learn more about silver mica migration, I found this website with step-by-step photos on how to repair IF cans with silver mica migration. Photos show repairs to a couple types of cans, including one from a Zenith Trans-Oceanic T600. It turns out that this is "Silver Mica Migration" or what some call "Silver Mica Disease" ha ha. Essentially the silver has creeped out of the silver mica capacitor in the IF coil transformer (the square metal cans) and is wreaking havoc on the radio. The silver mica capacitor provides very high levels of performance with close tolerance values with low levels of value change with temperature. In view of its performance it was the capacitor of choice for many RF circuits like oscillators and filters where close tolerance and low drift were needed.
I have first-hand experience of the silver-mica disease in a 1950’s Zenith (Model H723Z) – see attached – I took these photos with the intent of writing an article myself (thinking this was an undiscovered issue!), then I came across the articles on the web…
I have first-hand experience of the silver-mica disease in a 1950’s Zenith (Model H723Z) – see attached – I took these photos with the intent of writing an article myself (thinking this was an undiscovered issue!), then I came across the articles on the web… The Silver Mica disease of the late '40s and through the '50s, caused by Silver whiskers migrating across the surface of the mica, was solved by switching to disc ceramic caps in the IF's. I've been restoring a Zenith G723 and have run into the infamous Silver Mica Disease on the FM band. like in most cases I've read about, the mica caps in the IF cans are unlabeled. Anyone have ideas on what the values could be? I'm also having trouble locating which IF can the issue resides. Re: Silver Mica Disease. I had this problem on one of Howard's sets - a Zenith H-615, where the set would make intermittant loud crackling and crashing noises. It seems to be caused by silver migration on the IFT tuning capacitors, causing leakage between the anode winding and the grid winding of the next stage. While trying to learn more about silver mica migration, I found this website with step-by-step photos on how to repair IF cans with silver mica migration. Photos show repairs to a couple types of cans, including one from a Zenith Trans-Oceanic T600.
4 Jan 2018 Model: 500V 100pf 5% All in New condition never be used. Silver mica capacitors were commonly used in vintage Fender tube amplifiers. 29 Apr 2016 dreaded silver migration disease. Radios of this vintage contain RF transformers with integrated silver mica capacitors in the bottom of them. If your radio has this crashing sound on all bands and you have replaced the couplate, it is very likely that one or both of your IF cans has "Silver Mica Disease, " but 10 Apr 2019 I've heard of silver-mica disease. Much worse than component aging \endgroup – Zeiss Ikon Apr 11 '19 at 11:24. add a comment |