Quick Tech Tip Silver Mica Disease

[@garp32]

For the life of me, I never thought about using the noise function to find SMD. I've used it for noisy transistors and resistors.. duh.. this is a perfect application for that function. I'll try to remember that next time. Im sure you've seen Shango use night vision goggles to actually see the arcing going on. Just not everyone has night vision goggles laying around, but I have 3 signal tracers! Thanks for the tip, Sam!

[@oldavguywholovesRCA]

Your Welcome!

[@daleburrell6273]

...I have seen those Shango66 videos too...

[@Centar1964]

Thanks, I have the exact same signal tracer and never knew what the noise function was for.

[@lamontprospect9974]

I bought a 2022 Marshall 50 watt JVM amplifier for my guitar. And that's almost exactly the sound I was getting out of the amp when I turned it on after letting it sit for about a year. It took the engineer five weeks to figure out that it wasn't a tube or a resistor but a silver Micah capacitor that went bad. From what I've read those capacitors should last at least 10 years. Why the thing went out I don't know. In the 3 years that I had the amp it was hardly played. But now that the silver Mica capacitor has been replaced the amp sounds like brand new. The noise was so bad it sounded like 15 rabid raccoons fighting with a badger. 🙏😃🕊️❤️ That signal tracer looks like a good investment

[@kadyszrybak6280]

If capacitance is not shown on the schematic i disconnect one lead from the if coil and measure the capacitance before removing the capacitors . This way I don't have to guess . Another way is to measure inductance of the coil and frequency and I use formula to get capacitance that's easy found on line I use LCR-T4 checker . Checks capacitors and inductance

[@jimnewman5596]

Thanks for sharing that great tip.

[@radio-ged4626]

I like the description about it sounding like raccoons fighting for potato chips.

[@jimnewman5596]

The radio that I'm working on now has SMD and I used a low voltage leaky capacitor checker and a high voltage leaky capacitor checker, and both will conduct across the primary to the secondary of the IF showing SMD. Really cool. On the ohmmeter shows open.

[@hestheMaster]

Great video Sam.

[@outofround]

So, basically you're looking for leakage between the primary and secondary. I remember doing something like that when I worked for the DoD checking sonar cables with a Megger.

[@oldavguywholovesRCA]

Yep. Thanks!

[@Rekless70]

15 racoons fighting each other with a bag of potato chips. Suscribed!

[@daleburrell6273]

...how is it connected to the IF transformer? There's a coil in parallel with the capacitor...

[@kadyszrybak6280]

Why didn't you measure voltage coming from the noise generator , so you can tell what voltage is coming out ?

[@oldavguywholovesRCA]

Didn't need to do all that.

[@UpcomingJedi]

I suspect the noise in my s38e may be caused by morethan bad mica but due to dirty power in the new, poorly sheiled wire. On the other hand, the volume is very poor.

[@oldavguywholovesRCA]

Dirty tube sockets, noisy resistors, caps, etc can do that as well. Good luck. Thanks!

[@ericeric6342]

Is this common in 30s, 40,s 50s radios? Or is it specific to a certain decade?

[@oldavguywholovesRCA]

Common in the later sets when they started making table top stuff and miniaturizing or modernizing stuff.

[@johnblystone8781]

If the mica sheets can be removed from the IF transformer, can they somehow be cleaned to eliminate the noise?

[@oldavguywholovesRCA]

You cut them out and replace with a real capacitor, I will be making a follow up video in regard to this which shows the procedure.

[@daleburrell6273]

...it doesn't work that way-!

[@oldavguywholovesRCA]

what exactly doesn't work that way?@@daleburrell6273

[@UpcomingJedi]

@@oldavguywholovesRCA he means you cant just take out the mica and clean that silver off the sheets.

[@michaelredman5169]

For sets that don’t show the IF cap values, would it be possible to find the value by applying 455khz and trying different value caps to find the sharpest resonant peak? Once the micas have been removed of course..

[@oldavguywholovesRCA]

Thats one way to do it. This transformer performed perfect back in its habitat, but the 2nd transformer was a bit of a pain. I didn't show that one being reworked.

[@tommorrow1931]

do all the IF coils have silver mica on it, I have telefunken radio console, it is worth it to try to repair?

[@oldavguywholovesRCA]

Not all of them, only the newer stuff from I guess the late to mid fifties on up.

[@ghlscitel6714]

Is there a "medicine" for curing the disease?

[@oldavguywholovesRCA]

There is but nobodies been able to figure out where the mouth is yet.

[@twoheart7813]

I think my SX-71 suffers from that. The high band sounds like raccoons on LSD.

[@lamontprospect9974]

Why can't the raccoons stop fighting. Whatever happened to the brotherly love amongst raccoons. What happens is, they start fighting and the whole damn amplifier falls apart. 🙏🕊️❤️

[@oldavguywholovesRCA]

They are all masked bandits so they naturally don't get along :-)