November 21, 2016 at 4:36 pm #8235KyleForum Participant
I’m restoring a Westinghouse model 99. Replacing the caps and resistors. One mica cap has been replaced in the past. I’m thinking about replacing all of them just to be safe. I have the mica values that I need but I have no info on what voltage rating they are. The Westinghouse manual called them toothpick condensers and they are thin. Is there a way to find out what the voltages are?November 21, 2016 at 5:40 pm #8238Jerry TombariForum Participant
My advice would be not to replace the mica caps. Who knows why one was replaced. It could have been on spec. I have been doing this for three years now and have never replaced one. Get the radio working and then worry about it. I would also analyse the schematic and try and figure out what the voltages could be.
Good luckNovember 25, 2016 at 2:00 pm #8252philForum Participant
i’ve bought caps in the picofarad range from lees electronics. as I recall they were 650V ones I think they had a high enough rating but from all I have heard I agree with Jerry. they usually don’t’ fail and if they do you can probably get a replacement or perhaps steal one from another radio.
the ones you have, do they look like dominoes?November 25, 2016 at 2:16 pm #8253philForum Participant
also its a little off the original topic but you may notice the tuning condenser has some plates bent away. they are sort of segments with slots cut in them. as I recall there were some procedures to tune them by bending the plates which affected the capacitance of the tuning condenser as part of alignment. So I’d just say if you notice this don’t assume they were bent out of plane by abuse they may be tuned this way. I don’t mean tuning condensers with close fitting plates which are touching and grounding out the tuning condensor. that condition is different as if they actually touch it will kill the signal. sometimes the core of the tuning cap was cast from a lead alloy over time it can sometimes take on water and expand ( slightly distort) and thus throw off the alignment of the plates. also you may find some square metal cans under the chassis that are in fact paper capacitors in square metal cans and not necessarily electrolytic caps. I seem to remember replacing the guts with orange drops or mylars but at first glance thought since they were in metal cans they might be electrolytic ones. there is likely room to replace what you want underneath without worrying about space constraints so you might be able to keep those in place and if you want o replace just put the new ones beside them if you don’t want to re-stuff them.November 26, 2016 at 11:39 am #8262KyleForum Participant
Thanks for the replies. No the mica caps do not look like dominoes. They are thin and long about 2 inches. No markings. copper casing with one side open.
I did take a look at this tuning cap when I was taking apart the radio. all the plates were straight. My morconi had one just touching, readusted that one and has been working great since If Im right by the service manual there are no wet caps. I’ve took apart most of the cap cans which contain 3-5 caps are all wax filled paper caps.
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