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Re: S-40 Drifted Micas
¿ªÔÆÌåÓýMike, ? Had a look at your QRZ page ¨C you have a great collection of boat anchor awesomeness!? Like you, my restoration work is to keep me busy and out of trouble.? Based on the experience with the S-40, I¡¯m going to have to revisit some of my favorite old receivers here and have a closer look at the micas.? That would include the micas in my HRO-60 and its coil packs (some of which lack sufficient sensitivity).? I occasionally write articles for ER magazine -- in light of all this, I¡¯ve saved the micas, will cut them open, and write something up.? I think the time has come to dispense with the notion that the antique micas are generally infallible. ? 73 ¨C Steve, KW4H ? From: <[email protected]> on behalf of Mike <w5cul@...> ? Steve, ? I have been working on these old radios off and on for many years, I just enjoy restoring the occasional old tube radio that peaks my interest.? And besides it keeps me busy and out of trouble.? As you said, when it comes to the Mica¡¯s in those old tube radios, the word from those who have doing this a lot longer than me has always been do not waste your time with replacing the older rectangular encased (Domino) Micas, they are good.? Then this email thread pops up with some extremely knowledgeable gentlemen pitching in on the discussion with their findings as of late.? What made me stand up and take notice was the comment that one of those gentlemen made.? Not sure of the exact wording but the intent of his messages struck me in the head like a shalalie.? He indicated that yes the rule of thumb was do not bother replacing the old Mica¡¯s, and that it was good advice back then as they have been burned in and will not drift outside of their rating.? However, he went on to say something about that advice is now over 40 to 50 years old, and as such is not good advice any longer.? This made me think of a radio that was built in the 1950¡¯s, those micas in that radio have been around for over 70 years now, thus are now extremely suspect for all the varying reasons that others have pointed out and discussed in this thread.? So I am not afraid to admit it, this has been an eye opener for me as I guess I have been programed such that when I see one of those Domino Mica¡¯s, I just arbitrarily skip over it.? Well, that is not going to happen any longer.? Guess I better increase my inventory of Dipped Silver Mica¡¯s and get to soldering. ? Thank you, ? Mike W5CUL ? From: [email protected] <[email protected]> On Behalf Of KW4H via groups.io
Sent: Thursday, September 29, 2022 9:13 AM To: [email protected] Subject: Re: [HallicraftersRadios] S-40 Drifted Micas ? All very interesting info.? Well, one thing is absolutely for certain:? the days of ¡°don¡¯t touch that mica!¡± are over with (for me, anyway).? The drumbeat has been broken.? On forum after forum you¡¯ll find comments from longtime experts who claim, with a wave of their flux-stained fingers, that replacing micas is a ¡°waste of time¡± and the ¡°work of the inexperienced¡±.? Well, I¡¯ve got a collection of micas right here that proves that position wrong ¨C and there are probably even more if you count the micas I ignored in a couple of other projects this year.? ? ? 73 ¨C Steve, KW4H ? From: <[email protected]> on behalf of "D. Platt" <jeepp@...> ? My experience indicates a crap-shoot very often. One Hallicrafters BC-669 required a 100% recap. Another one was fine. My S-40B "appears" to be still perking along. I did have a mica go out in a BC-348R in the LO box. It coupled the variable cap into the circuit. Compressed the tuning range and took a while to find the problem. An APR-4 needed 100% tiny mica re-cap. Very poor components.? Persevere!!! Jeep K3HVG
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