The AM Forum

Receivers having the small can 3/4" square IF cans can have mica disease. The older 2" square IF cans do not have mica disease. Small can IF started to show up around 1952. Large can IF were used in receivers till 1960. The small can IF fix is extensive and one has to experiment for replacement mica capacitor value.
IMO it is not worth buying a small can IF receiver. The Hammarlund HQ-129, HQ-140X and HQ-150 are great receivers with large can IFs. The forementioned Hammarlund are as good as a Collins 75A4 on AM per boat anchor receiver tests here: https://w1vd.com/BAreceivertest.html

Trolling for more support for your flag raising mica disease!
You have a similar thread running on QRZ: https://forums.qrz.com/index.php?threads/receivers-with-if-mica-disease.937926/

Like lots of other aging stuff, things fail, and need to be fixed or replaced. Boatanchor radio equipment are no different. If equipment or part failure bothers or annoys you, get a modern plastic radio. In time, it ages too and parts problems will pop up. OR, find another hobby.

Over the years, I've had many boatanchor receivers from National, Hammarlund, Hasllicrafters, etc. and many had parts problems but none of them ever had a mica disease problem.

McIntosh audio used similar IF cans in their 60s and 70s FM stereo tuners and receivers and suffered the same malady over time.  I used to work for a McIntosh service center and would rebuild those IF cans pretty much the same way N8VIL demonstrates in his video on QRZ. It's not rocket surgery and takes time and patience but more importantly the right tools, steady hand and technique. It's almost like being a watch maker.

QRZ is a different forum, why should not post here. Despite your all receivers are fine, they are not and IF can rebuild is a huge task.

Trolling? This is a different forum than QRZ. IF mica disease is real despite you stating all receivers are fine.

People troll another website when they don't get the answer they want on other websites.

Would it still be called 'trolling' if they never got any answer off other websites?

I know that people can make decisions by 'consensus' when they ask a question then 7 answers show up.
What usually happens is 3 answers are obviously wrong...the other 4 more or less agree with each other.
Then the asker thinks that...'well, 4 of them are close so that must be the answer.'
Only problem is....all 7 are wrong.

I don't troll very often but when I do it's for Walleye.

73 N8QPC

This post has nothing about getting right answer on QRZ, it is about informing Hams.

My post has nothing to do with QRZ post. It has nothing to do with getting right or wrong answers on QRZ. It is about informing Hams on this forum.

And after all the hundreds of "mica disease" threads/posts on all the various message boards over the last ten years or so, you think its imperative to post yet another missive regarding, "the sky is falling", as if it were a NEWS flash? 

You're right, doesn't have anything to do with QRZ or the AM forum, nor any other forum for that matter, I think it's simply trolling for attention. 

With Jim's depth and breadth of boatanchor knowledge, he has become a 21st century Carnac the Magnificent!

Pete, you know way more then I.

BUT as Carnac the Magnificent, you have psychically magical boatanchor insight into unknown answers to unseen questions.

MikeKE0ZUinkcmo said:Suffice to say Mike, you nailed it!

This greatly overblown "mica disease" tripe is apparently the sequel to the equally ridiculous "6146 family of tubes" crap that like a horror movie villain just refuses to die.

Rodger WQ9E

Let me pick your memory bank here..

I have a MAC1700 receiver I acquired in 1987. It's a '70s piece.  It stays on 24/7 in my office, although I had to replace the power supply caps a few years ago.  The FM reception is pretty weak. Would this be a unit that would suffer from problems inside the IF cans? If so, can you give me some idea of the necessary work and how to tell if it's the problem?

Ed

You say: FM reception is weak. What type of antenna are you using?

Ed,
Wow.  We're going back 30 plus years and memory is hazy but it's hard to say if the IF cans are the cause without doing some testing. It's very possible given the age. Back then, majority of weak performance was due to weak tubes in the rf amp, LO and/or mixer. Swapping tubes usually fixed things and maybe a minor tweak of the front end to peak things especially getting the LO on target so the dial pointer was where it needed to be.  Either way would require using test gear to make the right decision and course of action. But again we're going back 30 or more years. Time is not on the IF can side. also weakness could be a combination of those things.

Bob
rkw

Absolutely, completely and totally true.
Now that the '6146 white paper' is not posted on every worldwide forum and list server several times a year.....hopefully that nonsense will eventually die out.
It's worth reading though just to see the one liner that explains everything and the reason why the originator almost 'lost his Motorola repair facility certification'.

I was thinking Mica Disease was what killed off the Sheriff on Gunsmoke... ;)

73DG

Wasn't Micah the sheriff in The Rifleman?

Naaa...that was Kitty Litter.
Mica Disease just worked the floor in the Long Branch.  :o

Gunsmoke, com on man! You think we are all like Joe Biden old? I always thought that receiver Mica disease was a subset of Industrial disease, at least a Dire Straits reference is twenty years more relevant.

And I thought that Festivus was the birthday of Festus.

KLC

Micah?  Wasn't he the guy that rode the boat ashore??  Or maybe that was "rowed the boat ashore"?  Yes, I think that is how the song goes.....

So many off-topic comments I almost totally forgot the topic at hand.   Oh yes, "Don't feed the troll".  No comments, the troll dies.  Simple enough concept.

mica disease is really silver disease if that is what is on the mica wafers.

Now just hold on a dawggone minnet!!!
Just cuz I know who Kitty Litter was don't mean I'm a hologram beamed out a basement window like some other geezer I heard of....jeeeze...

Correct. Mica caps without silver do not fail.

Not really a true statement!

Yes, mica capacitors, even silver mica capacitors, can fail, although they are generally considered very reliable components due to their stable construction, but factors like aging, manufacturing defects, or extreme environmental conditions can lead to failure. Extreme temperatures or humidity can also affect the performance and lifespan of a mica capacitor. Poor quality mica or improper manufacturing processes can lead to weak or inconsistent capacitors.

Mica capacitors, specifically "silver mica capacitors," are still manufactured today and are used in applications where high stability, low loss, and precise capacitance values are required, particularly in high-frequency circuits like RF transmitters and high-voltage applications due to their excellent electrical properties; however, "clamped mica capacitors" are considered obsolete due to inferior characteristics compared to silver mica capacitors.

These encapsulated silver mica capacitors generally are considered quite reliable. I have bags of these caps at various capacitance and voltage that were manufactured in the 60's and still hold their accuracy and performance today.

(https://madpcb.com/wp-content/uploads/2020/11/Silver-Mica-Capacitors.jpg)

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HOWEVER: the open-construction of silver mica capacitors in IF transformers can be very problematic given the right environmental conditions.

  Yes, I keep a stock of those around, and I've built some impressively stable VFO's with them. Nice parts. Will they still be working as well in fifty years? Probably, but I suspect I'll have moved on to other things by then.

You might be seeing the effects of bad silver-mica capacitors. Apparently silver can migrate thru the mica insulation forming little fingers (dendrites) which can intermittently short the capacitor, cause capacitance changes, and/or affect the capacitor's Q.

I had read this before so I asked the great Karnac ' Google

Johnathan N8QPC