[Milsurplus] FT-241 crystals question

Sun Jan 11 16:45:44 EST 2026

Wayne, thank you!

Sent from my iPad

> On Jan 11, 2026, at 15:37, hwhall at compuserve.com wrote:
> 
> There's multiple failure modes. The wires from pins to quartz slab corrode or break. The welded connection of the wires to the slab break off. Some maybe just quit due to outgassing contamination of the slab. And I wonder how many are solder failures in the pins (sometimes we see that in tube pins). The FT-241 was not a very physically robust design. The consensus is that they were not really repairable, but as always, that depends on the failure & the ingenuity & persistence of the owner.
> 
> Wayne
> WB4OGM
> 
> On Sunday, January 11, 2026 at 02:19:54 PM MST, Francesco Ledda via Milsurplus <milsurplus at mailman.qth.net> wrote:
> 
> What is the failure mode of these FT-241 crystals? Are they repairable?
> 
> Thank you, Francesco K5URG
> 
> Sent from my iPad
> 
>> On Jan 11, 2026, at 15:03, Al Klase <ark at ar88.net> wrote:
>> 
>> 
> Dave,
> 
> You're right.  The crystal-lattice filters were the primary ham use.  But, I did use a 518 KHz unit for a simulated Slaby-Arco alternator CW transmitter in a demo I built for our Museum https://rtm.njarc.org/ to give visitors a feel for what Sarnoff heard when Armstrong demo'ed his regen receiver at our site (Marconi Belmar, NJ) in 1914.  VIDEO HERE.
> 
> 73,
> AL
> 
> 
>> On 1/11/2026 1:52 PM, Dave Merrill wrote:
>> 
>> 
>>   
> 
> 
> Aside from the few frequencies around 455kHz that were adapted for sideband filters, what utility did any of the FT-241s have beyond their original military use?
> 
> 
> 
> 
> --... ...-- Dave N9ZC
> 
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> 
> On Sat, Jan 10, 2026 at 5:58 PM hwhall--- via Milsurplus <milsurplus at mailman.qth.net> wrote:
> 
> 
>> They are spiffy-looking though. :-)
>> 
>> Wayne
>> WB4OGM
>> 
>> On Saturday, January 10, 2026 at 04:29:59 PM MST, John Vendely <jvendely at cfl.rr.com> wrote:
>> 
>> Back in the late 60s, Esse Radio in Indianapolis had bins full of FT-241s for a dime each, and in those days, it was rare to find a bad one.  It's true that today, a good 50% of them have failed.  Some have obvious problems like detached or corroded bond wires, whereas the quartz elements of others seem to have mysteriously lost "activity".  A few years ago a couple of us decided to fire up the old SCR-508s and 608s.  Just for a laff, I tried opening some failed FT-241s, and if they were mechanically intact, ultrasonically cleaned them.  To my surprise, some came back to life.  Occasionally, you can still find individual FT-241As in sealed foil bags, and these have a much lower failure rate.  In any case, other than for use in the original radios, the FT-241 has essentially no utility today.  
>> 
>> The FT-241 was an unusually difficult crystal to produce, requiring state of the art techniques.  There were multiple attempts at setting up second-source FT-241 manufacturers, but none succeeded.  Only its developer, Western Electric, was ever able to mass produce FT-241s.  An FT-241 production line was built at ITT which showed some promise, but the war ended before it produced usable crystals in quantity, and the effort was terminated.  
>> 
>> For the truly hard-core who really appreciate this stuff, there's a very interesting and lengthy chapter with detailed technical info on Western Electric's complex FT-241 production process in the book "Quartz Crystals for Electrical Circuits" by Heising.  
>> 
>> 73,
>> 
>> John K9WT
>> 
>>> On 1/10/2026 3:41 PM, Hubert Miller wrote:
>>> 
>>>   
>> These FT-241 LF rocks have a fail rate somewhere between 40 and 70%. Seeing that myself, dissuaded me from keeping any of them. I believe the only people who might want them are the vehicle militaria collectors. 
>> 
>> I have not myself seen any article on how to bring them back. Maybe two tiny pressure point contacts, that might get some resonant activity, but there's no longterm fix i know of. 
>> 
>> The 'Boatanchors' ham radio group a decade or so back, had a mass dispersal of an FT-241 lot someone had found. Known as "The Great Crystal Caper". I was sobered by the miserable results testing the crystals, and i wrote off keeping any of those series. 
>> 
>> -Hue Miller
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> --
> 
> ARK Sig Block
> Al Klase - N3FRQ
> Jersey City, NJ
> http://www.skywaves.ar88.net/
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