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FW: FT-241 LF Crystals as a Long - Term Investment Instrument

Hue Miller
 

I had this bag of those WW2 FT-241 LF crystals, which were used in the WW2 era FM  and ship radios.

I realized I needed to finally make an executive decision on it, so I tested them all. I used the little Chinese

crystal tester I bought off Ebay for $12 or $18. I connected a couple alligator leads to the LF crystal connection

points on the tester.

Result: 74 defective, 13 working = 85% fail rate.

I did find one possibly good frequency, 457 kHz, but – for how much longer ?

Well, this kind of ends any fascination with possible uses of the LF FT-241s for me.

-Hue

Colin_Tuckley
 

On 06/11/2019 03:25, Hue Miller wrote:
I had this bag of those WW2 FT-241 LF crystals, which were used in the
WW2 era FM  and ship radios.
Result: 74 defective, 13 working = 85% fail rate.
Those crystals need a *lot* more drive than modern ones. Your little
Chinese tester may not be able to provide enough drive.

73, Colin

--
Colin Tuckley | +44(0)1223 830814 | PGP/GnuPG Key Id
G8TMV | +44(0)7799 143369 | 0xFA0C410738C9D903

Henk_Parasetguy
 

Hi Hue

Interesting conclusion. Did you open some up to see what caused the problem? The casings have rubber seals, perhaps something similar as what happened to old vibrator cans happened: the contact points corroded due to the rubber fumes.

Cleaning could help. Would be interesting to look inside.

 

 

Kind regards,

Henk - Parasetguy

http://www.paraset.nl/index.htm

http://www.paraset.nl/hut12_warehouse/index.htm

 

 

 

Van: wireless-set-no19@groups.io <wireless-set-no19@groups.io> Namens Hue Miller
Verzonden: woensdag 6 november 2019 4:26
Aan: armyradios@...; wireless-set-no19@groups.io
Onderwerp: [wireless-set-no19] FW: FT-241 LF Crystals as a Long - Term Investment Instrument

 

I had this bag of those WW2 FT-241 LF crystals, which were used in the WW2 era FM  and ship radios.

I realized I needed to finally make an executive decision on it, so I tested them all. I used the little Chinese

crystal tester I bought off Ebay for $12 or $18. I connected a couple alligator leads to the LF crystal connection

points on the tester.

Result: 74 defective, 13 working = 85% fail rate.

I did find one possibly good frequency, 457 kHz, but – for how much longer ?

Well, this kind of ends any fascination with possible uses of the LF FT-241s for me.

-Hue

Pete_G4GJL
 

Hue, dont give up entirely....

If Im not mistaken, the ebay cyrstal tester has a specification for its working frequency range, limited principally by the feedback network.

If you were to build a low frequency oscillator, specifically for the job, you might well get a much higher 'success' rate. I think c.450kcs is too low for the circuit used.

A quick rough and ready test is to place a crystal in series with the aerial lead to a receiver set at the crystal frequency. You should hear a peak in received noise at the sharply defined crystal resonance.

From a similar batch of 20 or so I have here, two fail to oscillate. On inspection both failed ones had been screwdrivered....one by me 40 years ago!

I hope this helps save 74 innocent crystals from landfill!

73

Pete
G4GJL

On Wed, Nov 6, 2019 at 7:57 AM Hue Miller <kargo_cult@...> wrote:

I had this bag of those WW2 FT-241 LF crystals, which were used in the WW2 era FM  and ship radios.

I realized I needed to finally make an executive decision on it, so I tested them all. I used the little Chinese

crystal tester I bought off Ebay for $12 or $18. I connected a couple alligator leads to the LF crystal connection

points on the tester.

Result: 74 defective, 13 working = 85% fail rate.

I did find one possibly good frequency, 457 kHz, but – for how much longer ?

Well, this kind of ends any fascination with possible uses of the LF FT-241s for me.

-Hue

Henk_Parasetguy
 

Hi Pete, Hue

 

Good to know this, as I also bought such a cheap tester from a Chinese site.

Before that, I tested xtals on my grid dipper in combination with a freq. counter.

I modified the dipper according to this diagram:

https://www.paraset.nl/_downloads/xtals%26dipper/MEASURING%20XTALS%20WITH%20A%20DIPPER%20AND%20COUNTER.pdf

So far that worked well for FT-243 and FT-171 rocks.

 

Kind regards,

Henk - Parasetguy

http://www.paraset.nl/index.htm

http://www.paraset.nl/hut12_warehouse/index.htm

 

 

 

Van: wireless-set-no19@groups.io <wireless-set-no19@groups.io> Namens Pete_G4GJL
Verzonden: woensdag 6 november 2019 10:54
Aan: wireless-set-no19@groups.io Notification <wireless-set-no19@groups.io>
Onderwerp: Re: [wireless-set-no19] FW: FT-241 LF Crystals as a Long - Term Investment Instrument

 

Hue, dont give up entirely....

 

If Im not mistaken, the ebay cyrstal tester has a specification for its working frequency range, limited principally by the feedback network.

 

If you were to build a low frequency oscillator, specifically for the job, you might well get a much higher 'success' rate. I think c.450kcs is too low for the circuit used.

 

A quick rough and ready test is to place a crystal in series with the aerial lead to a receiver set at the crystal frequency. You should hear a peak in received noise at the sharply defined crystal resonance.

 

From a similar batch of 20 or so I have here, two fail to oscillate. On inspection both failed ones had been screwdrivered....one by me 40 years ago!

 

I hope this helps save 74 innocent crystals from landfill!

 

73

 

Pete

G4GJL

 

 

 

Jacques_VE2JFE
 

Hello Henk,

 

To test crystals, I use the same setup (Kenwood DM-81 grid-dip model) except that I take the output going to the frequency meter from the RCA socket of the “probe”.

I use a short length of RG-62A/U to minimise the cable capacitance.

The main tuning capacitor can be used to check if the exact crystal frequency can be obtained by adjusting the loading capacitance.

I have also made adapters to test HC-6 and smaller crystals.

 

73, Jacques, VE2JFE

Andy_G8JAC
 

The old “standard” for crystal testing was the Test Set AM193 made by GEC.  It displayed the Equivalent Parallel Resistance which was used as a measure of crystal activity.

Both the army and RAF used them and there were commercial versions. 

I still have one in the shack although not much cause to use it recently.

 

Andy  G8JAC

 

 

 

>Hello Henk,

 

>To test crystals, I use the same setup (Kenwood DM-81 grid-dip model) except that I take the output going to the frequency meter from the RCA socket of the “probe”.

>I use a short length of RG-62A/U to minimise the cable capacitance.

>The main tuning capacitor can be used to check if the exact crystal frequency can be obtained by adjusting the loading capacitance.

>I have also made adapters to test HC-6 and smaller crystals.

 

>73, Jacques, VE2JFE

_._,_._,_

Chris_Jones
 

On Wed, Nov 6, 2019 at 03:18 PM, Andy_G8JAC wrote:
The old “standard” for crystal testing was the Test Set AM193 made by GEC.
As chance would have it the EMERs for the above were added to the Archive on 30th October. Document Requests are "off" at the moment but normal service should be restored sometime late tomorrow (8th November)

Chris / G8GFB

Henk_Parasetguy
 

Hi Jaques

I have a handful of different xtal sockets to make an universal adapter, but did not come to that, yet. The one with the alligator clips does it all the time, so ……..

 

 

Groet,

Henk

 

 

 

 

Van: wireless-set-no19@groups.io <wireless-set-no19@groups.io> Namens Jacques_VE2JFE
Verzonden: woensdag 6 november 2019 15:31
Aan: wireless-set-no19@groups.io
Onderwerp: Re: [wireless-set-no19] FW: FT-241 LF Crystals as a Long - Term Investment Instrument

 

Hello Henk,

 

To test crystals, I use the same setup (Kenwood DM-81 grid-dip model) except that I take the output going to the frequency meter from the RCA socket of the “probe”.

I use a short length of RG-62A/U to minimise the cable capacitance.

The main tuning capacitor can be used to check if the exact crystal frequency can be obtained by adjusting the loading capacitance.

I have also made adapters to test HC-6 and smaller crystals.

 

73, Jacques, VE2JFE

Chris_Suslowicz
 

Andy G8JAC wrote:

The old "standard" for crystal testing was the Test Set AM193 made by GEC. It displayed the Equivalent Parallel Resistance which was used as a measure of crystal activity.
Both the army and RAF used them and there were commercial versions.
I still have one in the shack although not much cause to use it recently.

I have a CT554 which may well be similar (they were manufactured by "Cimtel Ltd." who have vanished like so much on the UK manufacturing industries).

No manual, but it's reasonably obvious how to operate it.

(If anyone has a manual for it, I'd be interested in a copy.)

Chris (G8KGS)

Paul G8KFW
 

Hi chris

 

Just been looking for information on the Test Set AM193 made by GEC

And non found  interested to see a picture as currently looking for crystal tester

for to test my stock of crystals

 

Paul


From: wireless-set-no19@groups.io [mailto:wireless-set-no19@groups.io] On Behalf Of Chris_Jones via Groups.Io
Sent: 06 November 2019 15:41
To: wireless-set-no19@groups.io
Subject: Re: [wireless-set-no19] FW: FT-241 LF Crystals as a Long - Term Investment Instrument

 

On Wed, Nov 6, 2019 at 03:18 PM, Andy_G8JAC wrote:

The old “standard” for crystal testing was the Test Set AM193 made by GEC.

As chance would have it the EMERs for the above were added to the Archive on 30th October. Document Requests are "off" at the moment but normal service should be restored sometime late tomorrow (8th November)

Chris / G8GFB

No virus found in this message.
Checked by AVG - www.avg.com
Version: 2016.0.8048 / Virus Database: 4793/15886 - Release Date: 08/14/18
Internal Virus Database is out of date.

Chris_Jones
 

On Wed, Nov 6, 2019 at 03:18 PM, Andy_G8JAC wrote:
I still have one in the shack although not much cause to use it recently.
Well... an idea.

Would it be worth Hue posting you a few "suspect" crystals to see if they work when tested with it?

Having said that I checked the EMERs for the AM193 and the specifications state that it was for testing crystals from 3 MHz upwards, not "LF" ones. However it uses a Pierce circuit so I would expect that unless a crystal really is defunct then it should work.

Chris / G8GFB

Bob Burns
 

Hi Hue

I have found those crystals difficult to use with semiconductor circuits / oscillators but fine with valve based circuits. I have a Type 193A parallel mode crystal tester here if you are reasonably nearby (Coulsdon, North Surrey).

--
Regards

Bob

Bob F Burns

C Eng, FIET, MSE. G3OOU, @BobFBurns
Retired Electronics and Software Consultant
http://www.g3oou.co.uk/myexperience.html

Andy_G8JAC
 


>>Would it be worth Hue posting you a few "suspect" crystals to see if they work when tested with it?

 

Fine by me but ISTR that Hue is in the USA?



>>Having said that I checked the EMERs for the AM193 and the specifications state that it was for testing crystals from 3 MHz upwards, not "LF" ones. However it uses a Pierce circuit so I would expect that unless a crystal really is defunct then it should work.

 

In fact it’s a Colpitts oscillator and the EMER mentions that it will function below 3MHz but with decreasing accuracy.

The EMER was re-designated as Test & Measurement J410-419 and was still listed as current in 1982.

 

I went and looked at mine and it’s actually a AM193A (10S/16400).  Almost identical but may be a later variant?  Or possibly cover an extended range.
I have no information covering the 193A but there was an article on it published in the June/July 1992 edition of Radio Bygones.

 

Another useful old bit of kit for testing crystals is the CT432 calibrator unit.  It’s just an oscillator but lots of different crystal bases on it that can be switched in as well as internal crystals.

It also functions as a crystal-controlled heterodyne wavemeter.

 

Andy  G8JAC



Chris_Jones
 

On Wed, Nov 6, 2019 at 05:54 PM, Andy_G8JAC wrote:
Fine by me but ISTR that Hue is in the USA
He is indeed, but sending a couple of crystals shouldn't be too costly unless they fall foul of some export embargo. :(

Chris / G8GFB

vk2ilv
 

Hi all,

There were a few other testers...
75-1100 kcs TS-710 (RFL 537)
1-15 mcs TS-330 (RFL 459)
10-140 mcs TS-683 (RFL 531)

I am reading those numbers off nameplate
from a few photos I have
so I hope they are not in error.

Regards
Ray vk2ilv

On Wed, Nov 6, 2019 at 03:18 PM, Andy_G8JAC wrote:


The old “standardâ€&#65533; for crystal testing was the Test Set AM193 made
by GEC.
As chance would have it the EMERs for the above were added to the Archive
on 30th October. Document Requests are "off" at the moment but normal
service should be restored sometime late tomorrow (8th November)

Chris / G8GFB



Pete_G4GJL
 

Hue, FIG 3 of the ukw1979  attached document is good at c.450kcs. you might want to give it a try on a piece of FR4, else take a look at tFIG48 of the other paper, also attached.
 
Pete
G4GJL

Moderator's Note: attachments are not enabled on this group.

On Wed, Nov 6, 2019 at 7:57 AM Hue Miller <kargo_cult@...> wrote:

I had this bag of those WW2 FT-241 LF crystals, which were used in the WW2 era FM  and ship radios.

I realized I needed to finally make an executive decision on it, so I tested them all. I used the little Chinese

crystal tester I bought off Ebay for $12 or $18. I connected a couple alligator leads to the LF crystal connection

points on the tester.

Result: 74 defective, 13 working = 85% fail rate.

I did find one possibly good frequency, 457 kHz, but – for how much longer ?

Well, this kind of ends any fascination with possible uses of the LF FT-241s for me.

-Hue

 

 

Bob Burns
 

Hi All

I would be happy to test a couple of crystals if they were posted to me.

My Type 193 test set certainly works (oscillates) with crystals down to
200KHz but I have never analysed the impedance network used for
measuring crystal activity to see what it looks like below 3MHz.

The oscillator circuit is a low-C Colpitts which could also be viewed as
a Pierce oscillator and is ideal for crystal testing. I have never (yet)
been able to replicate it in semiconductor technology, even using FET
devices.

--
Regards

Bob

Bob F Burns

C Eng, FIET, MSE. G3OOU, @BobFBurns
Retired Electronics and Software Consultant
http://www.g3oou.co.uk/myexperience.html

Michael O'Beirne
 

Hue
 
Can the FT-241 crystals be opened up and thoroughly cleaned?  That might revive them.
 
73s
Michael
G8MOB
 

From: Hue Miller
Sent: Wednesday, November 6, 2019 3:25 AM
To: armyradios@... ; wireless-set-no19@groups.io
Subject: [wireless-set-no19] FW: FT-241 LF Crystals as a Long - Term Investment Instrument
 

I had this bag of those WW2 FT-241 LF crystals, which were used in the WW2 era FM  and ship radios.

I realized I needed to finally make an executive decision on it, so I tested them all. I used the little Chinese

crystal tester I bought off Ebay for $12 or $18. I connected a couple alligator leads to the LF crystal connection

points on the tester.

Result: 74 defective, 13 working = 85% fail rate.

I did find one possibly good frequency, 457 kHz, but – for how much longer ?

Well, this kind of ends any fascination with possible uses of the LF FT-241s for me.

-Hue

_._,_._,_

jan
 

Hello Michael

FT-241 crystals can be opened with  two screws .
then you will see the small crystal plate that is welded to a wire at each flat side.
the two wires are welded to the connecting pins.
This is a somewhat fragile construction and the the crystal plate could be disconnected from one or both wires after 70 years or so.
The FT-243 crystals are far more rugged and their crystal plates can be cleaned.
Best regards,
Jan PA3FYZ