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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
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22nd Oct 2014, 9:22 am | #1 |
Nonode
Join Date: Aug 2010
Location: Resolfen, Wales; and Bristol, England
Posts: 2,588
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Plug-in crystal can sizes?
Hi,
I'm trying to find a source for the older style of plug-in crystal can sizes, in other words I'm trying to find out what I need to specify to replace a 5.35MHz plug-in crystal with a 6.25MHz plug-in crystal. Any help would be most appreciated.
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22nd Oct 2014, 9:45 am | #2 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,953
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Re: Plug-in crystal can sizes?
Got any photographs?
The older ones were usually known as "10X" style; then came FT241 and FT243 which were US Government standards. After WWII two new standards emerged - HC6/U and HC18/U (these last two being typically found in radiotelephone gear from the 1950s through to the 1980s). |
22nd Oct 2014, 10:00 am | #3 |
Nonode
Join Date: Aug 2010
Location: Resolfen, Wales; and Bristol, England
Posts: 2,588
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Re: Plug-in crystal can sizes?
Unfortunately I'm 200 miles away from the Heathkit IG-37 that uses them so no photos....
I think the one I need to replace is HC6/U - from the pin spacing specification at http://www.af4k.com/crystal_holders.htm I think that's the one. There's also another in the same footprint that is very much taller and a 19kHz crystal.
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22nd Oct 2014, 10:10 am | #4 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,800
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Re: Plug-in crystal can sizes?
We need a photo to identify the case... with a ruler to show scale because some look the same if you don't have a reference.
We need to know what it's for. Some circuits run the crystal on its series mode, others on its parallel mode. All crystals have both modes but they are different in frequency. Series mode circuits sometimes add a loading capacitor in series with the crystal, so the frequency can be adjusted a little in either direction. This is allowed for in the design of crystals made for those circuits. I have several thousand crystals kicking about the place. 5.35MHz, series mode, 30pF load I know I have, but nothing near 6.25MHz. David
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22nd Oct 2014, 10:10 am | #5 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,800
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Re: Plug-in crystal can sizes?
I must type more quickly....
David
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22nd Oct 2014, 10:23 am | #6 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,800
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Re: Plug-in crystal can sizes?
I've found the heathkit manual.
It's a Pierce oscillator and those use series mode, but it's been simplified quite a lot and it won't oscillate at quite the frequency stamped on the can (some phase shift networks are missing) but for an IF marker, it'll be OK The existing design uses 5.35MHz, so its 2nd harmonic will mark 10.7 MHz... So you want 6.25MHz... for a 12.5MHz IF? I'm trying to think what troughlines use... David
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