[R-390] Crystal resurrection

[Chris]

There was a thread about this last November on another group.  One member had an 89% resurrection rate by placing dud HC6 crystals in an oven at 425 degrees for a half hour, and allowing to cool for a half hour before removing.  The solder on the can showed signs of having re-flowed (regular 40/60 melts at 370).  The soldered shut vent was intact, so it would seem the Inside was not further contaminated from the experiment.  

All but one of the crystals came back to life, within reasonable tollerance of their original frequency.  In the time elapsed since, he has not yet reported a repeat failure.  

There being so little volume inside one of those cans, it is reasonable to assume the contact fingers also reached a high enough temperature to re-flow whatever fractured solder might be present.  

Might be worth a shot before physically pulling them apart or donating to the round file in the future.

Regards, 
Chris 

Sent from my outdated iPhone wireless thingy

On Mar 19, 2014, at 12:57 PM, Glenn Little <glennmaillist at bellsouth.net> wrote:

> At what frequency does the repaired crystal oscillate.
> I would suspect is lower than intended because of the additional mass added to the crystal.
> The original crystal was probably sealed in an inert atmosphere.
> 
> I hope that you now have a fully functional crystal.
> 
> 73
> Glenn
> WB4UIV
> 
> 
> 
> At 01:32 PM 3/19/2014, Mark Richards wrote:
>> As I work through some issues with my R-390A crystal oscillator, two crystals were identified as non-functioning: Y402, 10.5MHz and Y413, 9.5MHz.  Considering the cost of replacing these at the only supplier I could find, Fair Radio, I figured that a repair try which saves me $14 each is worth the gamble.
>> 
>> After some digging, I found a fellow traveler:
>> 
>>    http://home.earthlink.net/~chestnutl/Helptipspage3.html
>> 
>> The author found in one instance the internal crystal structure was touching the cover which prevented oscillation and, in another crystal, that re-soldering was needed.
>> 
>> Rather than use a torch, I set my soldering iron to around 800 degrees F and after a minute or so managed to carefully wiggle up the cover.
>> 
>> In both crystals there was no obvious alignment problem, so I set about to renew the soldering.  But, before that, I cleaned each crystal using isopropyl alcohol applied carefully with a cotton ball.  Then, with the soldering iron, touched up each lead, first at the very base where it attaches to the pin, and then carefully moved up to the crystal element, adding a bit of solder.  This was done at around 650 Degrees F.
>> 
>> Tacking the cover back to allow for re-insertion we have success: each crystal came to life!
>> 
>> Perhaps this is non-preservation-quality, but 30 minutes of careful effort just saved me $28 I didn't have to throw.
>> 
>> This R-390A radio is one tough unit!
>> 
>> /K1MGY
>> 
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