[time-nuts] Opening an Isotemp OCXO

Peter Reilley preilley_454 at comcast.net
Fri Oct 28 15:10:38 EDT 2016

The reason that there was 12 volts on the unit was because I put it 
there.   I should
have tried 5 volts first but the only datasheet that I could find said 
12 volts.
All the eBay units that look the same say 12 volts.


On 10/28/2016 12:53 PM, paul swed wrote:
> I confirmed the pin out matches a 74s30 also. An S30 is TTL. Great pix to
> look at.
> So 12 V on a 5 V chip is indeed a smoker. Find out why there was 12 V.
> OK crazy talk I see a 1K resistor next to the VCC chip. Would anyone be
> crazy enough to use a dropping resistor from 12 V to get 5?? Really bad
> engineering and I don't actually believe they would. But if true a open
> 74s30 would indeed show 12 V on pin 14.
> Good luck.
> Paul
> On Fri, Oct 28, 2016 at 12:48 PM, jimlux <jimlux at earthlink.net> wrote:
>> On 10/28/16 9:13 AM, Scott Stobbe wrote:
>>> The OCXO82-59 datasheet lists 12V supply, 5V clock out, could also be a
>>> blown regulator in your ocxo, if it is indeed a 12v model.
>>> There you go..the design could use a 74S30 as a driver - it's fast,
>> fairly good drive, but runs off 5V.  If the regulator is shorted, and you
>> put 12V on it, it will cook.
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