[time-nuts] Opening an Isotemp OCXO

J. L. Trantham jltran at att.net
Fri Oct 28 20:40:39 EDT 2016


Oh never mind.

MAJOR BF!!!

How I 'morphed' S30 into S05 I can't explain.

I suspect it is a 74S30 but I can't prove it.

Sorry.

Joe

-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of J. L. Trantham
Sent: Friday, October 28, 2016 5:57 PM
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] Opening an Isotemp OCXO

Sorry.

74S05D.

Joe

-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of J. L. Trantham
Sent: Friday, October 28, 2016 5:50 PM
To: 'Tom Miller'; 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] Opening an Isotemp OCXO

I have emailed Peter separately earlier today.

The top side marking of the chip appears to indicate it is a TI 74LS05D.

The datasheet is here:

http://www.ti.com/lit/ds/symlink/sn74ls05.pdf

If it is indeed a 'HEX Inverter', perhaps another 'channel' can be wired in place to see if it would work without having to find another chip.

Also, I, too, was wondering if it was 5 V or if there was a 5 V regulator on the board somewhere.

Hope this helps.

Joe



-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Tom Miller
Sent: Friday, October 28, 2016 4:18 PM
To: peter at reilley.com; Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Opening an Isotemp OCXO

Can you see the voltage on the yellow dipped tantalum under the board? I think that is what it is.


----- Original Message ----- 
From: "Peter Reilley" <preilley_454 at comcast.net>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
Sent: Friday, October 28, 2016 3:28 PM
Subject: Re: [time-nuts] Opening an Isotemp OCXO


> That seems the most reasonable thing to do.
>
> Pete
>
>
> On 10/28/2016 3:20 PM, Tom Miller wrote:
>> It looks like that is the only device that could be damaged by 12 volts. 
>> Can you find a replacement and try running at 5 volts?
>>
>>
>> ----- Original Message ----- From: "Peter Reilley" 
>> <preilley_454 at comcast.net>
>> To: "Discussion of precise time and frequency measurement" 
>> <time-nuts at febo.com>
>> Sent: Friday, October 28, 2016 3:10 PM
>> Subject: Re: [time-nuts] Opening an Isotemp OCXO
>>
>>
>>> 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.
>>>
>>> Pete.
>>>
>>> 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
>>>> WB8TSL
>>>>
>>>> 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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>
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