[time-nuts] Lightning 1, tbolt 0.

paul swed paulswedb at gmail.com
Thu May 12 01:57:07 UTC 2016


Yes the last word is accurate for lightning and TBolts or anything else.
The super hot chips a clue to trouble. The other thing on a hit is that
months later stuff starts acting up.
Seven hits over 30 years and yes I ground stuff.
Regards
Paul
WB8TSL

On Wed, May 11, 2016 at 8:48 PM, Scott Newell <newell+timenuts at n5tnl.com>
wrote:

> At 03:19 PM 3/31/2016, Ryan Stasel wrote:
>
> I do know 74AC04’s are horribly prone to ESD damage… replaced more than a
>> few when working on older bench multimeters.
>>
>> You may need to get in there and probe a bit. In my case, my bad RS232
>> driver was drawing about 350mA and getting VERY hot, VERY fast.
>>
>> Good luck, and let us know!
>>
>
> Finally replaced the RS232 interface chip and the 'AC04 PPS buffer. Still
> dead.
>
> Probing around, it looks like the UART output is stuck in a break
> condition (232 out is at +9V, and the input to the driver is near ground).
> The 32kHz CPU rock, the 3.684 MHz clock, and the 10 MHz OCXO are all
> singing. No PPS visible anywhere on the 'AC04. I do see bus activity on the
> SRAM. The CPU is getting very hot--it's the hottest chip on the board,
> nearly as hot as the OCXO. There is a ~60 kHz clock visible on the temp
> sensor. I couldn't find anything that looked like the GPS bitstream--maybe
> the CPU has to program the synth first?
>
> I guess I can strip the OCXO off the board--it's a good Trimble 37265 from
> the TAPR group buy.
>
> Crap.
>
>
> --
> newell  N5TNL
>
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