[time-nuts] Lightning 1, tbolt 0.

Ryan Stasel rstasel at uoregon.edu
Thu Mar 31 16:19:36 EDT 2016


Hi Scott, 

The RS232 “driver” is a MAX232 clone (mine was an Intersil 232IBE). I have since replaced with a MAX202 from TI, as it is a direct drop in replacement, and has much better ESD/Latch-up protection. The MAX3232 has similar protection… the Maxim and TI MAX232 parts both seem to occasionally suffer from latchup problems according to some threads online, and most responses from TI, at least, point toward the MAX202 or 3232 as better alternatives. Just make sure to order the SOIC16-W package… I made the mistake ordering the narrow at first. Nothing some 30awg wire couldn’t fix, though. =P

The PPS “buffer”, I think, is a 74AC04M, but don’t quote me on that. I’m going off memory, and these two pages: http://www.leapsecond.com/pages/tbolt/photos.htm and http://www.prc68.com/I/ThunderBolt.shtml

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! 

-Ryan Stasel

> On Mar 30, 2016, at 19:06 , Scott Newell <newell+timenuts at n5tnl.com> wrote:
> 
> 10 MHz output active, no PPS, no comm with LH.
> 
> My tbolt was disconnected from the outdoor GPS antenna today, and so I wasn't too concerned when we had a strike in the backyard this morning. The PC attached to the serial port and PPS output died, and that cable was fairly long, so I guess that's what did it in.
> 
> Anyone know off hand what part it uses for the serial driver and the PPS output buffer? Or is it likely a total loss?
> 
> -- 
> newell N5TNL
> 
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