[time-nuts] Z3805 utility, Was: AW: (no subject)

jimlux jimlux at earthlink.net
Sun May 23 17:47:43 UTC 2010

Bob Camp wrote:
> Hi
> The Symmetricom 3805's have an area on the lower board right behind
> the "control" DB-25. It's very similar to the 3801. There are three
> rows of holes for 0.025" post connectors. One row pair is labeled
> RS-232. The other row pair is labeled RS-422. The original intent
> appears to be to jumper the unit for what ever standard the customer
> desired. 

Such was the case on my 3801.. 10 minutes work with a soldering iron and 
some wirewrap wire, and it was converted from RS-422 to RS-232.

It's not at all clear that the later units are even stuffed
> for the RS-422 option. There are a number of unstuffed IC locations
> on the pc board.
> Your unit sounds like it's either blown, or running RS-422. I have
> never seen one of the earlier HP 3805's so I don't really know how
> much they have in common with the older units. There are indeed USB
> to RS-422 converters out there that will run on a normal PC.

But unless you're running long wires, or happen to have a RS422 
differential system, why bother.  If all you're going to do is hook up 
the PC to check it out, RS232 is much easier to come by.

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