[time-nuts] fluke.l monitor for Thunderbolt

David Bobbett d.bobbett at tiscali.co.uk
Sun Jun 5 08:56:40 UTC 2011

The two lines of text are what the iCruze will display when it thinks it 
doesn't have any data. The RS232 input on my system can be unplugged and 
that is exactly what is shown on the display in those circumstances.

Personally, I would start with the simple stuff, just continuity check 
the '232 lines from the iCruze plug all the way back to the PCB.

If that doesn't work, there's a circuit diagram of the device on 
Didier's web site.

73 de David, G4IRQ

On 04/06/2011 22:17, Steve wrote:
> About a year ago I installed one of the iCruze monitors from fluke.l 
> on a Thunderbolt GPS receiver. I paralleled the iCruze with the serial 
> port on my laptop PC. Sometimes the PC was connected, sometimes not. 
> The iCruze worked OK either way.
> Last week I noticed the iCruze was no longer functioning as before. It 
> now alternates between two lines of text: "Trimble LED Monitor" and 
> "Waiting for GPS". Whether the laptop is connected or not does not 
> make a difference. The laptop running tboltmon works ok with or 
> without the iCruze paralleled across the serial data line.
> I substituted another Thunderbolt and saw the same results.
> The iCruze has about 10VDC on its power input.
> I not particularly competent at serial communications or 
> oscilloscopes, but on the DB9 feeding the iCruze I can see the 
> transition of voltage from about -6VDC to about +6VDC. I didn't look 
> at those voltage levels when I installed the iCruze last year so I 
> don't know if that's what it has always been or not.
> I have rebooted the iCruze several times as well as the Thunderbolt 
> and laptop, no change in iCruze behavior.
> Any advice as to where to go from here?
> Thanks.
> Steve

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