[time-nuts] Fwd: Re: fluke.l monitor for Thunderbolt . . . the saga continues

Steve steve65 at suddenlink.net
Sat Jul 9 02:21:43 UTC 2011


   Here's where I am with the replacement microcontroller subboard for the
   fluke.l iCruze display.
   I used my bench power supply to slowly bring up the voltage on the
   replacement microcontroller subboard without it being installed on the
   display motherboard. The current limiting was set to about half an amp.
   As the input voltage to the microcontroller subboard got above about
   5VDC, it went into current limiting. This is a board that should take a
   few tens of milliamperes, so something was clearly wrong. And the
   trouble was easy to locate. It didn't take long to find a blob of
   solder on the 3-pin voltage regulator between the output pin and
   ground. I fixed that and the current draw was then about what I
   expected.
   I was reluctant to go further with this board since the solder blob
   surely indicates the board was not tested following assembly. What else
   would be wrong? Was the microcontroller even programmed?
   I forged ahead and installed it on the iCruze board. No joy. VDD on the
   microcontroller was about 3.1VDC. I could see voltage transitions on
   the microcontroller input pin. But nothing on the iCruze. Maybe the
   microcontroller is not programmed, maybe something else is wrong.
   Someone suggested in early June that the original microcontroller
   subboard might be salvageable, could not find the email so I do not
   know who to thank for the advice. I replaced the zero ohm resistors at
   D1, D2 and D2 with 1N914 diodes. The microcontroller VDD went from
   about 5VDC to about 3.2VDC. And it worked. The iCruze is now displaying
   the usual data from the Thunderbolt. It's been running much of the
   afternoon, I hope I'm back in business.
   Wonder if the microcontroller's life has been shortened by having VDD
   at 5VDC for almost a year?
   Thanks all for the insightful advice.
   Steve
   -------- Original Message --------

    Subject: Re: [time-nuts] fluke.l monitor for Thunderbolt . . . the saga
             continues
       Date: Wed, 06 Jul 2011 18:56:45 -0400
       From: Steve [1]<steve65 at suddenlink.net>
   Reply-To: Discussion of precise time and frequency measurement
             [2]<time-nuts at febo.com>
         To: Discussion of precise time and frequency measurement
             [3]<time-nuts at febo.com>

The replacement board looks like the one pictured on Brooke's web site.
Same processor as the older board. Hope to get it installed this evening
or tomorrow, I'll post the results.

Thanks all for the help.

Steve

On 7/6/2011 5:11 PM, Brooke Clarke wrote:
> Hi Steve:
>
> The last couple of board versions have a 3-terminal voltage regulator
> on board.  See the photos at:
> [4]http://www.prc68.com/I/ThunderBolt.shtml#8051PCB
>
> Have Fun,
>
> Brooke Clarke
> [5]http://www.PRC68.com
>
>
> Steve wrote:
>> Hi all,
>>
>> About a month ago I sought advice from list members regarding a
>> dysfunctional fluke.l monitor for my Thunderbolt GPS receiver.
>> Someone suggested that I contact Bob at fluke.l to see what he would
>> do. I took that advice and thought some of you would be interested
>> where I am now. Plus, I need some more advice :-)
>>
>> Communicating with Bob is a challenge due to my not knowing any
>> Chinese and Bob having quite limited English language skills.
>> Following a number of emails back and forth, Bob sent me a
>> replacement microprocessor board.
>>
>> The layout of the replacement unit differs from the layout of the
>> older microprocessor board. The lengths are about the same, but the
>> replacement board is a bit more narrow than the older board. Further,
>> the microprocessor chip on the replacement board is parallel to the
>> short dimension of the board whereas that IC is parallel to the long
>> dimension of the board on the older unit.
>>
>> Does anyone know if the replacement board with its different layout
>> has the voltage problem I was seeing with the older board? The older
>> board has the microprocessor VDD at about 5V. I understand that VDD
>> should be about 3V and am wondering if the replacement board has
>> corrected that problem?
>>
>> Is it as simple as removing the older, existing board and soldering
>> the replacement unit in its place? Any tips as to how to most easily
>> remove the existing board?
>>
>> Thanks.
>>
>> Steve
>>
>
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References

   1. mailto:steve65 at suddenlink.net
   2. mailto:time-nuts at febo.com
   3. mailto:time-nuts at febo.com
   4. http://www.prc68.com/I/ThunderBolt.shtml#8051PCB
   5. http://www.PRC68.com/
   6. mailto:time-nuts at febo.com
   7. https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
   8. http://patriotpost.us/subscription/
   9. mailto:time-nuts at febo.com
  10. https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts


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