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[time-freq] Reflock 2

Luis Cupido cupido at mail.ua.pt
Wed Feb 29 11:08:10 UTC 2012


Hi Merv,

You must be sure that you don't have any short circuit on the CPLD
pins somewhere, the 180mV may suggest also a short circuit to a pin
being used as output.
(I did not check how I have the unused pins, but they are likely to be 
configured as outputs driving ground, so check a short to a unused pin ).

Once you have discarded this short circuit possibility
the CPLD itself will be the next part to suspect.

Luis Cupido.
ct1dmk.


On 2/29/2012 9:49 AM, Merv Thomas wrote:
> Hi - I have a populated board that is not working. The output of the
> BFT92 transistor on the REF input chain - that is the input to CPLD pin
> 89 GCLK2 is being pulled down to about 180 mv. If I cut the trace on the
> board to this pin then the output from the BF92 goes up to 2.6v Seems
> like an internal short in the CPLD chip.
>
> The input to pin 91 GCLK3 has 2.6v on it from the BF92 in the VCXO input
> chain which seems correct.
>
> Does this show that the CPLD is not serviceable please?
>
> I know most of the forum comments on this subject go back some years so
> I am hoping that maybe Luis Cupido or someone can answer my question!!!
>
> Regards,Merv VK6BMT
>
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