[time-nuts] Thunderbolt serial port problem LAST UPDATE

[bill]

On 4/14/2011 8:38 AM, bill wrote:
> On 4/13/2011 5:47 PM, shalimr9 at gmail.com wrote:
>> Fluke.l is using my design except for a number of units which were 
>> shipped with 0 ohm resistors where the 3 diodes were supposed to go. 
>> This powers the CPU with 5 V instead of 3 and most don't last long at 
>> that voltage. However, the symptom is a blank display.
>>
>> Also, I understand some units have an actual 5 V regulator and some 
>> expect a regulated 5 V.
>>
>> I have tested a total of 9 units, 2 from fluke.l one from Dan Karg 
>> and the other are mine against 3 Thunderbolts (2 group buys and one 
>> of the original red boxes) and they all work. As long as the serial 
>> data is enough to bias on and off the 2N2222, it should work.
>>
>> Check the wiring and check that the serial data goes to the CPU. 
>> There is not much that can go wrong if the CPU is working.
>>
>> It is possible that the serial input to the CPU is fried while the 
>> rest of the chip works, but I have never seen that happen. Yet I have 
>> fried a number of these chips (I design HV supplies in my day job).
>>
>> Didier KO4BB
> OK I think I will check the signal going to the CPU. If it is there, 
> then I will throw the unit away.
> If the signal is not at the CPU I will trouble shoot further.
>
> Thanks for the suggestion everybody.
>
> Bill K7NOM
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I just ordered a NEW monitor from fluke..l

Bill K7NOM