Seiko 7A38 - by the numbers

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Forum Home > Parts Info, Tech Tips and Tinkering > Resetting the 7A38-7000 chip

Rob Benham
Member
Posts: 281

On the T series, or at least some of them, there is a sequence to reset the chip.  (it got my tachy function back)   I can find no such reset sequence for the above model.  Are there any tricks of the trade to reboot it?  - It's been powered down several times, though come to think of it, I didn't short the + to - connections as I would to reset some car's  main CPUs.

February 14, 2014 at 12:07 PM Flag Quote & Reply

donwatch
Member
Posts: 568

Rob, good question- Awaiting an answer----I try to keep myself grounded when touching the "board".

February 14, 2014 at 1:18 PM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 14136

You'll both be waiting a long time if you're waiting for an answer from me. All I know is that the 7Axx's C-MOS IC is susceptible to UV. :/


Quote 7A28A Technical Guide (page 11): Be sure to protect C-MOS IC from light with case-back or black paper, etc. while measuring.


See also: http://www2.imec.be/be_en/education/master-thesis/electronics-for-healthcare-and-l/light-sensitivity-of-cmos-ics.html


On the other hand, Si CMOS is innately sensitive to light (from near IR to near UV) causing leakage currents in the transistors that alter the overall circuit performance. It is hence crucial to properly shield the circuits.


PS - but having worked in the industry and 'handled' 100's of components in my time, I'm also well aware of the dangers of ESD. 8)


February 14, 2014 at 1:28 PM Flag Quote & Reply

donwatch
Member
Posts: 568

Paul is this UV sensitivity of the IC a transient phenomena during operation or does the UV exposure cause any lasting damage ? :/
 

February 14, 2014 at 3:34 PM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 14136

No idea, Don.

But I was aware of the sensitivity of C-MOS to UV light years ago (when I worked at intel). So whenever I'm working on a movement I'm always careful to shield the PCB from any direct light - even my work lamps. When (if you ever get the chance to) you buy a genuine NOS Seiko PCB, you'll find it comes wrapped in a black paper sheath. In one of the threads in the Workshop section I posted a photo of a PCB I'd taken outside (in bright sunlight). But that one was already fried.

February 14, 2014 at 3:50 PM Flag Quote & Reply

donwatch
Member
Posts: 568

Seiko is wrapping up the PCB for a reason --in black----

February 14, 2014 at 4:06 PM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 14136

Indeed. 


February 14, 2014 at 4:41 PM Flag Quote & Reply

Rob Benham
Member
Posts: 281

Bag may be black because of an electrically conductive material being used.  However, ever since joining this forum, I've heeded the warning and kept light hitting the chip to a minimum.

.

N.B. since being offered as superb part refund from ameri*pawn for the (engraved) -7000, I'm going to search for another parts breaker to try another circuit.

February 14, 2014 at 5:13 PM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 14136

It's NOT anti-static Rob. It's just (folded) stiff black paper ! I've unwrapped a couple myself. ;)

February 14, 2014 at 5:24 PM Flag Quote & Reply

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