Author Topic: EEVblog #299 – Retro Phone Camera Teardown  (Read 2026 times)

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Offline tecman

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EEVblog #299 – Retro Phone Camera Teardown
« on: June 26, 2012, 05:24:44 pm »
The answer on the shielding is quite simple.  When the assembly is sandwiched, the (memory) chip sits directly behind the flashtube.  When the flash discharges, a fast rise current, likely in the 10's of amperes flows through the flashtube.  This creates a small EMP (electromagnetic pulse) which can adversely impact any number of chips.  The shield is to prevent this pulse from causing any issues with the adjacent parts.  You can replicate the issue if you have a photoflash (separate, external type) from a camera.  Place the window up to a circuit and pop the flash.  You will see significant induced voltages in the circuit (with a scope attached) and you can easily get a micro based device to hang or reboot when the flash is discharged.

paul
 
 

Online mikeselectricstuff

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Re: EEVblog #299 – Retro Phone Camera Teardown
« Reply #1 on: June 26, 2012, 06:09:36 pm »
As well as the  flash discharge current, the Hv trigger pulse - maybe 1-2kv with fast risetime and minimal loading can capacitively couple to nearby circuitry
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Offline G7PSK

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Re: EEVblog #299 – Retro Phone Camera Teardown
« Reply #2 on: June 26, 2012, 09:00:12 pm »
Also both the trigger pulse and the tube discharge itself produces a broad spectrum of RF as well.
 

Offline PeteInTexas

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Re: EEVblog #299 – Retro Phone Camera Teardown
« Reply #3 on: June 27, 2012, 04:15:09 am »
What was that under the OK5 sticker?
 

Offline codeboy2k

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Re: EEVblog #299 – Retro Phone Camera Teardown
« Reply #4 on: June 27, 2012, 07:10:26 am »
would that be a quartz window over the CCD? or just glass?

 

Offline SeanB

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Re: EEVblog #299 – Retro Phone Camera Teardown
« Reply #5 on: June 27, 2012, 03:33:00 pm »
Plain glass, with an antireflection coating, and probably both a UV and IR filter layer. CCD's are rather sensitive to both.
 


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