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HP-97 Display flickering


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Post: #2
08-28-2013, 04:59 AM
davorin Offline
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Good morning from Switzerland ;-)

Just received a HP-97 this morning and after some resoldering it seems to work.

One question though:

Is the noticeable display flickering normal?
Especially the flickering is heavier in the left hand digits.

Or something to do we have here 50Hz instead of 60Hz?

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Post: #3
08-28-2013, 05:14 AM
Marcus von Cube, Germany Offline
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Do you have a good battery? The battery is required to regulate the supply voltage.

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Post: #4
08-28-2013, 05:47 AM
davorin Offline
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Pretty dead battery pack ;-)

But thanks for pointing me in the right direction...

Added a small 100uF capacitor across the 5V power supply, close to the AC input where it says "+" and "-" on the PCB...now the flickering has gone and also the printer motor moves...though one gear is worn out...

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Post: #5
08-28-2013, 07:47 AM
davorin Offline
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Well....voltage is a little too high now with the capacitor....

Gonna use a standard 5V USB power adapter now to be on the safe side ;-)

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Post: #6
08-28-2013, 11:01 AM
Marcus von Cube, Germany Offline
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Replacement battery packs are available online on a well known auction site.

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