HP-71B battery drain with no extra RAM or ROM
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01-05-2016, 06:14 AM
Post: #17
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Q1
I cleaned the circuit board around CR3, C2, R22, VR7, Q1, CR2, C8, C1. Inserted new batteries and the calculator would not power on. The voltage at C8 is +2.3 VDC. When I removed the batteries and used the AC adapter the voltage at C8 is +5.7 VDC and the calculaor functions perfectly. I am going to read through the power supply circuit theory of operation and see if I can identify which component(s) are not operating correctly.
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