HP 71b repair advice - won't power on with batteries or on AC adaptor

[KimH]

(07-13-2021 05:03 AM)teenix Wrote:  Hi,

I've been looking at the 71 for Darren. All boards were cleaned up and look ok. I've added jumper wiring to bypass the zebra connector, and checked it. The power supply rails have battery voltage appearing around the circuit boards. Nothing inside appears to be getting warm with prolonged power applied.

As far as I can see, there is not much else that is user repairable in these machines. The only thing I thought of is a faulty keyboard or a problem with one or more IC's.

I can see a very small current when the battery is connected which disappears when not. This would suggest that it is not fully powering up after the ON button is pressed.

I wonder why they didn't just put a simple pin and socket connector instead of the zebra style. I don't think it would have affected manufacture assembly.

cheers

Tony

Hi Tony,

The fact that it draw a small current is actually (probably) good news. The Static Ram should draw somewhere about 5 uA

my next step would be two fold.

Measure the actual current when the ON is pressed, does it launch the CPU & BUS

If it does, I would take a loupe and check for whether the corrosion has shorted something

Regards
Kim