Hello and asking for help with HP 67 power unit

[GreyUser]

The OP has a 67, not a 20 series Woodstock. There is no risk of ACT damage when operating without a battery. While there is a small risk, it is not the ACT that is at risk. This discussion is well documented in the old forum. It is not relevant to the OP’s situation so I will stick to the problem at hand.

The flashing display, while it could be an ACT failure, it could just as likely be mains ripple caused by a defective 400uf capacitor in the power supply, a common failure in the 82002 charger.

You can test the calculator with a bench power supply, connecting to the calculator’s battery terminals. 4 to 4.5 volts dc at 500 milliamps is required. The battery charger must be disconnected from the calculator when performing this test.