Tetronix AM 503B current probe amplifier - Error LO

[e61_phil]

Hi,

I have a Tektronix AM 503B amplifier on which "LO" flashes after switching it on. The old battery was completly dead. Therefore, I replaced the battery with a new one, but the error is still there.

I measured the voltage on the battery holder and it is 1.5V. It doesn't look like a contact problem. I also double checked the polarity.

Has anyone a hint for me?

Thanks
Philipp