Sharp CE-150 printer/cassette interface questions

[sideburn]

Wow good timing on finding this form.
I just got a PC-1500 and the CE-150 cassette interface and out of the box it gave me a CHECK 6 error. I took it apart and as expected the NIcD batteries were corroded so I pulled them out and soldered up a new set of 5 AA size nicd batteries, confirmed 6 volts, put them in the printer an still a CHECK 6 error. Even with the 9v ac adapter plugged in and charging I get the error. The board looks prestine. The whole set came in the box and looks barely used at all.

I’m not sure what to look for to figure out what the problem is.

Does anyone have any suggestions?