Yaesu FT-290R internal battery power?

 I have recently become a licensed radio amateur in the UK. I have acquired a few radios and my main one at the moment is a Yaesu FT-290R. I have been running it off a 12v regulated power supply just fine up to now, but I cannot get the 8 internal "C" cells to power it.
I've put in 8 new Cs, correct polarity.

I've looked at a .PDF of the owner's manual online, no help there.

Any ideas?  I really want to get into SOTA and WOTA, but with no portable PS I can't.... :-(

By the way, my callsign is M6AIM, mike, six, alpha, india, mike.

You could, I suppose, run it in the car ? 

I'll take a wild guess and suggest the switch that switches between external PSU and battery, and which is usually inside the connector for the external supply is damaged - should be an easy fix.

Bottom right of the circuit diagram, around J5

There's a switch to switch between external 13.8V and internal power 8 x c cell = 12V or NIMH 9.6V. if that is switched Ok then probably a diode o/c or battery box o/c's .

Using an analogue meter on low resistance range check all wiring as per the schematic, it's not difficult. Robert Scott VK3URS, I am also an electronics tech of over 40 years. A whole manual can be downloaded but the schematic of the radio is so so. If you require one please let me know at robertscott1949@gmail.com

Re-design7 years ago
Does the meter show the battery to be good when you test the batteries?

Here's a link to the manual if you don't have one.