I was going to use an 8 pack of Double A batteries to power my new MTR 5b. The voltage showed 12.7 volts. Radio seemed to not like this power, then after cycling power switch off and back on again, screen lights but no text shows. Radio beeps and acts OK, but no text. Now what?
If you have the means, you might try removing the two side screws, knurled nuts over phone and key jack and separate bottom cover. Remove the battery for 60 seconds. Put it all back together and set the cw vox back to 300ms our so. If that doesn’t work you may have fried the display? 12 volts max i believe.