[Kenwood] TS940SAT - troubleshooting questions

[Rob Neece]

You guys helped me fix this radio once before, so I hope you can do it again.

After operating my TS 940SAT a fair amount over the weekend without 
problems, I was surprised to push the power button on Monday and get no 
response -- no lights, no sound.  It wasn't the fuse or the power cord, so 
I started pulling screws.  After a little bit of troubleshooting, I think 
I'm on the trail, but before really taking the radio apart, I need some help.

The main supply on the AVR (X43-1500-00) is putting out 28.5V just fine, 
but there is a smaller supply that provides some lower voltages and it 
seems to be turned off.  Specifically, the base on Q104 is low, cutting off 
the low voltages.  Tracing that  signal off the board to the control unit 
(X53-1420-11), I find that it should be coming from a relay, which is open 
because a signal, TMY, is not low (21 V).  Following that to the switch 
unit (X41-1600-00) I find that I can't trace further, since the board is 
mostly inaccessible without really taking things apart.

Examining the schematic, I found that the CPU on the switch unit is powered 
by a couple of lithium cells.  Hmmmm.  Given the age of this radio, that 
could be the source of the trouble.  Here come the questions:

1) Is a dead radio a symptom of lithium battery failure?

2) My schematic shows the cells in parallel, and they are 3-volt 
cells.  With the power switch off, I measure 3.00 volts on the cell I can 
get to, but the forward drop across D4 is 0.33V (Germanium?), and there is 
2.67 V on VDD.  With the power switch on, VDD rises to 4.4V.  Is this 
correct behavior?  Is there any indication that the batteries might need 
replacing?

3) Assuming the batteries need replacing, I am considering getting CR2032 
replacements and mounting them off the board.  Does anyone have experience 
regarding that?

4) Regarding the service manual, there are some signals highlighted in red 
and some parts are highlighted in red.  Besides meaning they are important, 
what is the significance of that?  I will probably feel stupid when I get 
the answer.

Thanks in advance for your help,
Rob