[TenTec] Orion II repair

[Howard Smith]

Hi Gary,

The encoders are read using an interrupt, but the keys are read as part 
of the 'main loop'.  I seems that the keyboard scanner has stopped 
scanning because it thinks that a key is still pressed.

The schematic for the keypad board, A8 shows that there are 10K ohm 
pulldown resistors on the row lines.  If one of these resistors happen 
to be intermittent, or have a cold solder joint, the signal would not be 
'pulled down', and the scanning routine would see that row as having a 
key pressed.  Pressing a key causes the row line to be 'high'.  The row 
lines go directly to the big CPLD, which must have several I/O ports 
that are used in the keyboard scanning routine.  This still does not 
explain why the N4PY application seems to fix the problem, or why the 15 
minute wait seems to do the same.

If you look at the Logic board schematic, A7, sheet 11, you will see 
that this board makes the +3.3VDC power for the Main CPU, and the two 
DSP CPUs.  And, there are several aluminum electrolytic capacitors used 
to filter the DC.  I would look at each one of those to see if the top 
has bulged, or it has leaked any electrolyte. This could cause many 
problems if the cap is bad.  On my schematic, the caps to look at are 
C402, 470 uFd/16v and  C417, 100 uFd, 6.3v. While you are in there, also 
check C472, 470 uFd, 16v and C470, 10 uFd, 25v.  These last 2 caps are 
part of the circuit to generate the +10Vdc bias for the electret 
microphones.  This would be similar to the problem of bad caps on the A9 
power board.

The Update application has a Verify function which reads back the flash 
memory and compares it to the file used in the Update Radio function.  
Have you used the Verify function to confirm that the firmware download 
was successful?

Again, I hope this helps find the problem.

73..
Howard, WA9AXQ