Great info guys.
One other idea I sometimes use. With the unit off, measure the resistance
to ground of similar lines, like the row or column scanning lines. If one
is significantly different, maybe something to look at.
Also be aware of any input lines that are above the voltage they are
supposed to be at, like a 3.3V line at 4.0 volts. I ran across this once.
It seems the input lines of the I/O chips are not protected for any voltage
above whatever Vcc is. In my case the line with 4.0 volts worked find but
affected another function (input line) in the I/O chip.
Jeff W4DD
-----Original Message-----
From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Howard
Smith
Sent: Sunday, August 07, 2016 8:47 AM
To: TenTec@contesting.com
Subject: Re: [TenTec] Orion II repair
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
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