I just finished building a KXAT1 for my KX-1. When I got to the first
step of testing, I got "---" in the menu. I have reseated the IC, and
resoldered a few joints that looked a little questionable, but no
change in the menu. It looks ok to me, are there any other tests that
I can do to see where the problem is? Thanks.
Well, that is a case where the KX1 microprocessor is not seeing a
response from the KXAT1 microprocessor.
How are you for digital path troubleshooting? Have a digital 'scope?
To troubleshoot in detail is cumbersome.
One thing that you can do is check to be certain the data paths between
the two microprocessors is intact. Be certain that is continuity
between KX1 U1 pin 2 and KXAT1 U1 pin 17.
If your 'scope has a 10X probe on it, you can check at U1 pins 15 and 16
to see if you can detect 4 MHz oscillation. If there is none, then
either the KAT1 firmware chip is defective or the resonator (Z1) is
defective. If you do not have a 10X probe, ignore this test because the
'scope probe can load the circuit and oscillation will cease.
Check the soldering at KXAT1 P3, Z1 and U1, and also at KXAT1 J6 and
U1. Make certain the U1 chip is inserted correctly and there are no
pins bent under the chip (you will have to move the chip up a bit out of
its socket to see any bent under pins).