David,
I know you changed the DAC which was the most logical failure point
based on your problem description.
Yes, it is possible that the TONE/XIL signal is now stuck at a low level
instead of high (or vice-versa) which would select a wide filter.
Since resetting the MCU did not help, my next suspect is the MCU itself
or the EEPROM (front panel U3) - unless something is awry with the SCL
signal from the MCU. It is strange that the Power Control works
properly, but the sidetone does not.
If you can locate another K1, you could try swapping the MCU to see if
that is the problem, or you could arbitrarily replace the MCU with a new
one. Without doing some in-depth analysis of the digital signals and
their relative timing with a dual trace 'scope, I can only guess at the
probable causes.
73,
Don W3FPR
On 7/12/2013 3:44 PM, David L DuPuy wrote:
Don, still no sidetone or ability to change XFIL ! I have done the
following:
1) I checked C72 and RP3 solder joints carefully (with a magnifier), and
although they looked fine, I reheated them briefly.
2) I checked the solder joints on U2 two ways: I reheated the joints
carefully. I also checked continuity, e.g., U2 pin 1 to J1 pin 5
connector; U2 pin 7 to top of R13, etc. I also examined the joints with a
glass.
3) I then made a change in STP and also STL, but no sidetone. I then
reset to factory defaults per page 57; no sidetone. I then had to
recalibrate the OPF per page 53, as expected. I also checked VDD on U2 pin
7 and it's 6.14 volts.
4) XFIL is also (still) not changing, so I think the problem is on the
XFIL/TONE line. However, the filter position sounds like the 'wide' FL1
position,whereas it sounded like FL3 when I started to work on it this past
week. I changed the power out again to make sure it's still working fine
after installing U2, and confirmed the power change on the S-meter on the
FT-950, so OUTB is working fine.
The XFIL switch and sidetone worked perfectly from the start, until my
camping trip.
What surprises me most is that the K1 was held in a 'cradle' which was
screwed down to the dinette table in my camper, at an angle of perhaps 70
degrees. So it seems hard to believe the "loose nut" (which may or may not
have caused the problem, and which was lodged behind the leads of RF U5
LM2930T-8) could have gotten into the Front Panel. I checked the voltage
output of the LM2930 early on and it's fine.
The receiver and transmitter appear to be operating normally, using my
FT-950 as a reference. Sorry for such a long email ! and I greatly
appreciate your help. David
tone
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