Floyd,
You say the voltage at U4 pin 5 is -15.4 volts, and that *may* be a
perfectly valid voltage - that is a MARK.
It should not be constantly that way, so check U4 pin 12 - if it is
zero, then the MAX1406 is behaving properly in response. That line
originates from the MCU (Control Board U6) pin 25, and should be +5v
under normal conditions, but pulses to zero when the K2 sends data.
If you find KPA100 U4 pin 12 at 5 volts while pin 5 is going negative,
then replace U4.
OTOH, if U4 pin 12 is at zero volts, suspect the K2 MCU or some problem
on the signal line between those points.
As a quick check on whether the base K2 or KPA100 is pulling that signal
to zero, remove the KPA100 ribbon cable, then power the base K2 and see
whether CB U6 pin 25 goes to +5v with the ribbon cable removed. If it
stays at 0 volts, remove the MCU and make a resistance measurement on U6
pin 25 to make sure it is not shorted - if you read a high resistance,
replace the MCU IC.
The most likely symptom if the KSB2 board has been damaged from plugging
in a serial cable is that you could have damaged either the KSB2 MCU
(AUXBUS line), or Q1 (high voltage on the VRFDET line or the ALC line
can do damage).
Note that if you were previously connecting the USB to serial adapter
directly to the KPA100 AUX I/O connector, it may be possible that no
damage would occur *if* the voltage out of the adapter did not exceed 5
volts and never went negative. In the PC world of short RS-232
signalling, some try to "get away' with those levels, where a real
serial card will typically have voltages in excess of +/-12 volts.
So if you did not previously use the special cable, you will need to
build one - the instructions are in the KPA100 manual page 60.
73,
Don W3FPR
On 8/22/2015 4:28 PM, Floyd Sense wrote:
Anyway, maybe you can help me determine what areas to focus on in the
repair. Here's what I know:
1. The RF chokes RFC6-9 are all intact.
2. The ALC is functioning properly - the power control properly
controls the output
3. U1 in the KPS-100 appears to be functioning as the relays are being
activated at the right time as I switch through the bands.
4. Data sent from Hyperterminal through the USB/serial converter to
the K2 shows up on Pin 6 of the KPA-100 U4 (the Max1706) and can be
seen at pin 26 of the K2 MCU (U6). But, the K2 doesn't act on the
commands that are sent.
5. The voltage on pin 5 of U4 (MAX1406) is -15.4 VDC, seems that
indicates U4 is toast?
I haven't observed any other problems. I found the document written
by Gary Surrency and Tom Hammond regarding this situation. Which
leads me to some questions:
1. Reference is made to possible damage to the KSB2. Do you know
what the symptom would be in that case?
2. Apparently, any damage to the MCU IC might be isolated to just the
input from the interface - pin 26. I say that because everything else
appears to function normally. Are you aware of anything else I might
check for regarding the MCU function?
73, Floyd
On 8/22/2015 3:16 PM, Don Wilhelm wrote:
Anyone who has purchased a used K2 needs to take notice, lest it
happen to you too.
That connector is marked AUX I/O for exactly that reason, it is not a
computer RS-232 connector even though it contains TXD, RXD and signal
ground. As a result, one must always use the special cable that is
built as part of the KPA100 to connect to a computer serial port.
You are not likely to have damaged anything in the KPA100 when
connecting a standard serial cable to the K2, although KPA100 U6 may
have a damaged output at pin 6, and the inductors located just behind
the DE-9 connector should be checked for continuity.
The TXD and RXD signals in the serial cable will connect to U4 just
the same as if the special cable were used.
You could have also damaged the computer serial port because pin 1
was grounded by the K2.
You will find most of the damage will be in the base K2.
Internal signals AUXBUS and VRFDET could have caused the MCU IC to be
damaged as well as the KSB2.
The fact that the 8R voltage rail appears on that connector, that may
have caused further damage.
73,
Don W3FPR
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