[Elecraft] K2 - KPA100 RS232 interface repair

Sat Aug 22 18:38:51 EDT 2015

OK - many thanks, Don.  I'll get busy looking at those things.

73, Floyd

On 8/22/2015 6:33 PM, Don Wilhelm-4 [via Elecraft] wrote:
> 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
> >>
> >
> >
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email] 
> </user/SendEmail.jtp?type=node&node=7606582&i=0>
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email] 
> </user/SendEmail.jtp?type=node&node=7606582&i=1>
>
>
> ------------------------------------------------------------------------
> If you reply to this email, your message will be added to the 
> discussion below:
> http://elecraft.365791.n2.nabble.com/K2-KPA100-RS232-interface-repair-tp7606571p7606582.html 
>
> To unsubscribe from K2 - KPA100 RS232 interface repair, click here 
> <http://elecraft.365791.n2.nabble.com/template/NamlServlet.jtp?macro=unsubscribe_by_code&node=7606571&code=ZmxveWRAazhhYy5uZXR8NzYwNjU3MXwxMDMyNDYzNzk0>.
> NAML 
> <http://elecraft.365791.n2.nabble.com/template/NamlServlet.jtp?macro=macro_viewer&id=instant_html%21nabble%3Aemail.naml&base=nabble.naml.namespaces.BasicNamespace-nabble.view.web.template.NabbleNamespace-nabble.view.web.template.NodeNamespace&breadcrumbs=notify_subscribers%21nabble%3Aemail.naml-instant_emails%21nabble%3Aemail.naml-send_instant_email%21nabble%3Aemail.naml> 
>

--
View this message in context: http://elecraft.365791.n2.nabble.com/K2-KPA100-RS232-interface-repair-tp7606571p7606583.html
Sent from the Elecraft mailing list archive at Nabble.com.