You're right, Frank, I did misread P1 pin1 as coming from the AUXBUS. However, the measurements I gave you for U4 Pin 12 is correct. On My board, it swings from 3.5V to 5V with communications under way and a steady 5V with the PC disconnected. Pin swings from 0 to -8V only if communications are underway, otherwise it sits at -10V.
Pins 2, 3, 4, 7, 13 & 15 are all floating (unconnected) and Pin 6 should read whatever is coming from the PC. I noticed that Pin 6 is tied to the high voltage bias on the KIO2, but is left floating on the KPA100. On Sat, 25 Jun 2005 20:27:30 -0400, "Frank Van Cleef W1WCG" <[EMAIL PROTECTED]> wrote: >Hi Matt, > >Thanks for your quick response! > >Looking at the schematic on page 62 of the KPA100 manual, in the lower >left-hand quadrant, I believe pin 12 of U4 is the input side of the TXD >inverter that drives the RS232 interface, and should be 0 or +5v depending >on the state of the RS232 serial signal going from the K2 to the interface. >The AUXBUS lead comes in on the pin of P1 on the opposite side of the >connector from the TX lead and goes to the MCU and pin 6 of J8 (the 9-pin >RS232 connector)through RFC 9, but does not actually connect to U4. I >believe the AUXBUS is OK because the KAT100 works just fine. I have not >looked at U4 pin 12 with a scope to see if it varies at all, but it is >slightly higher in voltage at 0.13v than the others, which suggests that >it's receiving a logic zero from the K2. The output on pin 5 (T2OUT) should >be near one of the RS232 supply voltages of either +12.54 or -5.87 (as >measured at pins 1 and 8) but instead there's only 0.44v. It's also very >strange that the voltages on pins 2, 4, 6 and 7 are all about the same, as >well as pin 3 which is an anomaly -- all these pins should be at one RS232 >level or the other. That's why I'm thinking the chip may be kaput. The >other really bad thing is that connecting the receive side from the computer >(which works fine with other devices such as a chip programmer) drags the >voltage on the receive line almost to zero -- this line is an input to the >MAX chip and the input should be high-impedance and not affect the voltage >on the line at all -- but it does. Gotta keep looking, I guess. > >Thanks again for your response, Matt, and I'll put a note on the reflector >when I do find out what happened. Any suggestions always welcomed!!! > >73, Van W1WCg > > >----- Original Message ----- >From: "Matt Osborn" <[EMAIL PROTECTED]> >To: "Frank Van Cleef W1WCG" <[EMAIL PROTECTED]> >Sent: Saturday, June 25, 2005 5:46 PM >Subject: Re: [Elecraft] RS232 problems with KPA100 > > >The high voltage bias supply on the KIO2 is between -6v to -12, so >your 19.4 is probably sufficient, but the KIO2 Vss, U4 pin 8 is -9v on >my KIO2. The MAX1406 wants from -13.2 to -10.8, but the absolute max >ratings are from +0.3 to -14.0, so you're probably OK with the -5.87. > >The real suspect is that U4 pin 12 should be reading +5V from the >AUXBUS on the control board. The only other use of AUXBUS on the >KPA100 is U1 pin 28 (RB7 Serial Programming Data). > >It would be worth checking out AUXBUX line for a short (C25) or an >open P1 pin 1. > >On Sat, 25 Jun 2005 16:06:46 -0400, "Frank Van Cleef W1WCG" ><[EMAIL PROTECTED]> wrote: > >>Greetings, all you I/O experts out there -- I need some advice, please.... >> >>I'm using K2 #2634 with a KPA100 and KAT100; therefore the RS232 I/O is >>done by the MAX1406 chip on the KPA100. I've done computer control in the >>past but not for some months, so today I was rather surprised when I went >>to try out a new CAT program and could not get it to control or read out >>from the K2/KPA100. A breakout box showed no signal coming from the >>KPA100, and the TXD line from the computer indicated signals until I >>connected the KPA100; then the line seemed to be dragged down almost to 0v >>by the KPA100. >> >>After verifying continuity between the computer end of the RS232 cable and >>the RF chokes on the KPA100 board (RFC6, RFC7) I meaured voltages on the >>MAX1406 chip. Except for the 5 and 12v supply voltages they were not what >>the chart in the manual described. The pin voltages on the MAX1406/U4 chip >>were: >> >> 1 - +12.54 2 - -0.43 3 - -0.03 >> 4 - -0.43 >> 5 - -0.44 6 - 0.44 7 - -0.44 >> 8 - -5.87 >> 9 - 0.00 10 - 0.00 11- 0.10 >> 12 - -0.13 >> 13 - -0.09 14 - 0.00 15- -0.09 >> 16 - 4.96 >> >>The voltage on pin 8 (-5.87) is at the very low end of the expected -5 >>to -25v range shown on the schematic, and even the +30v on the HV bias >>supply is low at 19.54v --almost as though whatever is wrong in the chip is >>dragging >>down the -25v and and the rest of the HV bias. >> >>Resistance on the TXD/RXD leads at the chip is about 100 ohms to ground >>with the power removed. >>All measurements made with a FLUKE 87 DMM. >> >>I don't know how but I'm afraid I've somehow crisped the MAX1406. Is there >>anything else I should try before replacing the chip??? >> >>TIA, all >> >>Van, W1WCG >>_______________________________________________ >>Elecraft mailing list >>Post to: Elecraft@mailman.qth.net >>You must be a subscriber to post to the list. >>Subscriber Info (Addr. Change, sub, unsub etc.): >> http://mailman.qth.net/mailman/listinfo/elecraft >> >>Help: http://mailman.qth.net/subscribers.htm >>Elecraft web page: http://www.elecraft.com > > > _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
