GNT-4601 punch cable help

Mike Loewen mloewen at
Sun Feb 22 21:06:14 CST 2015

    Well, I finally got back to the GNT 4601, and I'm still unable to get 
it to work correctly.  I'm using the following (null) cable, connected to 
the DCE connector (the one on the corner):

DE9		DB25
1		20
2		2
3		3
4		6,8
5		7
6		20
7		5
8		4

    On the GNT 4601, FDX, DC Codes Off.

    On the Linux side:

stty -F /dev/ttyS0 -a

speed 1200 baud; rows 0; columns 0; line = 0;
intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = <undef>; eol2 = <undef>; swtch = <undef>; start = ^Q;
stop = ^S; susp = ^Z; rprnt = ^R; werase = ^W; lnext = ^V; flush = ^O; min = 1; time = 0;
-parenb -parodd cs8 -hupcl -cstopb cread clocal crtscts
-ignbrk brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr icrnl -ixon 
-ixoff -iuclc -ixany imaxbel -iutf8
opost -olcuc -ocrnl onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 
vt0 ff0
isig icanon iexten echo echoe echok -echonl -noflsh -xcase -tostop 
-echoprt echoctl echoke

    With these settings, nothing happens when I send chars to the punch 
(cat > /dev/ttyS0).  If I turn RTS/CTS off (-crtscts), the punch runs and 
chars are punched, although I'm certain not all of them.

    If I try and read a tape from the punch (cat /dev/ttyS0, press the Read 
button on the punch), I get nothing on the Linux side.  The tape reads a 
short burst every time I press Read, but nothing ever shows up on the 

    I'm beginning to the the 4601 has a problem, at least with the reader. 
I've tried to duplicate a tape in Local mode, and nothing seems to be read 
and nothing gets punched.

    Feeling very frustrated.

On Fri, 6 Feb 2015, Simon Claessen wrote:

> well I located the machine and it turns out that the connector closest to the 
> corner is used. we made a nullmodem cable going to a db9 connector and we 
> grab the papertapes on a 600/1200 baud setting as handshaking is somewhat 
> broken on the pc side and we want to be shure to get al the bits. :-)
> Our capture of pdp-8 tapes is here:
> On 02-02-15 16:05, Simon Claessen wrote:
>>  we have a 4601 and i've made a nullmodem cable, but at the moment, I
>>  cant to remember on which connector it went. i think is was the
>>  connector going to the terminal, not the computer one. via the dip
>>  switches on the bottom you can preset three speed settings, available at
>>  a switch on the top. I will take a look wednesday when i'm back at the
>>  museum.
>>  simon
>>  On 02-02-15 05:43, Mike Loewen wrote:
>> >      I have a box of old HP paper tapes to read, and am having an awful
>> >  time trying to build the right serial cable to connect a GNT-4601
>> >  reader/punch to a Linux PC.  Does anyone have a known good cable diagram
>> >  and stty settings that will work?  Thank.
>> > 
>> > 
>> >  Mike Loewen                mloewen at
>> >  Old Technology      
>> > 
> -- 
> Met vriendelijke Groet,
> Simon Claessen

Mike Loewen				mloewen at
Old Technology

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