Tektronix 1240/1241 creating a new GPIB module PCB

[Gregor Samsa]

Hi there,

I own a Tektronix 1241 logic analyzer without the 1200C02 GPIB COMM pack. Unfortunately it seems difficult to get one.
All ICs visible in the picture at the https://w140.com/tekwiki/wiki/1200C02 are still available on ebay and they provide a rom image. So I'm wondering if i could draw up a board in KiCad and have it manufactured.

Can anyone owning one of those machines provide me with detailed pictures of both sides to trace as much as possible of the traces?

I suspect it's a two layer board, can someone confirm this?

[gslick]

Does a giant insect really have need for a logic analyzer?

[Gregor Samsa]

Yes, of course. I can't get out of the room anyways so messing with electronics is a nice way to spend my time. Its a little distraction from that painful apple in my back.

[Jim Narem]

I have added pictures of the top and bottom PCB to the TekWiki entry.  Yes, it's a two layer board.  Good Luck!  Please contribute the design back  to the TekWiki community.

[Gregor Samsa]

Thank you very much!

Yes, I'll contribute that if I get it to work.

[Jim Narem]

That GPIB adapter schematic is in the Tek 1240 service manual, volume 2, board A32, schematic #42.

[gslick]

That GPIB adapter schematic is in the Tek 1240 service manual, volume 2, board A32, schematic #42.

[Gregor Samsa]

I found that in the meantime, thanks a lot anyways.

The schematic is already drafted and the ics are ordered. Haven't finished all footprints and the pcb layout yet.

When everything works I'll draw a case and have it 3d printed.

Edit/Update: The pcb layout is drafted completely, but I'm not done optimizing it. I received the last components in the mail yesterday.

Edit/Update: The pcb is build, I verified the card edge connector dimensions and position. A few minor bodge wires were needed. I'm currently searching my eprom burner, since I misplaced it.

[Gregor Samsa]

I finished my prototype board and it works.

I checked the bell, writing to the screen and querying the software version.

The attached kicad project hast most of the bugs fixed. It will take some time until I get around to finishing this.
Annyway it already is a good starting point if anyone wants to build his own 1200C02 copy.
The LEDs are at a bad position and need to be moved (maybe changed to SMD). The centronix connector needs to be changed to the footprint of the used.

[bcampos@pobox.com]

I'm very interested in the progress of this project, if you have more information I would be grateful!

[Gregor Samsa]

I had the board with the kicad project attached in the previous post (plus some errors i fixed before posting) manufactured, assembled it and flashed the firmware available on Tekwiki (https://w140.com/tekwiki/images/8/86/160-1916-01.bin) into the eprom.
Most of the ICs I used are exactly identical wo the ones in the wikis image. Some similar versions also work (refer the Service Manual Volume II on that).
After installing the PCB the power on selftest has an additional line and the utility menu has the new page visible in the screenshot. By the way: If you hold down any button while booting the keyboard selftest fails on purpose and you can use the testmenu.

When I designed the board there was no pcb mount connector available (at least in Germany) with a reasonable lead time, so i did some large smd pads to directly attach wires. You might want to change that to your liking. Some pictures are attached.
A note on the image: The capacitors on the SMD pads are supposed to be 1206, but i was out of those so i used through hole ones instead.
I had to tilt hte LEDs because they are to near to the boards edge.

I did not have time to create a case for the pcb. It can be tricky to get the pcb correctly into the connector. Maybe the pcb thickness is not correct or maybe a case is needed to hold it straight.

I attached the current state of the pcb, please note that I have not yet had this one produced so I can't verify its working without issues. A lot of components are now SMD, a modern replacement for the obsolete Q345 (Type IRFF122 N-Channel MOSFET) is still missing.


I hope this helps, feel free to ask if you want to know something in more detail!