Tektronix Logic Analyzer

A logic analyzer is a device somewhat like an oscilloscope, in that it displays the waveforms of electronic signals on its screen. It differs from a traditional scope in that it captures data in memory for longer study of ephemeral events rather than only displaying what’s happening in realtime (modern capture scopes do this, too); it typically has many channels (8, 16, or more plus clock and other “meta” inputs) rather than one, two, or four; and it can be configured for complex trigger events rather than only the level of a particular signal. In short, a logic analyzer does for digital system troubleshooting what a scope does for analog signal work.

I’ve never had a logic analyzer, and last spring when I started working more with the LogoChip and other digital parts, I started hankering for one. I found and bought this Tektronix on eBay for only $30 plus shipping:

Tektronix Logic Analyzer, Front

It has text-based menus, online help, and a charming monochrome green screen. It’s built almost like general-purpose 6502 luggable microcomputer, with a big stack of signal handling boards in it.

Tektronix Logic Analyzer, Interior

The only catch was, it didn’t come with any probes. I was hoping at first that all I needed was ribbon cables to fan out from the dual-row headers on the front panel, but I couldn’t find pinouts anywhere (including online). I emailed Tek’s tech support asking whether they might still have pinouts available that I could download (since they no longer sell or support this analyzer and wouldn’t be losing any money on me), and I got an incredibly helpful phone call back from them.

Their tech support representative indicated that the probes have active CMOS circuitry in them, so you need more than just pinouts; and he gave me the model numbers of three different probes that should work with that analyzer. I saved an eBay searched and waited, until a couple of weeks ago when one of them popped up and I bought it for about $25.

Tektronix P6444 Logic Analyzer Probe

There’s obviously a fair bit of circuitry in there that I wouldn’t expect to be able to duplicate, so I’m glad to have bought it. Now I still need cables to go from the probe module to the circuit being analyzed. And after I received the probe module, the seller emailed me to say that in the same box as the module, he also had these connectors that went with it; did I want them for another $25?

Tektronix Probe Wiring Assembly

Okay, if he’d included them in the auction with the module they go to, he probably wouldn’t have got any higher bids. It’s his job to maximize his profit, so I suppose he’s doing what he ought to. But I feel like a guy who just negotiated to buy an antique auto out of a farmer’s field, only to be asked whether I’d also like to buy the engine that goes with it that I have over here in the barn. Yes, sure I’d like the wires that go with the probe module you already sold me; and at the same time, no, I really don’t feel like sending you any more money for something that really belongs with what I bought the first time.

Furthermore, most of the time I’ll be using the analyzer, it’ll be with circuits on a breadboard, where I’m going to have to make my own cables terminating in pins anyway. These probe tips have really cute grippers on them that are perfect for grabbing onto classic DIP leads, but useless on a breadboard.

But I was still wavering, since I don’t know how to describe these tips well enough to save an eBay search that would pick them up, making this a rare opportunity to get something I might eventually want.

I called Cort last night to ask his opinion, and the moment he said “troubleshooting your arcade games,” I knew what the answer was.

I just sent the PayPal.

13 Responses to “Tektronix Logic Analyzer”

  1. Nick says:

    Do you have the model numbers of the other probes that would work. I am buying a 1230 which is the exact same as the 1220 except more inputs.

    Thanks Nick

  2. Keith Neufeld says:

    The model numbers I got from Tek were P6442, P6443, and P6444. Hope that helps!

  3. Dan Roganti says:

    Hello,

    I have a Tek 1240 LA too with 3x P6444 logic pods and 1x PM403 6502 disassembly pod. I was hoping you might have some info on where to find more accessories other than eBay. I was hoping to find more of the 10pin idc ribbon cables for the probe wires – I had to make some myself for the moment. Also I was hoping to find disassembly pods for the various processors, 8080, Z80, etc.

    thanks !
    =Dan

  4. Keith Neufeld says:

    Dan, I have no idea where to find more Tek probes. I didn’t even know the 6502 disassembly pod even existed in the real world — I’d be very interested in knowing more about that. If you have pics of the interior, I’d really like to see them — maybe it’s something that could be cloned, or even reverse-engineered to figure out how to make a ROM for other disassembly. (Maybe.)

    As to the ribbon cables — I think making your own is about the only alternative you’re going to find to eBay.

  5. Brad says:

    I’ve got a 1220 also; also no manual. I did find one with another LA once, but the seller wouldn’t sell it separately, nor would he scan it… not suprisingly, but hope springs eternal.

    I have a PM 403 (6502/65C02/65C802 module) and a PM 404, 8085 module, along with a 6442 general purpose module.

    Have you ever found a manual for yours? They’re easy enough to use… but we always want to know all the details, right?

  6. Andrea says:

    Dear All,
    I got a 1225 running, without probes, I didn’t find any manual/article/specs or other stuff which could give me the right probe model compatible with 1225. In some sites it is written P6442, is it the only one or also P6444 could be successfully used?
    Please help me, thank you in advance, regards, Andrea

  7. Keith Neufeld says:

    Andrea, I have the impression that the P6442, P6443, and P6444 all work with the 1220, 1225, and 1230, but I don’t actually know for sure.

  8. Dan Roganti says:

    Sorry for the late reply, I lost track of your website
    I’m not sure if you found this yet.
    There’s a website which has a pdf file of the 1230 brochure.
    I made a typo in my last post, I actually have the 1230 LA.
    This shows all the available accessories and pods for this model.
    I downloaded it before the site disappears.
    http://www.tucker.com/webimages/productpdf/00001837.pdf
    I’ll have to take a break one day and open it up to take some pics.
    It would be great if we could reverse engineer this for other processors.
    Then you wouldn’t need to buy more processor pods.
    You could then make some sort of adapter instead for the different cpu pinouts.

  9. Dan Roganti says:

    Hi Keith,

    Just a thought, I’m thinking about reproducing the Processor pod for the 602. And perhaps if I dig around some more, I hope to find the info on how to program this to clone a 8080 and Z80 processor pod.

    There’s an EPROM in the processor pos which is loaded into the 1230 series analyzers to configure the settings, trigger memory or I/O operations and also map the 6502 instruction set so you can trigger on the target’s firmware.

    I have to find a manual for the 1230 to see what processor they use, maybe it just another one of the 8bitters. Then it should make programming easier. Sometime later, I can upload the Eprom in the processor pod, so we could all try to disassemble it.

  10. Dan Roganti says:

    oh and about the processor pod itself. I forgot to mention, it’s very easy to reproduce this, nothing but good ol’ TTL logic in there. It’s not like the Logic pods we have, as pictured here on your website.

  11. Dan Roganti says:

    oops, I skipped right over the picture you have of the guts. You mention it looks like a portable 6502 computer. Is that all that’s in here ? That should be a breeze. Now we would have to figure out the Software I/O for how it manages to configure the settings inside the Logic Analyzer. I’m not sure if the manual will tell use this – if I find one.

  12. Wayne Pavy says:

    Could you please photograph the different circuit boards and list the position of them.I dismantled mine and the bottom two boards look similar but the jumper positions are different and I forgot which is the bottom board.I would certainly appreciate it if you could put the photographs on your web site.Regards Wayne

  13. Wayne Pavy says:

    Keith Thank you for your webbsite it is informative,please do not bother of photographing your boards as I expanded your internal photograph which shows two boards so it is easy enough to know where the last board goes even though I have a 1220 the bottom two boards are different than yours.Regards Wayne

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