Part 4
A computer Interface for a Tektronix 576 Curve Tracer
CONTENTS
- General Information about the Tektronix 576 Curve Tracer
- Restoration of a Tektronix 576 Curve Tracer
- Measurements with a Tektronix Curve tracer
A computer Interface for a Tektronix 576 Curve Tracer (You are here)
Owning a 576 myself, I can tell you it is really tedious to do the settings for some specific test. So it usually doesn't do straight away what I have in mind, and the left half of my brain is trying to understand why, and the right half is thinking of not doing something wrong which can damage the tester, or the DUT. And yes, that happened. I am not the only person with that issue, and Tektronix used to sell cards, which fit over the control panel, and you can mark a specific setting there. My late friend Roger Modjeski (from RAM labs, one of the best tube circuit designers I had the pleasure to know) owned a 576, and he said to me he didn't like it, because it was too difficult to use. Actually he was working on something digital by the same principle, but easier to use. Well, one project is always your last, and Roger choose for this an OTL design, based on Julius Futterman's earlier ideas. So the digital 576 never made it. Today, I rather just picture the 576 settings. And here, a computer interface, storing the settings, and reading them from computer memory, via the relay input connector, would be a great help.
A 100% automatic computer interface is almost impossible to retro build for the 576. However, many of the internal settings like mV per Division, and many others, are done with miniature relays. The system with overlay sheets, was just for occaisional use. For professionals, Tektronix had a card reader Type 172, which could be inserted where is the test receptacle, so you could make your own test cards with a punch tool, and do the control settings faster. These are easy to find on Ebay, but I never had one myself here. It's not a real card reader with micro contacts, but you need to plug in the pins. They remind me of the programming of the Russian "Kalibr" brand L3-3 tester.
There is a USA company who builds an interface device for this purpose indeed. So simulating this card reader in software. From what I can see, they are using object-oriented programming, which is really easy, because the only thing to do is, read or apply on/off voltages at the relay interface connector, which is already there. With such software, you can place modules from the menu on the user interface screen. Then, the modules need to be told where to write data to and read from. Some remaining settings you need to do yourself, like select the high voltage, and a few more. The relay settings are done via PC screen, or from stored settings. Then, replicating the live screen is not difficult, because the horizontal and vertical amplifiers are running at 100 (or 120) Hz only, and this is a small challenge today for any A/D converter. Moreover, the horizontal and vertical deflection signals can be easily tapped on a low voltage level, and you have everything you need. Once you have the live screen, you can make screen shots from it. All in all, this interface is not difficult to make, but as with all such projects, it's a time trap. So you are better off just buying it when it exist.
The advantage is the easier saving and faster restoring of settings, and digital screen, which can also be saved. Only it adds little to the precision or the possibilities. Their price on this moment, I have seen 4500 US$ on Ebay. Which is really fair, because that includes a serviced and calibrated Tek 576, with one year guarantee in it. So not a flaky one from somebodies uncle, which costs you still 1400$ and when you service it, you'll find why it was sold. Besides they have the trouble of shipping such a crazy weight item safely, also in case of guarantee. I would say the price is really a very good buy.
Here is their website and they also have some youtube videos.