Over on his YouTube channel our hacker [CircuitValley] repairs an old TDS8000 scope.

The TDS8000 was manufactured by Tektronix circa 2001 and was also marketed as the CSA8000 Communications Signal Analyzer as well as the TDS8000 Digital Sampling Oscilloscope. Tektronix is no longer manufacturing and selling these scopes but the documentation is still available from their website, including the User Manual (268 page PDF), the Service Manual (198 page PDF), and some basic specs (in HTML).

You can do a lot of things with a TDS8000 scope but particularly its use case was Time-Domain Reflectometry (TDR). A TDR scope is the time-domain equivalent of a Vector Network Analyzer (VNA) which operates in the frequency-domain.

The TDS8000 needs sampling heads attached and it has two large slots on the front for optical sampling heads and four smaller slots for electrical sampling heads. In this video we don’t see any sampling heads actually used, the only thing we see in this video is troubleshooting and repair of the TDS8000 itself. The effective bandwidth of the scope is limited by the capabilities of the sampling heads but according to its datasheet can extend up to 50 GHz, which is seriously large, especially by the standards of 2001!

[CircuitValley] cleans, replaces, upgrades, and fixes a bunch of things during the service of this TDS8000 and documents the process in this YouTube video. In the end he seems to have fixed the problem the scope had in the beginning, where it would hang while loading its main application. We’d love to hear from [CircuitValley] again some time to see a complete system operating with sampling heads attached.

If you’re interested in old scope repair too, then how far back in time did you want to go? Maybe you could start at Recovering An Agilent 2000a/3000a Oscilloscope With Corrupt Firmware NAND Flash and then work your way back to Repairing An Old Heathkit ‘Scope.

If you have very old pieces of analogue test equipment with CRTs on your bench, the chances are they will all have surprisingly similar surrounds to their screens. Back when they were made it was common to record oscilloscope screens with a Polaroid camera, that would have a front fitting for just this purpose.

More recent instruments are computerized so taking a screen shot should be easier, but that’s still not easy if the machine can’t save to a handy disk. Along comes [Tom] with a solution, to hook up a fake printer, and grab the screen from a print.

Old instruments come with a variety of ports, serial, IEE-488, or parallel, but they should usually have the ability to print a screen. Then capturing that is a case of capturing an interpreting the print data, be it ESC/P, PCL5, Postscript, or whatever. The linked page takes us through a variety of techniques, and should be of help to anyone who’s picked up a bargain in the flea market.

This isn’t the only time we’ve touched on the subject of bringing older computerized equipment into the present, we’ve also shown you a disk drive emulator.

Thanks [JohnU] for the tip.

Until recently, hobby-grade digital oscilloscopes were mostly, at most, 8-bit sampling. However, newer devices offer 12-bit conversion. Does it matter? Depends. [Kiss Analog] shows where a 12-bit scope may outperform an 8-bit one.

It may seem obvious, of course. When you store data in 8-bit resolution and zoom in on it, you simply have less resolution. However, seeing the difference on real data is enlightening.

To perform the test, he used three scopes to freeze on a fairly benign wave. Then he cranked up the vertical scale and zoomed in horizontally. The 8-bit scopes reveal a jagged line where the digitizer is off randomly by a bit or so. The 12-bit was able to zoom in on a smooth waveform.

Of course, if you set the scope to zoom in in real time, you don’t have that problem as much, because you divide a smaller range by 256 (the number of slices in 8 bits). However, if you have that once-in-a-blue-moon waveform captured, you might appreciate not having to try to capture it again with different settings.

A scope doesn’t have to be physically large to do a 12-bit sample. Digital sampling for scopes has come a long way.