Tektronix TWD120 100MHz dual channel digitizer teardown - opinions? - Page 1
Forum section: electronics / general

author: GnatGoSplat
author_rank: Regular Contributor
timestamp: July 31, 2012, 07:08:40 pm
content: This is a Tektronix TWD120 100MHz dual channel digitizer. It's a PC-based oscilloscope from around 1994 with a SCSI-2 interface. The software is 16-bit originally for Windows 3.1, but it'll run in any 32-bit Windows. Only problem is it seems to crash when the window is resized beyond SXGA resolution (1280x1024).MC68331 16MHz 32-bit Freescale MCU4x M5M51008 (1Mbx8) 4MB SRAMDS1630AB 32KB NVRAM2x AM28F020 (256Kbx8) 512KB Flash ROMNCR 53C90A SCSI ControllerMC68230 Parallel Interface/TimerMC68681 Dual UART8x IDT7164S20Y (8Kbx8) 64KB SRAM buffer for ADC?My question: Is this good enough for a beginner to learn? Or is it too outdated? This is what I was told by another TWD120 owner.QuoteI don't know enough about scopes to know if that makes it good enough to keep, or if I should invest in a lower-end Rigol.I bought this a long time ago and have mainly just used its AUTOSET function in the software to view waveforms, but I'd like to learn more advanced scope usage.

author: FenderBender
author_rank: Super Contributor
timestamp: July 31, 2012, 09:37:05 pm
content: Depends on the software? Is it unbearable? Okay? Good?

author: GnatGoSplat
author_rank: Regular Contributor
timestamp: August 01, 2012, 01:38:07 pm
content: The software seems okay, I always get the urge to maximize it which crashes it, but if I can resist the urge, it works fine. However, so far I've mainly just used the AUTOSET button and changed volts and time scales. I'm mainly just curious if the hardware sounds adequate, mainly from the part I quoted. For example, he mentions a 5ns sweep time. Is that adequate by today's standards? Also, the official spec is 100MS/s. Is that the sample rate in Mega-Samples per second? If so, then a Rigol 1052E has a 10x faster sample rate. That makes 100MS/s sound really slow, but is it adequate in real life?

author: free_electron
author_rank: Super Contributor
timestamp: August 01, 2012, 01:49:49 pm
content: Some of the guts look like they have been recycled from tds5xx series scopes.

author: T4P
author_rank: Super Contributor
timestamp: August 01, 2012, 02:02:50 pm
content: Quote from: GnatGoSplat on August 01, 2012, 01:38:07 pmNot 100x ... 10xanyway you are good for at most 20MHz ( yeah ... x5 is not any good )USB scopes i have seen are mostly 200Megsamples anyway

author: GnatGoSplat
author_rank: Regular Contributor
timestamp: August 01, 2012, 02:13:28 pm
content: Quote from: T4P on August 01, 2012, 02:02:50 pmD'oh! Math fail, fixed it.Are you basing that 20MHz on the 100MS/s or 5ns sweep?

author: Fraser
author_rank: Super Contributor
timestamp: August 01, 2012, 02:29:40 pm
content: That unit looks typical Tektronix high quality kitI would love to own it myself. People appear to get very hung up on maximum sample rates and bandwidths when it is not always an issue. I am an RF Tech so prefer analogue oscilloscopes anyway, but I own several DSO's and Analogue/Digital CRO's. Each has its weak and strong points. The real time single sweep capability of your unit is around 5 to 10MHz with a 100 MS/s sample rate. That is not terrible, its just a little slow for todays faster clocking digital equipments. For general hobby electronics it is probably a good storage scope for lower frequencies. You could buy a half decent used analogue 100MHz Cathode Ray Oscilloscope to partner it and provide the higher frequency capability if needed. I personally find DSO's like my Rigol great for digital work but not so great for my RF work. I have used lower sampling rate DSO's for IF frequency work at 455kHz and also for battery discharge monitoring. They can also make great transient recorders. Attach a thermocouple adapter and you have a temperature graphing capability as well. Slow sampling rate DSO's are not without their usesDecide what sort of frequencies you want to look at, and whether storage is essential. Then you will know if you need to upgrade. I would suggest if an upgrade is the way forward, sell your Tektronix on ebay and you will likely be pleasantly surprised at the return you get on it. Then go buy the DSO or analogue scope of your choice.

author: GnatGoSplat
author_rank: Regular Contributor
timestamp: August 01, 2012, 03:25:58 pm
content: Thanks, I'll keep that in mind. Though I probably have a lot to learn before I can even recognize whether I'm coming up on its limitations.

author: T4P
author_rank: Super Contributor
timestamp: August 01, 2012, 04:31:21 pm
content: Quote from: GnatGoSplat on August 01, 2012, 02:13:28 pm100Megsamples ... single sweep at best 5-10MHz20MHz is the maximum you can go before your waveform goes completely, maybe.Due to Nyquist–Shannon sampling theorem it's at best 10-20MHz

author: nctnico
author_rank: Super Contributor
timestamp: August 01, 2012, 07:16:53 pm
content: Actually you'll get aliasing artifacts. If you feed 101 MHz into a 100Ms/s scope you'll see a 1MHz sine wave. Usually this isn't a real problem though. IMHO its a decent piece of hardware. If you add an old Pentium 2 laptop and use a compact flash card as a hard drive you'll have a neat portable kit.

author: joat
author_rank: Newbie
timestamp: March 16, 2013, 08:23:44 pm
content: I was wondering if anyone has a pdf manual for the twd120 they would be willing to share. I cannot find one anywhere. Thank you.

author: rsjsouza
author_rank: Super Contributor
timestamp: July 15, 2019, 01:32:52 pm
content: Please apologize for resurrecting such old post, but perhaps others that were involved at the time will be notified by it.About a month ago I received a unit in pristine condition with all manuals and software and was trying to make it work here. After lots of mucking around with some ancient systems I have here, I was finally able to put together an ancient Athlon 64 3500 with 1GB RAM, Adaptec AHA2940U and running Windows XP.I followed the excellent instructions shown at the link below but with a minor caveat on XP: when installingAdaptec's WINASPI driver, you must also install the Windows 98 version to properly add the 16-bit version of this driver. Runninginstall.bat X86will do.http://www.chichak.ca/file/Tek_TWD120.htmlThe Adaptec drivers above have a utility called aspichk.exe that works very well in detecting which versions are installed. In order for the unit to work all drivers must be installed.On this configuration I didn't need to muck around with the shim driver mentioned in the reference above - it worked fine given the SCSI adapter on Windows XP was already on bus 0.The unit with its User's manual (to be scanned when time permits):With a FY6600:Its software. It is pretty well done and the only perceived crash was trying to resize to full screen (SXGA 1280x1024).Anyways, I hope this information helps recover many of these interesting units in the field.

author: rsjsouza
author_rank: Super Contributor
timestamp: August 07, 2019, 08:25:28 pm
content: I finished scanning and uploading the TWD 120 Digitizer Instruction Manual 070-8821-00 to ko4bb at:http://www.ko4bb.com/getsimple/index.php?id=manuals&dir=Tektronix/Tektronix_Miscelaneous