Refurbishing a Tektronix TDS7104 Oscilloscope

Introduction The TDS7104 Common Failures Make an Image of the Hard Drive CR2032 Backup Battery Replacement and Display Brightness Do NOT Remove the Front Panel Scope Disassembly A Failed Attempt at Switching over to an SSD Reinstalling from Scratch: Windows 2000 Pro or Windows XP? Not All TEAC CD-224E Drives are the Same Installing Windows 2000 Pro on an Old Machine through a Virtual Machine Burning the Windows 2000 Pro Installation Disk onto a USB Stick Booting from USB Stick with a Plop Boot Manager Installing Windows 2000 Pro Installing Special TDS7104 Drivers Installing Tektronix Firmware Installing TekFonts The Scope is Working! Re-enabling the Existing License Cleaning Up The End References Footnotes Introduction A little over a month ago, I ran into a Tektronix TDS7104 at the Silicon Valley Flea Market, where else? Other than some dirty buttons, a few smudges here and there, and the usual assortment of calibration and asset tracking tags, the unit was in excellent cosmetic shape, but the price tag of $700 was way out of line: as I write this a try-before-you-buy TDS7104 can be had on Craigslist for the same price. But Paul, the seller/liquidator, has a habit of saying “I’ll make you a deal” and he did before I even asked: $300. That’s still a lot by flea market standards, but a pretty good price for a TDS7104… if you can get it to work. At home, the scope powered up right away and it booted straight into the main scope application. Other than a screen that was way too dim, everything seemed fine. But when I tried it again a few hours later, it got stuck at the BIOS screen with a CMOS battery error. In this blog post, I go over the steps I took to get the scope back in top shape. The TDS7104 The TDS7104 is a 4-channel oscilloscope with 1 GHz bandwidth and a maximum sample rate of 10Gs/s, though that’s only possible when using 1 channel. The sample rates drop to 5 Gs/s for 2 channels and 2.5 Gs/s for 3 or 4. Even by today’s standards, the specs exceed those of hobbyist class oscilloscopes, think Rigol and Siglent, though there’s a price to pay in terms of weight, 39 pounds, and volume: they’re as wide and deep as the earlier TDS700 series, for example, and much taller. The TDS7054 is its little brother, figuratively speaking only. In the same chassis, it has a 500 MHz bandwidth and 5 Gs/s. Unlike more advanced TDS7xxx models, the 7104 and 7054 have BNC connectors instead of custom Tektronix ones that require probes or adapters with prices that exceed today’s price of the scope itself. Introduced mid 2000, these scopes initially ran Windows 98 but they must have upgraded soon after to Windows 2000 Pro Embedded, because that’s what mine has and it has components with a late 2000 timestamp. The PC motherboard has the little-used NLX form factor. Mine was a RadiSys SF810 with a Socket 370 and a 100 MHz front-side bus. Originally, these scopes shipped with a dog slow 550 MHz Celeron, I got lucky with a 850 MHz Celeron. The fastest compatible Celerons with 100 MHz FSB go up to 1.4 GHz, but they’re pricy. You should be able to find 1.1 GHz versions for around $20 on eBay. Unlike my Agilent 54831, the 640x480 LCD screen has resistive touch control which makes it possible to use the advanced scope features without the need to connect a mouse. In addition to the PC motherboard, there is a PowerPC-based controller board that runs VxWorks like many other Tektronix products of that time, and a large acquisition board. In addition to a few hardware options such as a 4M/channel sample memory, up from a 500k default, there are plenty of software options for advanced measurements: jitter testing, USB certification testing, etc. Both the software and hardware options can be enabled with a license key. To the suprise of no one, that protection scheme was hacked long time ago… According to the labels on the chassis, my scope came from the PSD lab at Cypress Semiconductor, where it was used for things like measuring high-bandwidth signals such as the battery current on the Apple TV Remote. :o) Common Failures As always, you’ll find a bunch of hobbyists trying to revive this kind of scope on the EEVblog forum, Youtube and some blogs. Here are the most common failures: PC motherboard CMOS backup battery dead PowerPC backup battery dead Hard drive dead Power supply capacitors leaking I was lucky and only had to deal with issues 1 and 3, sort of. A dead PowerPC backup battery will give you considerably more work than what’s described in this blog post. After booting up the TekScope application will show the splash screen, but it will hang there forever. You will need to: Take apart the scope even more and take out all the PC components: floppy, HD, CDROM drive, motherboard. Replace the top cap of the Dallas DS9034 NVRAM with a new battery. Connect with RS-232 to the PowerPC controller board. Enter a bunch of values to store in the NVRAM. You can detailed step-by-step instructions here. You should also check out this repair video by Feedbackloop. A dead power supply is another common problem. It often will prevent the scope from booting up at all. There are plenty of discussions about this on the Eevblog forum, here is one that has the reverse engineered power supply schematic attached. Often, all that’s needed is to replace some leaking capacitors. I didn’t have to do any of that… Make an Image of the Hard Drive Whether the machine boots or not, your first step should always be to make an image of the hard drive, a 6 GB IBM Travelstar in my case. Like my Agilent 54831, I thought that I’d have to open the case to access the drive, but you can just push on the spring-loaded black cover in the back and pull the drive sled out1. Nice! Remove the drive from the sled, plug it into a USB-to-IDE adapter, and extract the data. On Windows, I use HDD Raw Copy Tool. I often use Linux for this kind of maintenance, but since this scope is a Windows 2000 machine, I ended up needing a bunch of Windows-only tools. The Travelstar HD was running on fumes, because HDD Raw Copy Tool ran into a number of corrupt sectors during the copying operation. I was lucky, the impacted files were related to the French Windows 2000 manual, but it shows the importance of making an image of the drive ASAP. CR2032 Backup Battery Replacement and Display Brightness You’ll need to open up the case to get to the PC motherboard CR2032 backup battery. See the next 2 sections for that. After installing the new CR2032, the scope booted back up again, but the TekScope window had some weird corruption and waveforms didn’t render right. This was because the Chips & Technologies 69000 graphics card settings had been changed to a 256 color palette mode. It needs to be set to True Color 24-bit mode.2 Notice the presence of 2 video cards: an Intel 810 integrated graphics card and the Chips & Technologies 69000. The latter is responsible for driving the LCD screen. It has special hardware to render oscilloscope waveforms in overlay mode: they are sent by the acquisition board to the video memory through DMA3 without CPU intervention. While we’re on the topic of the display: after installing the CR2032, the LCD display was still very dim, to the point that I was researching replacement CCFL backlight tubes. That turned out to be entirely unnecessary: the TDS7104 doesn’t have a way to control the intensity of the LCD backlight. The previous users must have used it in a dark lab and dialed down the brightness by adjusting the gamma settings in Windows: Do NOT Remove the Front Panel I’m putting this section before the Disassembly one to make sure those with a low attention span get the message: chances are high that you don’t need to remove the front panel. And that’s good because, unlike the TDSnnn series scopes, the front panel has some plastic tabs that are very easy to break. That said, even if you do break them (I did!), the result is not catastrophic and you should be able to put the panel back firmly where it belongs with no one noticing a thing. (Click to Enlarge) The TDS7000 Series Service Manual makes it sound easy enough: To remove the trim ring, slide the flat end of a soldering aid into the side slot on the trim ring. Press in, then lift up to hook it underneath, then pry up. And from the pictures, it’s as if you can remove the front panel without removing anything else. That just didn’t work… The front panel consists of multiple click tabs: 1 on the left side, 1 on the right and then a bunch at the top and the bottom. So far so good. However, the left and right side also have 2 slide tabs that go into the metal rails. If you lift the left and right tabs too much, these plastic slide tabs break off. So you need to be very careful to make sure that you don’t lift the plastic trim too much, and that you slide the panel out while it stays parallel with the display. Or… you don’t touch it: you can do all PC maintenance, including replacing the floppy drive, without removing the front panel. Scope Disassembly I will continue my tradition of documenting the disassembly of test equipment in too much detail because nobody else does it. Even though the service manual technically describes how to do it, a few pictures go a long way to make it easier. To access the inside of the scope, you need to remove more than 30 screws. On the plus side, they’re all Torx-15 screws and they’re all the same length, so you don’t need to worry about keeping track of which screw goes where. Still, it takes a while and it validated my recent purchase of this cordless screwdriver, recommended by Shrirar over at The SignalPath. Unbutton the accessory bag This took me longer to figure out than I want to admit: you can just unclick the bag from the chassis, but the buttons can be very tight and if you’re not careful the fabric can tear. Use a flat-head screwdriver right next to each button to lever it off. Put the scope upright on its back feet It’s an unusual arrangement, but the easiest way to