Introduction

A little over a month ago, I ran into a Tektronix TDS7104 at the Silicon Valley Flea Market, where else?

TDS7104 in the trunk of my car

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.

TDS7104 at first power up

But when I tried it again a few hours later, it got stuck at the BIOS screen with a CMOS battery error.

TDS7104 bootup 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.

TDS7104 with advanced jitter analysis license

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)

TDS7104 Apple TV Remove measurements

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:

  1. PC motherboard CMOS backup battery dead
  2. PowerPC backup battery dead
  3. Hard drive dead
  4. Power supply capacitors leaking

I was lucky and only had to deal with issues 1 and 3, sort of.

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!

TDS7104 hard drive sled

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.

TDS7104 HD out of sled

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.

CR2032 on motherboard

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

Display Settings

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:

Windows gamma settings control

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.

Service manual figure 6-3: Trim Removal (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

Remove 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 dismantle the scope is by putting it on its back feet: you don’t need to remove any screw from the back!

TDS7104 on its back feet

Let me once again sing the praises of a sturdy equipment cart: it’s so much easier to walk around the cart than to muscle around bulky, heavy test equipment on a table.

Remove the top panel

4 screws through the accessory bag buttons (“snap studs”) fix the top panel to the chassis.

TDS7104 remove top panel

After removing this panel, you could remove the side panels already, but I found it much easier to remove the bottom panel next.

Remove the bottom panel and loosen the black front connector trim

Next, remove the 5 screws of the bottom panel as well as 3 screws that keep the black trim of the front BNC connectors in place.

TDS7104 bottom panel and connector enclosure

The black trim doesn’t need to be completely removed, only loosened because otherwise it will soon be in the way of some other screws.

The bottom panel shall now be removed though. Just slide it down a bit and take it off.

In the picture above, you can see 2 screws that aren’t marked in red. That’s because they don’t keep the bottom panel in place. But if you feel like it, you might as well remove them now too.

Remove the handle and side panels

TDS7104 side panel with handle

With the bottom panel gone, the side panels are a breeze to remove after unscrewing the handle.

I lied: these 2 screws are different than the others. But they’re a different color and impossible to get wrong.

Remove the 2 sheet metal parts

With the outer covers removed, you’re now staring at the sheet metal RF protection enclosure. It consists of 2 parts, each part covers 2 sides. Remove all the screws, take off the bottom part and then the top.

TDS7104 sheet metal top

TDS7104 sheet metal right

Note how some of the bottom screws are hidden underneath the BNC connector cover. That’s why you had to remove its 3 screws of the black trim.

TDS7104 sheet metal bottom

TDS7104 sheet metal left

Congratulations! For those who didn’t keep track: you’ve removed 32 screws!

After removing the panels, you now have access to the acquisition board at the bottom and the PC motherboard at the top:

TDS7104 acquisition board

TDS7104 PC motherboard

One side has nothing but cooling fans, but from the other side you can see the power supply and an RS-232 port that you will need to connect if the backup battery of the PowerPC controller board expires.

TDS7104 right side

If you need access to those items, you’ve only done the easy disassembly part. On my unit, both the PSU and the controller backup battery were fine so I was done.

Note on the picture above that the front panel has been removed. You do NOT have to do this for pretty much all restoration cases! And you really shouldn’t.

Reinstall the bottom sheet metal cover

All of my work on the scope was on the PC motherboard and I had to put the scope back in its horizontal position. To make sure that I didn’t accidentally damage the acquistion board, I put the bottom sheet metal cover back in its place.

TDS7104 bottom sheet metal back in place

A Failed Attempt at Switching over to an SSD

I’ve been using CompactFlash cards in the past to replace ailing hard drives. They work, but unless you buy a more expensive “industrial” card, they don’t have built-in wear leveling support. That is not a problem on a Rohde AMIQ that runs DOS, but on an OS like Windows with swap space, it could be4. So this time, I chose a 64 GB mSATA SSD ($35) and an mSATA SSD to IDE 44 Pin 2.5” adapter ($15)5.

64 GB mSATA SSD and IDE converter

The standard way to move away from a failing hard drive to an SSD is to once again use HDD Raw Copy Tool to write the image to the SSD and that is that. I tried that with the 64 GB SSD, and while the scope got past the first-stage boot process, it errored out during the second stage when it tries to bring up the Windows GUI with a STOP: c0000218 {Registry File Failure} error.

Registry File Failure

Older systems often had issues with partitions larger than 32 GB, so I bought a 32 GB mSATA SSD instead, $3 cheaper for half the capacity, but I got the same error.

Just copying the drive image to an SSD worked fine for others, but for me it was a dead-end that I spent many hours trying to get around. I eventually decided to reinstall all the software from scratch, which was a whole other adventure.

Reinstalling from Scratch: Windows 2000 Pro or Windows XP?

I had wanted to avoid reinstalling the OS from scratch because I expected to run into a bunch of driver issues, but in the end I had no choice. While a number of people have reported that Windows XP can work on some of the TDS7104 motherboards, I decided to stick with Windows 2000 Pro because I know that works and I didn’t have a pressing need for more functionality, whatever that might be.

The scope has Windows 2000 Pro Embedded, but I wasn’t able to find an installation disk for that and the regular version works fine too. The ISO file can be downloaded from the Internet Archive.

The license key that’s printed on the back to the scope does not work with the regular Windows 2000 Pro. The Internet Archive one has a key that works, and other valid keys are just a Google away, but I didn’t even need one: I was never asked for a license key during the Win2k installation on the scope.

The standard way to install Win2k Pro is with a CDROM drive. Unfortunately, the drive didn’t work which meant I had to open the whole machine again to install a replacement drive.

Not All TEAC CD-224E Drives are the Same

The TEAC CD-224E laptop drive in my TDS7104 got detected just fine by the BIOS and in Windows, but when you inserted a disc in the drive, neither the BIOS nor Windows could read from it.

Since the RadiSys motherboard doesn’t support booting from USB stick, I decided to replace the TEAC CD-224E laptop drive with a ‘new’ one that I got from eBay for $20.

Unlike the hard drive, the CDROM drive can’t be removed without opening up the TDS7104, but once the case is open, the effort is minimal. I first removed the floppy drive to have a bit more maneuvering freedom with the cables, but it’s not really necessary.

Unplug the CDROM IDE cable

CDROM IDE cables

Remove 2 screws

CDROM screws

The CDROM drive sits in a metal enclosure with a small adapter PCB that converts the CD-224E 50-pin slimline IDE connector to a standard PATA/IDE connector.

Old and new CDROM drive and converter PCB

I tested the broken drive with the adapter PCB and my USB-to-IDE dongle on my laptop to make sure the issue was with the drive and not the CDROM disc, and that didn’t work, as expected. With the new CD-224E/dongle combo, my laptop could read the installation CD just fine, but when I installed the new drive in the TDS7104, the BIOS couldn’t even detect the drive! I tried every BIOS setting under the sun, but no luck.

There are many versions of the CD-224E, all with the same dimensions and slimline IDE interface, but clearly they don’t all behave the same. The version of the broken one is version A93 (2000), the new one is CD0 (2005). You can find A93 drives on eBay, but $69 is way too high for something that I’d be using exactly once.

Installing Windows 2000 Pro on an Old Machine through a Virtual Machine

(Another dead-end)

It is allegedly possible to install Windows 2000 Pro on an old machine without CDROM and USB port by using a virtual machine. The process is convoluted:

  • mount the installation CDROM ISO and the SSD onto the virtual machine.
  • go through the first phase of the installation process until asked to reboot.
  • now move the SSD to the old the machine (the scope) and proceed with the installation there.

I once again spent a few hours getting this to work, but the scope never managed to make it to the Windows installation GUI.

Burning the Windows 2000 Pro Installation Disk onto a USB Stick

Alright, so I’m running out of options and USB is about the only storage interface left. The scope can’t boot from a USB stick directly but there is a way around that.

Let’s first create a bootable USB stick with the Win2k installation ISO on it.

Most of the time, you can use a utility like Balena Etcher to burn a CDROM ISO onto a USB stick, but of course that doesn’t work for the Windows 2000 Pro installation CDROM.

Instead, you need to use WinSetupFromUSB to prepare the USB stick:

  • Download, install, launch
  • Select the USB stick as target
  • Select Auto format with FBinst and use the FAT32 file system
  • Add to USB disk: Windows 2000/XP/2003 Setup
  • Select the mounted Win2K Pro ISO drive as source
  • Press “GO” to copy Win2K Pro onto the USB stick

Booting from USB Stick with a Plop Boot Manager

Plop Boot Manager makes it possible to boot from a USB stick on machines that don’t support it.

It goes like this:

  • copy the plpbt.img image from the plpbt-5.0.15.zip archive to a floppy disk with a tool like WinImage, Rawrite32, or RawWrite for Windows.6
  • boot the Plop Boot Manager from floppy disk.
  • the boot manager has a USB mass storage device driver
  • select USB as boot device

I tried hard to avoid the floppy disk route because my experience with floppy drives on old test equipment has been abysmal: none of them worked. Having no choice, I tried to copy the boot manager image with my USB floppy drive and… that didn’t work either. All these years the USB floppy drive, freshly bought from Amazon, was the culprit!

Since the scope still worked fine with the IBM HD, I used its own floppy drive to put the image onto the floppy disc and that worked.

Plop boot manager selection menu

After setting the BIOS to allow booting from floppy, the scope booted into the Plop Boot Manager just fine and it was able to boot the USB stick with the Windows 2000 Installation ISO.

Plop doesn’t support USB hubs. The RadiSys motherboard has only 1 USB port which will be occupied by the USB stick, so you’ll at least need a PS/2 keyboard to do anything.

Installing Windows 2000 Pro

With the empty 32GB SSD plugged into the scope, the installation of Windows 2000 Pro was uneventful. There are 2 phases: the first one uses text mode and primarily copies all the necessary drivers onto the SSD. The machine then reboots and continues the installation in Windows GUI mode from the SSD, though the USB stick is still needed in a later stage.

The TDS7104 has a bunch of specialty hardware that needs dedicated drivers, but those are not needed to get the OS up and running.

At long last, I was able to see this image:

Windows 2000 Professional installation complete

Installing Special TDS7104 Drivers

There is a great GitHub repo with a bunch of TDS7000-series software, including this Drivers directory. The README.md says that the driver should work for Windows 98 and XP, but the Chips and Technologies video driver definitely did not work for Win2k!7

I used Driver Collector to extract drivers from the original hard drive and that worked fine. You can find these drivers here.

Device manager missing drivers

The 4 specialty drivers are for these components:

  • Front panel

    This is the USB Device that’s listed under “Other Devices”

  • Texas Instruments PCI-1225 CardBus Controller

    You need to install this driver twice, once for each port. Windows installed a default PCI-1225 driver for this, but that one doesn’t work, hence the exclamation mark next to it. The name of the driver .inf file is unsup.inf, for unsupported? Confusing, but that’s the one to use.

  • PCI2PCI bridge

    That’s the Other PCI Bridge Device.

    Other PCI driver

  • Chips and Technologies 69000 video driver

    The default Windows driver for the C&T 69000 is what makes the screen work when running Windows, but it’s not sufficient to render measured signals in the TekScope application. For that, you need to update to the Chips and Technologies (Asiliant) 69000 driver.

    C&T driver selection

Installing Tektronix Firmware

The TDS7104 and TDS7054 firmware v2.5.5 can be freely downloaded from the Tektronix website. The installation was painless, just launch the executable.

The TDS7104 has a convoluted architecture where the PowerPC on the controller board can access files on the hard drive of the regular PC that are located in the c:\vxboot directory. Since the controller backup battery on my scope was still in good condition, I didn’t have to do anything special: the vxboot directory was created automatically during the firmware installation.

One thing that was missing, though, was the advanced jitter license option.

The Scope is Working!

And with that, I finally had a working TDS7104 with SSD!

TDS7104 with IBM Travelstar in front

The time from pressing the power button to having a waveform on the screen was much lower too: from 2min50s down to 1min35s.

Re-enabling the Existing License

The same GitHub repo that I mentioned earlier also has an unlock options directory with scripts to enable and validate license key features. On the Eevblog forum, plenty of people have been able to use it, but it’s not as user-friendly as other license key schemes.

Most of the time, license keys are additive, with one license key per feature that must be enabled. On the TDS7104, there is 1 license key that enables all features at once.

The validate script shows how that works with the license key and serial number of my scope:

./validate.py BREHZ9885D3MNKXHHYQCQRGQRW7C

E1 91 73 BF F7 7B E4 C5 52 3D C7 3A E1 9E 71 8F 76 01
44 2F 54 00 00 C0 1B 79 48 00 00 00 00 00 00 00 00 A8 16 30 00 10 00 00 00 00 00
This key is for UID 1BC00000542F (S/N 21551, model TDS/DSA/DPO7104):
CRC: 4879
Key is valid, active options:
00 00 00 00 00 00 00 00 08 00 00 00 00 00 00 00 00 00

We can see how that long string of gibberish contains:

  • the serial number 21551
  • the model number TDS/DSA/DPO7104
  • a UID that is really just a combination of the serial number and the model
  • a CRC
  • an 18-byte or 144-bit bitmask

I can recreate the license key by feeding these parameters back in the generation tool:

./gen.py tds7104 B021551 000000000000000008000000000000000000

XBGDV-K8GDM-KH7X3-979Y9-ZZ593-9ZRZZ-4837X-9VV5Z-T9HB

I had to join the 18 bytes into one 72-digit hex number.

The license key that comes out doesn’t match the original one, but after entering it into my scope, it worked just the same:

New Jitter Analysis - Advanced license

The scope is very forgiving about the license keys: upper case, lower case, dash or no dash, it all seems to work. You can even reduce the number of hex digits in the license enable mask to a certain extent, and the license key will still work:

./gen.py tds7104 B021551 000000000000000008000000000000

7GWUZ-RRRMK-59LYT-978Y8-GZD93-8ZQGZ-C836X-8CVD

What remains is the question which bit maps to which feature? This post in the eevblog forum has you partially covered here:

########################################################################
4   
# options masks/names/descriptions, conversion functions
5   
6   
# 01 - 1M
7   
# 02 - 2M
8   
# 04 - 3M
9   
# 06 - 2M 2A
10   
# 08 - 4M
11   
# 00 00 00 00 00 00 04 - USB
12   
# 00 00 00 00 00 00 20 - JT3
13   
# 00 00 00 00 00 00 00 80 - ET3
14   
# 00 00 00 00 00 00 00 00 08 - JA3
15   
16   
# 00 00 05 00 00 00 00 00 00 10 - ASM DDRA DJA
17   
# 00 44 00 00 00 00 02 08 - SM ST J1 J3E
18   
# 04 40 00 00 00 00 06 C0 10 - 3M JT2 USB2 ST
19   
# 04 44 FF 03 00 00 8D A3 EF FF 17 - 10XL, MTH, PTH1, ASM, LT, DDRA, SLE, EQ, TDSDDM2, TDSUSB2, YDSCPM2, RTE, IBA, PCI, TDSDVI, TDSET3, SAS, TDSHT3, TBD, JA3, TDSPTD, TDSVNM, DPOPWR, TDSHT3v1.3, 73, 74, DJE, DJA, 77, 78, 79, SVE, SVP, SVM, SLA

Note how JA3, advanced jitter analysis, indeed has bit 14 set to 1.

Some people just use a mask of FFFFFFF....FFFF.

Some of these analysis tools can once again be found in the same GitHub repo, or on the Tektronix website.

Jitter Analysis - Advanced tool

This is all theoretical, of course. I don’t think I’ll ever have a hobbyist need for any of this…

Cleaning Up

The final act is cleaning. This scope was in exceptional condition, except for the knobs on the control panel.

Dirty knob and less dirty one

The knobs have a thin anti-slip layer on them that is a finger grease magnet. Removing that layer with isopropyl alcohol makes the knobs look like new without a noticeable difference in control. Just be careful about using 99% isopropyl, I think it attacks the plastic. 90% was fine.

Peeling dirty knob

If some knobs are missing or cracked, the ones of a TDS220 are identical. You can buy knobs new or on eBay, but they’re expensive. If you really need a few, you might be better off buying a donor TDS220 instead.

TDS220 on top of TDS7104

The End

And with that, the scope is ready to be deployed to a shelf in my garage. One day I’ll need something with this kind of firepower but for everything else, a small scope with lower specs is way more practical. I like the scope better than the Agilent 54831 so that will probably hit Craigslist at some point.

All words in this blog posts were written by a human.

References

Footnotes

  1. I obviously only figured this out after removing the enclosure… ↩

  2. I didn’t try the 16-bit not-so-true color mode. ↩

  3. The Agilent 54831 uses a similar overlaying method. ↩

  4. In reality, I will never use this scope enough to ever run into an issue like this. ↩

  5. You can still find native 2.5” IDE 44 laptop SSDs, like this one, but you pay $30 more for the same capacity. ↩

  6. RawWrite for Windows is the one to use on a 32-bit Windows system, like the Win2k OS on the IBM Travelstar of the scope. ↩

  7. If you install the incorrect driver, the scope will still boot with a working LCD screen, but once the Windows GUI starts, it will move its business to the Intel integrated GPU. You need a VGA monitor to follow what’s happening. Even if you later select the right driver, Windows somehow thinks that the old driver is good enough and just doesn’t do it, without any feedback. I had to manually delete the bad driver files from the SSD to finally make it work. ↩