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Refurbishing a Tektronix TDS7104 Oscilloscope
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 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.