New Scope Day

A project log for Microhacks

A collection of small ideas

Ted YapoTed Yapo 12/16/2018 at 16:350 Comments

I measured very, very carefully and determined that a hacked Tektronix TDS754D would, in fact, fit down my chimney :-)  It turns out that Rigol wasn't the first to sell (almost) the same hardware as different scopes: the 500 MHz '754 can be hacked into a 1 GHz '784 by removing a few capacitors.

The one I found had already been "fixed," so it was ready to go.  To check the bandwidth, I scoped the tracking generator output from my spectrum analyzer which goes to 1.5 GHz, and is pretty flat, amplitude-wise.  Set to zero-span mode, the analyzer makes a nice sine-wave generator. I first measured the amplitude of a 100 MHz output at 712 mVpp, then cranked up the frequency until the amplitude dropped by 3 dB (= 0.7071 * the original amplitude).  The number to hit was 504 mVpp, and I found it at 1.05 GHz, right where it should be for a 1 GHz scope :-)

This is an old scope - it uses a 3.5" floppy to save data.  I had to order a USB floppy drive ($12), which surprisingly is cheaper than a box of disks ($20).  Luckily, my spouse found a few disks in an ancient laptop bag.

I happened to have a 640x480 LCD monitor from around 2002-2003 that still works, and it hooks right to the VGA output of the scope, so I'm protected if the CRT goes bad.

I dug through the "Q" box last night and found my bag of 2N2369 transistors, so I can make an avalanche pulse generator and check the rise time, too.

This is my first Tek scope, even though it's an old one.  So far, I'm very happy with it.  It even has that "old electronics" smell -- kind of like the old-book smell first-edition collectors relish.