Tektronix 7000 series ramblings

My 7000 series collection got a bit boost yesterday when I went to pick up my Ebay winnings.  What started as a pickup for a Tek 551 dual beam scope ended as a trunk full of Tektronix booty.

7834 Mainframe
I picked this up about a year ago (coincidentally from the same same guy).  It was host to my only plugin, a 7D01 Logic analyzer + DF1 display formatter.  The 7834 is a great 400Mhz mainframe, but completely wasted on the 7Dxx plugins.  In fact, the higher bandwidth is in part possible due to it’s rather diminutive screen, making it pretty much the worst host for these plugins.  I decided it was time to give this frame the plugins it deserved, so I picked up a 7A26 200Mhz vertical and a 7B80 timebase, which is triggerable to 400Mhz, and sweeps down to 10ns.  Both work flawlessly in the 7834.
Here it is running the 7D01 a few weeks ago.  I’m using an EPROM reading arduino program to generate the counting pattern.

7603 Mainframe
I actually owned one of these about 24 years ago and ended up selling it.  I ended up buying a 7603, along with the above mentioned analog plugins, plus a 7D20 for a totally reasonable price.  He even threw in a few 7D01’s for parts.  Sweet.

This 40 Mega-sample per second digitizing scope, like all of Tek’s ventures into new territory, was a groundbreaking piece of hardware for 1980.  It works amazingly well for a 35 year old piece of gear, with the exception of an Error 54 which shows up on self test.  The service manual identified this as a waveform RAM error (specifically U410), which explains the few missing samples on captured traces that always show up in the same place.  Fortunately, I have a stash of the venerable 4116 RAM chips.  Unfortunately, they’re not socketed on the 7D20, and I’ve yet to
Unsurprisingly, the documentation is superb, and the theory of operation makes for an interesting read.  The RAM error is easily overlooked for now, but figuring out how to test 4116 RAM chips seems like it could make for an interesting project.  Another worthwhile project might be a fan-base for the 7603, as the 7D20 really cooks in this passively cooled frame.
Here’s the offending RAM chip.  No glaring physical maladies, but it does look like this board has seen a service bench before


Here it is showing the output of my Precision E-75 signal generator, which I fired up for the first time ever today (after checking the caps & rectifier of course).  Obviously it needs some work (the E-75) , but the measured frequencies are within a few % of what’s shown on the dial.  Note the pixel hanging below the lower trace at the 6th division, that’s due to the RAM error.


It’s a fairly capable machine.  Of course a $300 cheap Chinese POS would blow it out of the water, but this is way more satisfying & fun to operate.  I really enjoy helping keeping the history of these pieces alive in whatever way I can.  Beats TV, and it keeps me off the streets.

My adventures with this old dinosaur are chronicled here


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