Filed in Engineering and Inventions on Friday, March 28. 2008

Tektronix 547 Oscilloscope—Getting an Old Soldier Back in the Fight

Of all the 500 series modular scopes made by Tektronix, the 547 is one of the most desirable due to its 50 MHz bandwidth and innovative dual timebases. When released, this machine was way-hot high tech, crammed with a mix of vacuum tubes and discrete semiconductors, and worth as much as a new car. I got mine through a friend who found it at a church rummage sale and paid $10 for it, complete with cart, some extra modules, and manuals for everything. Any problems? Well sure—the thing's been in service for 40 years, knocked about by at least two private companies (judging by the calibration stickers) and its original owner, the United States Navy. A short list:

The dust filter that covered the fan was missing, because the bolts that kept the bezel on were sheared off—though the bezel came with the scope in the drawer of the cart, at least.
The original power inlet was cracked, and missing its ground pin, which is more than a little dangerous.
The fuse holder was chewed up and unable to retain the fuse and cap, which was missing entirely.

The mangled power connector (first photo) I replaced with a Hubbell miniature twist-lock connector, which was the only thing I could find that would fit the hole in the chassis. I had to file out the holes on the connector a bit to make the bolts fit, however. The second photo also shows the new fuse holder.

I fixed the dust-filter by buying a package of 12 inch square “StrataDensity” fiberglass filters and trimming them a bit to fit into the filter bezel. I can't say these have the best dust-filtering performance, but they're certainly better than nothing. I also cut two plates of expanded metal grate to sandwich the filter in the bezel, keeping it from being sucked into the fan or from falling out of the back. The bezel is now attached through the original bolt holes (I haven't made hard modifications to anything that was original to the scope, out of respect for history) by means of two standoffs and small 4-40 screws.

These small fixes are all I needed to get the scope up-and-running. I don't yet have the signal sources necessary to really calibrate it properly, but it's good enough as it is and works well for the mostly-qualitative measurements I've been doing lately. Now all I need is a bottle of painkillers for the chronic back pain I'm sure to acquire lugging this boat-anchor around. ;)

Six Comments So Far

February 07, 2010

Steve Holden says:

I have one of these beasts and still use it on my maintenance bench. It still works well but to save space I will soon reluctantly have to replace it.

Regards Steve

May 18, 2011

peter meff ert says:

I have its sister model the RM547 (rack mount) which is even heavier (29.9 kg = >65 lbs) but it is still in good operational order,
after more than 40 years I had a hard look at all the tube pins and holders, pins needed cleaning, a 'dremel' tool came in handy.
clean all pins, a squirt of switch cleaner (with lubrication) just before re-inserting the tube AND PRESTO, nice and stable again,
a pleasure to work with.

one a personal note: I am almost 84 years old, retired scientist, did most of my electronic work in the analog age, play a lot with my computer, prefer WIN-XP and still build the occasional gadget when needed

July 26, 2014

Pete Lancashire says:

Thanks for keeping a 547 vs. stipping it for 'audio' parts.

BTW The man pretty much credited with designing the features of the 547 just passed away Bob Rullman.

And if something tells you that your nuts for keeping such a oldie

http://readingjimwilliams.blogspot.com/2012/02/vintage-scopes-are-better-part-1.html

-pete

September 19, 2014

Eiki Martinson says:

Thanks for your comments gentlemen!

November 03, 2015

carl says:

Just carried home a vintage 547 from local college laboratory... Tomorrow will start to inspect it and have firt cares...
Will look ahed if will need some help to fix it, hope not ;-))