500 Series Oscilloscopes

The “brown” 535

This 535 ocillloscope with the serial number 3653 is definitely the oldest scope I have. I got it in April 1998. Because of the tube, a tek-made 5BGP2 crt (type 5BG and P2 phosphor, I guess ?!), with printed manufacturing date (8-53) on it, I would estimate the scope “birth” on late 1953 or 1954. This kind of tube seems to be a very early one, because even Stan is confused about the type used in this scope. ( A manual from 10-54 shows the well-known T51P2A tube) This scope is a instrument from tek´s “brown era”.
The housing of these instruments are not varnished with the common tek blue, but with brown varnish. Unlike newer models, this housing comes in one piece covering the entire scope exept the front panel. These early housing were welded together.

As the scope comes into my lab it was extremly dirty and I found that several tubes in the complex circuitry failed. The entire high-voltage muliplier was unsoldered and cables displaced. One of the well-known black high-voltage capacitors from Sprague completely failed and others seemed to have leakage currents far into the micro amps range :-\

The multvibrators in the main sweep failed and the unblanlanking circuit therefore was not armed - I didn´t even see a beam. Because I hadn´t a manual the work I suppose the work would take longer than life of the universe. Meanwhile I get a Tek 577 Curve Tracer and think about building a homemade tube test adapter. After finishing the work on that I put every tube out of the scope and perform dynamic tests on them. I cleaned all knobs with an ultrasonic cleaner and after I took all paper housings from the elevated caps, I washed the entire 535 in a big plastic tub.

Later I had the opportunity to buy the right manual, although the circuitry is all right and the serial number is in proximity compared to the scope, the type of the crt did not meet the crt of my scope.

The $10.000 question: Were are the pics of the working 535..? I work on this but I haven´t finshing the reassembly and further the recalibration...

You will see the working brown 535 - promised! But because of several circumstances the repair spanned over a period from beginning 2001 (!) - the above written first troubleshooting was the essence of that. It was a happenstance that the huge repair work was realized in 2014 - yes, there is no error in the text - it took me finally 13 years of doing the work...

2014 Tektronix marketing claimed a prize for the Oldest Scope in EMEA-market...

To be honest, I didn't realize this opportunity - so some nice volks from a well known Tek Distributor out of Hamburg put my nose on this ☺
This competition was two-fold: first you have to join a Tek quiz containing questions of "year of Tek's establishment" and "number of Tek's patents along the years". After successful doing the quiz you are invited to "prove" that YOU are the owner of the oldest scope in EMEA. You were asked to put a pic of the scope, some details of it and the prove-of-ownership...
So her we are: The prove of my working scope as a suggestion for the Oldest Scope

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