Could be some some permission issue...
Doesn't matter. I'll transcript the text (the pictures are at the end):
Tek 2215 - bringing an analog oscilloscope back from the death (again)
Paulo de Tarso Peres
Electronics Engineer
22 de março de 2023
This is my ‘new’ Tektronix 2215 scope.
I started to write this text two or tree times but something always interrupted me. So this history is about two years old.
I bought this scope on an auction site. It had a nice external appearance and a bargain price. The former owner told the voltage multiplier was missing and he was unable to find a proper replacement. He was giving up and selling the equipment.
So, cheap deal done, I bring the instrument to the lab and started to work. Here is what I found (and did):
The main power supply was dead and the repair attempt I found was unintelligible. The time/div switch had a disastrous repair attempt made with glue (that actually isolated the affected section from circuit). Even the fuse holder cap was lost.
Despite all those things, there was a chance of recovering. First of all, I needed to know if the CRT was still alive, and for that, I needed a working high voltage section.
It was the original problem because it lacked this part (actually, I don’t even know the appearance of this component). Fortunately, it was not my first dead multiplier.
Years ago, I discovered a manufacturer of some Tek voltage multipliers called Voltage Multipliers Inc. At that time, I was unable to obtain an original multiplier for a Tek 7834 I was restoring (the part was obsolete). Fortunately, their Design Guideline (
www.voltagemultipliers.com/wp-content/uploads/2018/08/Multiplier-Design-Guideline.pdf), the Tek 7834 service manual and the ‘autopsy’ of the old multiplier gave me some interesting directions. Long history short, I was able to build a suitable replacement.
Building a voltage multiplier is basically Electronics 101. The main constraints (and the ‘secret sauce’) are the voltage withstanding values of the components and the isolation between them. Since I only needed to test the CRT, I used some spare high voltage components from the 7834 to make a quick & dirt multiplier. Well, was dirtier than quick, but it worked (see the big green dot in CRT in the pics). Now I knew the tube was alive! And, most importantly: a restoration was technically feasible!
First point, I properly fixed the main power supply. A new electrolytic capacitor, some rebuilt PCB tracks and a new power MOSFET bring the supply circuit back. I also applied a pending service bulletin on the flyback transformer.
My next step was try to rebuild the time / div switch. But I had no success here. The last repair attempt made to much damage. Now I was hunting for a Tek switch 260-2023-00.
I was not inclined to make a Frankenstein switch (I confess the idea had an appeal… but no). So I managed to find a used one in an instruments repair shop in Sao Paulo. It costed little more than the amount I paid for the scope actually, but was a functional part. They also had the fuse holder cap.
Parts bought, I still needed to build a proper voltage multiplier (no Quick&Dirty this time) and find replacements for missing screws. From what I learned in the past and in the service manual, I designed a PCB for a new one and ordered it from JLCPCB.
I bought the proper HV parts (ok, I over engineered all of then, just in case). The red coating in the picture is a voltage insulator that I was willing to test. The label said 6500 volts per mm coated. Fair enough.
Thing built, scope assembled and turned on…
… and it’s alive!
A beautiful and bright trace, in all timescales, including delay!
And woosh! The filter cap at mains input smoked while I calibrated the equipment.
As with old HP equipment, this old Tek celebrates this 30+ years with a smoking cap.
Well… there’s no reason for panic. Just another replacement and voila: my Tek 2215 returned to its old glory!
Não foi fornecido texto alternativo para esta imagem
The beauty of analog... same signal and same scale in both scopes
I love these old analog Tek designs.
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