Tektronix 502a Oscilloscope CRT Replacement
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- เผยแพร่เมื่อ 22 ส.ค. 2024
- This video covers replacing a Cathode Ray Tube in a 1965 Tektronix 502a Oscilloscope. The video also covers topics such as testing the oscillator section, and shows general cleaning and maintenance techniques.
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Nice to see, that you got this scope operating again. I got the same kind and use it now and then and just now. I got it about 1980 on an auction. It had a fault back then, in the main transformer. It got a separate winding to supply the filament of the CRT, and it have a voltage at about -2900 V. So there was some spark-overs in the transformer. I then mounted a small other transformer for this filament, and then it have worked since :). Well today I was using it, and I discovered that the light bulbs for scale illumination had finished. So I shall try to find replacements, and then I saw your video. The inscription on lamp is 6.5V .15A.
These vintage Tektronix scopes are absolutely beautiful, both inside and out. Pity that they're so rare in the former Eastern bloc (Poland etc.). I once had a ZRK OS-102 that was almost surely a copy of one of the Tek scopes, and it was a very nicely built behemoth that I wish I didn't have to sell... it took too much space in my then crammed room/lab and I needed cash to go to a concert I really couldn't miss, I think.
The things we do when young ;). I can’t tell you the amount of scopes etc I have bought, sold, traded, and then, regretted. Fortunately we live in a time with eBay and other sources. Hope the concert was great ;0). If they where so delicate and expensive to ship, I’d get ya one, but even here it is the same. I will only now get them in person, no more mailings here.
...eh....well....im in love, what a wonderful oscilloscope
I have one
I just wanted to say that I have really enjoyed your video on the Tektronix 502A scope! A great pleasure! And glad that you kept this from the audiophools that would have been more than happy to rob this scope of its tubes for the 5AR4 rectifier tubes and any 6DJ8 and 12AU7 tubes as well. I have a few different Tektronix scopes on hand. Let's see here, I have a 503, 504, 533A, 535A,2- 545A, 2- 561A, 564 storage scope and a true dual trace 565 scope! One thing I would suggest is to keep an eye on those electrolytic capacitors, I had my 535A for almost 30 years and used regularly and one day, 1 of them decided to turn into a dead short and took out the 10 ohm resistor, bridge rectifier and the power transformer. I was lucky enough to have a 535A parts mule to replace that power transformer. After that, I ended up replacing ALL electrolytic capacitors.
Wow, quite a collection! Last month I also picked up a 585A, awaiting a restore before the end of the year. Hoping to locate a spectrum analyzer plug in just for fun. These scopes are addicting to work on, too much fun! Thanks for the reminder of the e caps, I am defiantly going to replace them in all these units. Time, oh how I wish I had 28 hours per day….
@@savvycircuits9683 Nice on saving that 585A! I have always wanted one, but seems like I can only find them on eBay most of the time and the last few scopes I got from eBay ended up getting destroyed by FedEx. I had a pristine 531A until the delivery driver decided to drop the package out of the back of his truck. Needless to say, the CRT was destroyed and the entire scope was bent out of shape from being dropped onto the front. But yes, these scopes are so much fun to work on and even more fun to use! Nothing like the feel of a real switch, humming of the fan and seeing the trace on a CRT! I did have a Tektronix 2465 scope but that scope was no longer usable. The Dallas chip with the battery backup died and rendered the entire scope useless as it held all the calibration. But I hear ya on time......never seems to be enough time......
Also, Tektronix made several spectrum analyzer plug ins. 1L5 is the one you want to look for if you want the audio frequency range. I don't have any myself, but there were a few covering a certain bandwith.
Outstanding
I had a similar broken centering ring on one of my 502's years ago. A delrin washer and some JB weld fixed it. That was 20+ years ago. These scopes are not used anymore but were great for audio work.
Yup, that’s me. Most;y for audio here. Thanks!
Nice video! There was a 502 (not sure if it was a "A" or not) that was at a startup company I worked at in the late 80s. The founder/boss had got it along with some other "junky" stuff from his last employer I think. My recollection is it had some problem and maybe only 1 channel worked. It got put into a storage room and most likely ended up in a dumpster years later after I left. It had a light shield on the CRT bezel and I think there was even a rubber face visor so it must have been used someplace with a lot of ambient light and glare.
I have never been totally clear on the usefulness or applications for the dual beam feature on these.
Great Job. I have restored my 502A some time ago too. Although both are 502A, there are some differences. My model originally had no PCBs inside and therefore I assume your model is newer. At 41:31 I can see that you are missing the "CRT CATHODE GND" contact plate (Part NO. 386-427) which should be closed during normal operation according to the manual page showing the CRT CIRCUIT.
Good eye! Thank you so much, I did not notice this, though now I see it on the schematic. By chance do you know the feature thought here? My guess is if you wanted to add an external signal directly to the CRT via the pin access as described in the manual. Although I cannot seem to find a referenced wording of the grounding plate.
@@savvycircuits9683 Thanks, but that was pretty easy for me since it was missing on my oscilloscope before restoration too.
You should find the description (and the purpose) in the chapter "Modulation of the track brightness (intensity)". In the service manual downloaded from the Internet it's printed on page 2-10 and in my paper manual on page 2-11. Tektronix refers to the plate as the "ground strap on the back of the instrument".
@@jaroslawkolacz5610 Yup, found it! I actually had an apparently early 502a manual, as there are 2 I guess. I just got the correct one now that lines up with your notes. I see the use now. I am just going to make a bar from some conductive steel. I recently saw a 585 for only $200 on Facebook Marketplace. I may have to scoop that up!
@@savvycircuits9683
I like your new CRT :-) My 502A shows blue traces without persistence on white background.
I think there could be even more versions of the manual ...
In my opinion the original grounding strap is made of plated brass. At first I had the idea to make a replica as well, but then I asked a man who sells a lot of old Tektronix parts on eBay. He told me that it was not worth the time to set up the auction and describe this part as its value is only a small fraction in comparison to the shipping costs. However, if I buy another part from him, he will include it for free. He also gave me the opportunity to pick it up personally. In this case I could get it for free without having to buy anything else.
I think it's worth a try in your case too.
And I'm looking forward to the 585 video. :-)
@@jaroslawkolacz5610 Agh yes, the beautiful blue traces! These where made with this phosphor so camera's of the era could take more detailed photos of the screen. As it turns out, green is not as photographable.
Hi, i have a 502a too, and during the shipping crt broke, can anyone tell me where i can find one? Thanks
Great video! Just out of interest- is that a P2 or P11 phosphor in the CRT?
It is p11 friend. They used this blue hue for taking photographs. Turns out blue is more detailed in photos than green. I just picked up a 585A, and it has p2, green color.
Hi, I bought a Tektronix T502A oscilloscope and unfortunately the screen broke during shipping. There is a type T-5021-11. I want to ask if you have such a screen for sale. Well thank you. Peter, Slovakia
I do have one if you need. Please contact me at rickosey2@yahoo.com and we can see if I have the proper part number. Are you able to see the part number on the CRT? It is important as I have discovered not all 502A had consistent CRT models.
OK i don't know why it keeps getting removed but i keep trying to post where i found the clamping ring.
it was on esty
just search for tektronix oscilloscope 500 series
I would love to help you out - I can design and print. B McFarland can get us in contact!
ok cool. Brad has reached out to me, I will be in contact.
Great job on this btw. I have had the unit running for some many hours, and the PLA is withstanding. Average heat inside is roughly 95-98, though in an air conditioned room.
Great video.
I have a friend that might be able and willing to 3d print the retainer ring/bezel, I have a message out to him.
That would be cool!
Thanks for getting Kevin and I together on this 3d print. A wonderful job by him...:)