Repaired a 7A13: thank you TekScopes people


ik1zyw@...
 

Hello from a 100% silent member.

I decided to stand up and thank the active TekScopes crowd that over the years has shared useful information on fixing these extraordinary pieces of technology.



Last weekend I decided to try the 7A13 module into my R7603 chassis, after about 9 years of sitting in a drawer (because 7A18 plugins are more useful in my usual hobbyst activities). Ten seconds after power up the CRT collapsed into showing a bright spot, then nothing more, all lights were faint. I tried a re-plug but then nothing appeared and all lights were faint the moment the switch was pulled.



Then a search on the archives showed me the way: tantalum capacitors. I had to resort to the 7A13 manual to find C518 hidden on a side underneath a bunch of wires, which had turned "burnt brown". Replacing C518 was not enough, because that Vcc line was still measuring short circuit. Headed over to another tantalum, visually integer, and the problem was fixed. I still have one more tantalum in there to replace before it fails too.



Just wondering, and I probably know the answer: should I do preventive maintenance on 7A18, 7B53 and 7B50 as well, and replace tantalums there? Does the R7603 chassis contain tantalums as well? I haven't checked with the documentation for the chassis yet.




Had the 7A13 been unfixable, I would have re-used the digital display in some of my other projects. But now it stays there. I am wondering if someone in here has a surplus of displays up to 1970's that is willing to part with? Including the 4 digit display from latest 7A13. I've got lots of TIL305, but I doubt they were used in Tek instruments. In case, contact me off the list.




A picture of the burned tantalum is here <http://ik1zyw.blogspot.it/2017/02/tektronix-7a13-module-on-fire-almost.html http://ik1zyw.blogspot.it/2017/02/tektronix-7a13-module-on-fire-almost.html> . Few more thoughts on the subject will be published in the upcoming weeks.



Once again, a big thank you to the TekScopes community.

Paolo

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