Hello everyone,
let me introduce myself for my first post, is there a special part of the forum to do this? I'm a student at the TU Delft in The Netherlands. My specialization is in Mechanical Engineering, but my heart is in Electronics. I plan on doing a Masters in Mechatronics or something similar. My passion has started after a project in Mechatronics in which I had to relearn a lot about electronics, about a year ago. While I was doing this I stumbled upon the EEVblog on Youtube. I've been hooked ever since. My English is not terrible, but please correct me if I make any grave errors, I can always learn!
In this time I've done a few projects and build some stuff. While building a small collection of devices and components I decided to acquire an old Analog Oscilloscope. After some searching on Marktplaats (our local Ebay) I found a good and working Tektronix 465 oscilloscope as well as a Newtronics 200MSPC AM-FM-Sweep/Pulse/Function-Generator (their words, not mine), about which the internet knows nothing at all. All in all I paid 95 euros for both, the guy was happy to see it part with someone who was enthousiastic and I got a brand old scope!
After some playing around I decided to stress test the scope by leaving it on for about two hours straight. It still functioned but ran quite hot (as I would expect is normal during operation). The next time I turned it on: Nothing. No trace, nothing. Fearing for the CRT I bashed the Beam Finder button and saw a glimpse of green. The CRT was safe. Queue the DMM and voltage check. The -8 volts was only reading -6. Bingo. I would've liked to run the signal through an oscilloscope to check it for irregularities, but I only have one
. I was able to find the original service manual from artek manuals and bought it for about 4 dollars, as it would help a bunch. Then I left the project for a month or two, because I was scared of breaking stuff and the -2450 volts segment right besides the -8.
I wanted to fix the issue without having to take the entire thing apart, which can be a pain, so I wiggled the rectifier until it fell off. I could now measure the AC volts and attach a new rectifier, with amps measurement in between. I measured 11 volts AC (the coil produces power for a +5 rail and a -8 DC) and 500 mA, so this was all okay. I decided to tackle the big Filter Cap (labeled 1977, which is older than I am) 3000 uF worth. After some 'percussive maintainance', I was able to desolder it without damaging the board too much. (I managed to take one trace off entirely) I replaced it with a local dealer's 3300 uF, which should be okay. I also replaced the bridge rectifier, as I had broken it myself. (It was still okay diode-wise)
The result is a working Oscilloscope, which is only a bit out of cal. Notice the replacement wire and new Rectifier!
Bonus Newtronics generator, about which I will post some questions later!
Thanks for reading! Hope to keep learning from everyone of you, because I couldn't have done this without you, especially Dave)