Musicmanager
Well-Known Member
.. .. .. with my Oscilloscope
Hi Guys
If you've been watching the posts recently you may have noticed that I've recently acquired an old oscilloscope. It's an Advance Gould OS4000 and is currently working well. However, I've been systematically stripping, cleaning and re-seating the inside components, PCBs etc to get rid of the piles of dust that had accumulated. I discovered a problem with a large crack in the plastic back panel which I've nearly solved and in the process of doing that I've noticed something that I'm worried may be a problem about to happen.
One of the PCBs, labelled Store and Timing Logic, is populated with a significant number of IC's some of which I cannot see properly but most seem to be 74S74 flip flops most of which show no signs of any problem that I can see, but two of them close to the warm embrace of the PSU have what I thought were discoloured pins but when I tried to scrape a bit I discovered the 'colour' is a dark blue jelly/grease which would clean off. Also alarming, there is a large black ceramic capacitor very close to these two ICs which has bubbles in the surface. There are several of these visible in different areas on the board, none of which have a smooth surface so there may not be problem ? The parts list shows them to be 0.1uf ceramic caps 30v +80% -25%.
I've tried to take a picture to show you but it's difficult without getting the boards out of the unit which I haven't attempted to do yet.
Any advice would be very much appreciated.
Thanks
S
Hi Guys
If you've been watching the posts recently you may have noticed that I've recently acquired an old oscilloscope. It's an Advance Gould OS4000 and is currently working well. However, I've been systematically stripping, cleaning and re-seating the inside components, PCBs etc to get rid of the piles of dust that had accumulated. I discovered a problem with a large crack in the plastic back panel which I've nearly solved and in the process of doing that I've noticed something that I'm worried may be a problem about to happen.
One of the PCBs, labelled Store and Timing Logic, is populated with a significant number of IC's some of which I cannot see properly but most seem to be 74S74 flip flops most of which show no signs of any problem that I can see, but two of them close to the warm embrace of the PSU have what I thought were discoloured pins but when I tried to scrape a bit I discovered the 'colour' is a dark blue jelly/grease which would clean off. Also alarming, there is a large black ceramic capacitor very close to these two ICs which has bubbles in the surface. There are several of these visible in different areas on the board, none of which have a smooth surface so there may not be problem ? The parts list shows them to be 0.1uf ceramic caps 30v +80% -25%.
I've tried to take a picture to show you but it's difficult without getting the boards out of the unit which I haven't attempted to do yet.
Any advice would be very much appreciated.
Thanks
S
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