I have had this scope for about 3 years now. I bought it working.
After about a year of use, it developed a problem where it would reset itself randomly while in use. After a while it would keep cycling, seconds between resets.
The trace also tends to go to the maximum value when this happens too; I believe this is because the analog supplies were going out of tolerance.
Initially, I gave it a good clean and sprayed contact cleaner on the main connectors. That fixed it for about 2 years...
And now, it's doing the same thing... but cleaning hasn't fixed it...
So the question is what causes a supply to act like this? Why would it work fine for 2 years after cleaning it? What did the cleaning fix?
This is a very old supply. The scope was manufactured in 1993. The supply is capable of about 200W and is air cooled by a fan at the rear. (The fan also cools the rest of the instrument.)
It looks like a single power NPN forward with a very large transformer. Picture attached.
The supply is controlled entirely in discrete logic, as well as an LM339 comparator. There are no actual SMPS controller ICs anywhere on the board.
All caps are Chemicon or Rubycon.
This is a very nice power supply and an example of sheer overengineering. Look at the sheer number of capacitors on just one rail - 8 x 35V 1000uF (for the +15V supply, which runs the CRT and fan, and nothing much more.) On the +3.5V rail, there are 3x 6.3V 6800uF. So for now I'm going to rule out the capacitors as being the problem. No bulging or bloating anywhere on the caps.
There are even some surge arrestors on the input (spark gaps) as well as a very beefy line input filter.
Any help would be much appreciated...
After about a year of use, it developed a problem where it would reset itself randomly while in use. After a while it would keep cycling, seconds between resets.
The trace also tends to go to the maximum value when this happens too; I believe this is because the analog supplies were going out of tolerance.
Initially, I gave it a good clean and sprayed contact cleaner on the main connectors. That fixed it for about 2 years...
And now, it's doing the same thing... but cleaning hasn't fixed it...
So the question is what causes a supply to act like this? Why would it work fine for 2 years after cleaning it? What did the cleaning fix?
This is a very old supply. The scope was manufactured in 1993. The supply is capable of about 200W and is air cooled by a fan at the rear. (The fan also cools the rest of the instrument.)
It looks like a single power NPN forward with a very large transformer. Picture attached.
The supply is controlled entirely in discrete logic, as well as an LM339 comparator. There are no actual SMPS controller ICs anywhere on the board.
All caps are Chemicon or Rubycon.
This is a very nice power supply and an example of sheer overengineering. Look at the sheer number of capacitors on just one rail - 8 x 35V 1000uF (for the +15V supply, which runs the CRT and fan, and nothing much more.) On the +3.5V rail, there are 3x 6.3V 6800uF. So for now I'm going to rule out the capacitors as being the problem. No bulging or bloating anywhere on the caps.
There are even some surge arrestors on the input (spark gaps) as well as a very beefy line input filter.
Any help would be much appreciated...
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