My first solid state scope was a Tektronix 2245A, which I carried around proudly, knowing that 100 MHz would be adequate -- well, for a few years, anyway. This scope worked well. I used it to debug lots of audio, microcontrollers, and other projects. At one point, my manager at the time said: “We need another scope for six months.” I told him about mine and he said: "Bring it down." I did and received a Wavetek LCR meter as rental fee.
A few years after I bought it, I went to power my scope up, but there was no sweep. I was in despair. When your lab is only one scope, one meter, and one homebrew function generator and power supply, the scope is stage center. After playing with the controls, I discovered I could get a sweep if I put the time/division optical encoder in between detents. So I knew the high voltage, vertical and horizontal amps, and sweep, were OK.
I decided to open up my scope. I had an idea that maybe something was wrong with the front panel. I laid the front panel down in front of the scope, with cables still connected. I had a service manual so I looked at the rows and columns of the keyboard scan. One of the signals was goofy. I narrowed it down only to find a green LED that signified AC coupling on Channel 1 was shorted. This is the only LED I have ever seen with this fault -- except the ones I purposely ran at 200 mA just to see how bright they got.
Since I had to install a new LED, I decided my scope would now use two red LEDs to signify AC coupling. To this day, it works quite well, and has no other issues. But, it's relegated to a back wall bench, usurped by ever faster scopes, some 23 at last count.
This entry was submitted by Steve Lindberg and edited by Rob Spiegel.
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