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.
Tell us your experiences with Monkey-designed products. Send stories to Rob Spiegel for Made by Monkeys.