The Phillies are playing in the grapefruit league, and summer is on the way! In honor of that, here's a nice Shakespearean rendition of 'Who's On First?', one of history's best comedy stand-up routines...
An experimenter in a facebook group that I'm a member of put up the following schematic. They asked for group members' help to give a simple explanation of the circuit. I've put the schematic here, so that I can give some feedback with a little space and some links.
The above circuit is a fluid level meter that converts the level in the container on the left into a single-digit number, from 0-9 on a seven-segment display. In this case, 0 (zero) represents the lowest level, and 9 (nine) is the highest level.
Finally got the intensity problem fixed on the new (used) scope. It was a couple of bad diodes and some supporting components. I tried to get the originals, but that was not going to happen in any decent time frame.
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Trusty ol' 1N4004 diodes don't have the fancy low-capacitance, high-switching-speed of the original diodes, but they have more than enough reverse voltage and power handling. . . Hmmm. . . would they work? YES! The scope is all calibrated now, and works like a charm. Now that the brightness works I can see what the whole Inten'D thing is for (my old Heathkit scope didn't have delayed triggering). Pretty cool!
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Summary: $80 + a little elbow grease = 35 MHz Dual Trace Scope
The $80 price includes the shipping cost!
Model: JDR Instruments 3500
Found and downloaded a free manual (images scanned into a PDF). It was needed for the schematics to fix the intensity problem, but it also included the calibration procedures.
The guy who sold it was a bit of a sleaze bag (imo). He said, directly, that he wasn't aware of any problems, though he took a picture of it with the traces showing pulses. To me, that means he would have fiddled with the focus and intensity controls and seen that the intensity control had no effect.
So, it had a problem with the intensity that turned out to be two different diodes in the intensity circuit (go figure).
Now I've got a scope that probably cost >$1K new, and would cost $200-500 used in good working condition today. Not too shabby.
It came in the mail yesterday. A used, JDR Instruments, 35 MHz, dual trace scope for $80.00 (Shipping included) on eBay!
It had two obvious problems.
No horizontal positioning — I was able to fix that by following wires and traces back from the front panel.
The brightness is at full all the time — not able to fix that without schematics.
I spent a bit of time with it, and while it needs some calibration, I haven't been able to find anything else wrong. Also cool, it has a Z input in the back, which means I'll be able to play asteroids on it
The instructions on the box call for three eggs and that's what the first try used. It seemed just a little bit too cakey and dry to me.
Reducing the amount of egg made it just a bit richer and moister, but not crazy-rich. Of course, I'm using jumbo sized eggs, which may make a difference. If you're using smaller sized eggs, three is probably going to be fine. whip them thoroughly first in the measuring cup before adding them into the mixing bowl with everything else.
Finally managed to slosh enough junk around to clear the table in the foreground and then clean off the old workbench. The last time it was out from under a quarter inch of dust you needed a t-square to produce PCB layouts (see it there). The old scope smoked out as soon as I turned it on. It smelled up the whole basement.
All the bread-boarding sockets had been left completely uncovered under all the dust and in the dampness for the entire time. Nonetheless, I decided to assemble a small, experimental, logic circuit on the old breadboards and surprisingly, the circuit worked!
So, what does it mean if, while other guys are spending time and money building man-caves, you start building a maker cave? Well, you might just be a geek my friend.