PaulApr 14
2/ One of the curiosities on the prototype of this #tektronix plug-in is the elapsed time meter on the bottom. It is not present on the production unit. There is a note that I cannot decipher with a date or February 16 1966.
This type of indicator is a Mercury Coulometer, and shows time elapsed using a chemical reaction which moves a drop of mercury in a capillary tube slowly and linearly as chemical reaction is caused by the passage of a small, fixed current.
This unit has a large number of reed relays, which have a finite lifespan, and I wonder if this meter was there to measure usage during testing.
Show threadPaulApr 14
3/ the prototype unit also has factory modifications that seem to correlate to a later rev of the board on the production unit.
Show threadPaulApr 14
4/ The prototype unit didn’t work when I first tried it. No real troubleshooting was done
The newer unit had a resistor near the back of the unit that was hanging on by only one lead. This was R563, a 10k 8W, 1% precision resistor off the anode of a tube in the output section.
Funny enough, it wasn’t until I put the units side by side that I realized this resistor was also missing from my prototype unit. It’s kind of a flat, wide, rubberized package that’s near the plug-in connector and is prone to damage.
So that’s a smoking gun as to why my prototype unit doesn’t work.
Now to find a suitable replacement.
Show threadPaulApr 15
5/ I use brass polish to clean a lot of faceplates, mostly because I once lived in an apartment with all brass door hardware, still have the polish, and one day decided to give it a go.
I’m sure there’s a better thing to use, and someone may tell me why using it is a terrible terrible thing, but it’s doing a heck of a job getting decades of cigarette smoke off the face of this thing, even on translucent plastic.
#tektronix #electronics #vintageTech #retroTech
Show threadPaul
6/ I replaced the 10k resistor in both. The prototype triggers but doesn’t display, while the crusty one displays but won’t trigger.
Going to try working on the non-gross one first; I’m hoping it’s something on the output amplifier.
Apr 17 at 11:56pmWeb
Show threadPaul2d ago
7/ It was the nuvistor. It’s always the f$&king nuvistor. Both autoranging plug-ins are somewhat working.
Vertical plug-in still has some ranging issues, and the horizontal plug-in is slow to un-blank, which becomes a problem at higher sweep speeds. I’ll tackle that next.
#retroTech #vintageTech #tektronix #1960s #testEquipment #electronics
Show threadPaul2d ago
8/ video showing what may have been the worlds first auto-ranging oscilloscope in action.
#electronics #tektronix #retroTech #vintageTech #1960s
Show threadPaul2d ago
9/ very confident that it’s a blanking issue with the plug-in - tried it with another horizontal plug-in just to make sure it wasn’t the mainframe.
A few other interesting features of the 3B5:
The delayed magnification feature. Instead of a separate timebase & intensification zone, it has a selectable 10x & 100x magnification, and the delay control changes the point at which the sweep goes into the magnified rate, so you can still accurately zoom into a specific portion of the waveform. I think this is how some of the later 400 series scopes did it. I like it.
The sweep speed goes up to 10nS / division which is the fastest of any of the 560 series plug-ins. Note while it’s labeled 10nS on the silkscreen, the illuminated indicator uses ‘mili micro seconds (m u S)’ to avoid adding a 3rd prefix.
#tektronix #electronics #retroTech #vintageTech #1960s #testEquipment
Show threadChuck2d ago
@forty2 Oh that is neat!
Show threadJill Veldhuis 💾2d ago
@forty2 Oh god, that's a sexy beast 🥵
Show threadRob Norris2d ago
@forty2 That is a treasure. Great work!