Vu-Data PS941B viewing probe compensation calibration output (in the back!)
The
VU-DATA
Corporation PS941B oscilloscope is a fairly basic
4 inch rectangular face, electrostically deflected, shielded CRT
Graticule is a thin transparent sheet in front of the CRT
2 channel, estimate 20MHz bandwidth oscilloscope.
Year: Estimated 1976
Time/division: 500ms to 100ns (pull red knob to divide by 2 in 50ms/div or
faster sweeps; turn red knob all the way clockwise to match graticule)
Input volts/division: 20V to 10mV, AC/DC/GND coupling. Adjustable gain (as
with most scopes, turn red knobs all the way clockwise to match graticule)
Add/subtract (with inversion of channel 2); Chop/Alt/single channel display
Adjustable trigger level with AC/DC/HPF/LPF/auto coupling, ± slope,
external trigger
Calibration output on back (fixed frequency)
12VDC (2 pins) and 120VAC (standard IEC60320 C14) power inputs,
with battery charger mode to charge lead acid batteries. Yes, the power
supply will run off a car battery if needed.
The internal guts of the scope is very similar to what you'd expect from a scope from the era. Many op amps (TO-5 cans) and transistors (TO-92 plastic) fill the design. A few TO-220s for the PSU are around. I noticed mine had only a few electrolytic capacitors; most of the capacitors in the unit are tantalum. It even has the typical delay line which I only recently figured out what it was for as my Tektronix 2465 had an issue where I had to inspect it. The only thing that's a bit strange is that this oscilloscope is "modular" and seems that the sweep, power, CRT, and Y axis amplifiers are distinctly separate from each other and connected together by gold plated quick disconnect contacts. No ribbon cables.
As this is a fairly basic oscilloscope, there is NO XY mode and NO Z axis.
However there is external triggerring.
I don't exactly know what the bandwidth of this scope is and thus estimate to
20MHz by the sweep speed.
I will need to get a fast rise time jig to see what
the real bandwidth is and compare it to my Tek. I built an avalanche
pulser on a breadboard and used a chinese clone P6100 probe. I measured with
guesstimation (as there's no cursors and counting fractions of a division is
not an exact science) a risetime of around 20ns. This is about the 17.5MHz
using Tektronix's formula. It could very well be the rise time is 17ns due
to measurement inaccuracy, which would put the bandwidth at the 20MHz mark.
Apparently there are several versions of the PS94X series from the PS940, PS941, PS942, and PS943. From what I can deduce from random sources, they may have slightly different bandwidths or different power configurations. The PS940 is clearly rated as 20MHz and weighs 9.5 pounds.
The only price I could find is that there was an ad for this scope for a mere 395£ in 1981 in the United Kingdom. I have not seen a USD reference yet.
This scope has seen its use. I was able to debug multiple things with it, including my Fisher tuner/amp, Sony Handycam, and my (get this...) Tektronix 2465 oscilloscope with it. It has served well, and will keep on going. Now finding a service manual for it will be tough, but hope it will never be needed. Mine's missing the four back feet, one of the bottom feet, and I don't have good probes for it - the one that I do have is broken.