09-11-2019, 12:54 PM
It's not complicated. All that's needed is connections to the ends of the rotary switches for the heater and screen. The Tektronix can do the grid (to -19) and Anode. Add a 4 pole change over switch and a socket beside the rotary switches. I'm using a 7 or 8 (forget which) way connector of the style used on CB and Ham rigs.
Perhaps some of the Tektronix testers don't do Depletion mode N JFETS, like my friend's tester that has 0 to -19V for gate and over 1300V for drain.
No amp needed. Also unless the Tektronix is doing the control grid and Anode (or screen, you can swap) it's not a full curve tracer.
Admittedly some valves do need less than -19.
There is an issue that the screen voltage needs smoothed and regulated as it's half wave pulses.
I've downloaded the manual / blurb and the only thing in it that's needed (for only a few valves) is the amplifier:
"Semiconductor curve tracers do not have voltage steps large enough to drive a low-mu triode from full
conduction to cutoff. The VTCT adapter includes a Grid Voltage Step Amplifier that has gains of X1,
X10 and X100 and an output range of +5VDC to -50VDC for this purpose."
Except the Tracer in question set up for N JFETS seems adequate.
I guess the design is to accommodate inferior Tektronix curve tracers and inferior valve testers.
Valves should be fully tested for shorts & leakage, cold and hot, then tested normally for Ia and gm before curve tracing. The Curve tracing is pointless for restoring gear and the best test of valves (quoting Tektronix) is in the intended equipment, after verifying it has the correct voltages etc.
Valve testers were needed in factories or wholesale for QA, or big service depts. They aren't actually needed by a restorer of a radio or amp.
The curve tracing is really only of use for designers or the curious.
Perhaps some of the Tektronix testers don't do Depletion mode N JFETS, like my friend's tester that has 0 to -19V for gate and over 1300V for drain.
No amp needed. Also unless the Tektronix is doing the control grid and Anode (or screen, you can swap) it's not a full curve tracer.
Admittedly some valves do need less than -19.
There is an issue that the screen voltage needs smoothed and regulated as it's half wave pulses.
I've downloaded the manual / blurb and the only thing in it that's needed (for only a few valves) is the amplifier:
"Semiconductor curve tracers do not have voltage steps large enough to drive a low-mu triode from full
conduction to cutoff. The VTCT adapter includes a Grid Voltage Step Amplifier that has gains of X1,
X10 and X100 and an output range of +5VDC to -50VDC for this purpose."
Except the Tracer in question set up for N JFETS seems adequate.
I guess the design is to accommodate inferior Tektronix curve tracers and inferior valve testers.
Valves should be fully tested for shorts & leakage, cold and hot, then tested normally for Ia and gm before curve tracing. The Curve tracing is pointless for restoring gear and the best test of valves (quoting Tektronix) is in the intended equipment, after verifying it has the correct voltages etc.
Valve testers were needed in factories or wholesale for QA, or big service depts. They aren't actually needed by a restorer of a radio or amp.
The curve tracing is really only of use for designers or the curious.
