Hi,
Here is an overview of a curve tracer I built recently, don't know if this is of any help:
It all started when I was wondering what to do with this old oscilloscope that a friend gave me some years ago. I already had an analogue scope, and I was thinking of giving this one away to some deserving newbie, but it was in pretty poor shape: noisy switches, timebase not working, and I had already needed to make a repair to the EHT supply using the tripler out of an old TV set. So I decided, rather than burden someone else with it, I would convert it into a dedicated curve tracer.
To provide the drive signal, I used an amplifier out of some old PA equipment. This circuit used a couple of quasi-complementary 2N3055s, and was good for about 40W into 8 ohms. Conveniently, I managed to find some suitable +/- 35V supply rails inside the scope to power it. Maximum output swing is about +/-33V.
For the oscillator, I got lazy, and ordered a sine/square/triangle signal generator module from ebay, for the grand sum of $3.50. This feeds a front panel attenuator (I repurposed some of the controls in the timebase module), and some switchable level shifting to provide positive, negative, or AC output. I also added an adjustable current limiting circuit to the amplifier. (Let me know if you would like details).
The output of the amplifier is connected to the CH1/X input, which then becomes the drive output. The CH2 input has a 1 ohm resistor connected across it, to act as a current shunt. The input attenuators work as normal, with the CH2 one being recalibrated in amps instead of volts.
I also added a base drive staircase generator, based on the Elektor December 1989 circuit. (I think someone may have posted this on the forum somewhere - search around)
In the picture, the original X deflection board is at the back, then comes the amplifier module. The function generator is at the top, with the staircase generator below it. The current limiter is partially hidden behind the heatsink.
Edit 21/11/2018: spelling