Middle - Replacing the old transistors with other types. You can't see them, they are buried under copper.
Replacing in such a way is the fastest prototyping, here a small PCB
would be of course a better solution, but this is a later step.
|Top Trace||5V/DIV||Load DAC||Oscilloscope triggers on first division|
|Center Trace||2V/DIV||DAC Output||0V to +10V full scale step|
|Bottom Trace||20mV/DIV||Gated Settling Time Waveform||20mV/DIV = 500µV/DIV|
|Test Equipment - 7A26 amplifier in 20 MHz position|
|No Oscilloscope Overdrive|
|Left photo with yellow arrow, (DAC has already settled), after swithing
ON the Sampling-Window, there is a small 200ns error on the rising
slope. Right photo (red) increased settling error and higher
Such a small piece of copper on the wrong place disturbes the circuit.
It's a funny job to solder a piece of copper on such small pads with a patch of 0.15mm. For
soldering you should glue the transistor first on the board and
then use pre-soldered very thin single copper wires and a
microscope magnification of approximately x20.
Up to now circuit don't work, starts to oscillate and shows funny curves. I did a check on the curve tracer of these self-made diode bridge.
Unfortunatel< this transitor don't work like a normal small signal
diode, in reverse connection the current breaks trough very fast. This
is the reason why this diode bridge didn't work in the circuit.