7A16A high frequency compensation.


unclebanjoman
 

Hi all,

I've recently purchased a 7A16A, working, looks new, S/N B138015.

Probably the previous owner has tried to calibrate the HF response in a badly manner: risetime was 3 ns with very rounded front corners.
Suspecting a strong misadjustment of HF compensation, I did a full calibration procedure.

Problem: I'm unable to obtain a decent compromise between risetime and flat-top and square corner.

I'm using a PG506, a Type 111 and 7854 mainframe. 7A16A in the left compartment, no extender.

Following the procedure as per manual, I spent 4 hours trying to calibrate the best, but the various settings interacts with each other and I'm unable to obtain a decent rising edge.
Sometimes the rising edge is distorted in the middle of the front. Other time there is an auto-oscillation. Touch one trim and the waveform gets better. I touch another one and the waveform gets worse.
I heard that the calibration procedure was tricky, but I have never encountered a difficulty like that.
All resistive and capacitive trimmers are O.K, perfectly functional.

Does anyone know a better procedure than the (fairly simplistic) one outlined in the manual?
Moreover, in the manual there is not even a photograph of some typical waveform that can be used as a reference. Does anyone know where to find a screenshot of a typical 7A16A step response?

Cheers,
Max

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