Hi:
I joined this group on the 17th and asked for a daily digest, but none
have arrived, so have missed a few postings.
I repaired my synth many years ago by replacing the SRD with the
biggest slowest one I could find. But it has died again.
The problem is in getting a SRD with a lifetime that's long enough to
work with a 1 MHz input signal. Since diode lifetime goes up with
temperature, HP used a heater to increase the lifetime and thus get a
stronger set of combs out of the diode.
The idea is that during fordward conduction the diode stores charge
and when the input polarity reverses the diode keeps conducting
(because of the stored charge). When the stored charge is all removed
the diode "snaps" to the reverse voltage. In the ideal case the
stored charge runs out when the reverse voltage is at it's negative peak.
In this case that would take a huge amount of charge storage and so
it's a case of the more charge the higher the output.
If someone knows of a large long lifetime SRD (or it may be called a
fast PIN, or noise diode) that may be a good choice.
Have Fun,
Brooke Clarke, N6GCE
