OB-8 power supply, and problems starting

[Tony Allgood]

Hi Juergen and all,

>Would adding "backward" diodes across the regulators, and reverse
diodes
on each regulator output (to short a possible voltage inversion) be safe
enough,
or is a crowbar circuit (thyristor etc.) across the CEM supply voltages
recommended, too ?


The reverse and backward diodes are always a good idea, although I do
remember reading that one is not necessary across the negative 79XX
since the substrate actually behaves as a diode. I have never put this
into practice though. The CEM supply is an interesting one. I am not
familiar with the OB-8, but the Elektor article on the CEM3340 did
recommend using a 11V rail rather than the usual +15V. This reduced
power dissipation in the ic and kept it in tune better. It goes without
saying that the negative rail should be a well regulated -5V. I suppose
you could add an 11V regulator to the 15V rail, theres enough headroom
to keep even a 723 ic happy, and it would certainly protect your
CEM3340s.

Regards,

Tony Allgood, Cumbria, UK

Rack mounted moog filter and the TB3030 SuperBassline projects:

http://aupe.phys.andrews.edu/diy_archive/schematics/oakley/