Yes, indeed Jim. To be perfectly honest, in the finished article, that was an over-sight omission. It did feature in the earlier development designs: a 12-v. Zener. Fortunately, it is easy to fit, retrospectively.
And thank you for pointing it out to me.
I'll also take this opportunity to mention (for the benefit of anyone who builds this PSU) that the values of the fixed resistors on each 'side' of the 100 kΩ Vout pot. are very much a 'select-on-test' affair. It will be wise to aim at values in the region of those stated and to avoid large changes, + / -, from those values. The reason for such a 'S-O-T' procedure is primarily because of the wide range of hFE in the 2N3439 and the corresponding variation on the IRF340; secondly on account of the tolerance spread of the various resistor values.
Al.
And thank you for pointing it out to me.
I'll also take this opportunity to mention (for the benefit of anyone who builds this PSU) that the values of the fixed resistors on each 'side' of the 100 kΩ Vout pot. are very much a 'select-on-test' affair. It will be wise to aim at values in the region of those stated and to avoid large changes, + / -, from those values. The reason for such a 'S-O-T' procedure is primarily because of the wide range of hFE in the 2N3439 and the corresponding variation on the IRF340; secondly on account of the tolerance spread of the various resistor values.
Al.
