Osborne Vixen - Zenith 7" display t-shooting issues

tony duell ard at p850ug1.demon.co.uk
Fri Nov 7 14:41:11 CST 2014

> Well, Tony may have a problem with this one, but SMPSU transistors and
> HOTs do share a lot of common characterists.  For example, instead of
> the NTE unit, consider the MJE13007, a old Motorola design that saw use
> in both SMPSUs as well as HOTs.  Common as dirt.

I believe I said many messages ago that the horizontal output stage is a specialised
SMPSU. It has been since the 1950s (yes, the 'line output valves' that I remember --
things like PL36, PL81, PL504, PL509, etc -- are choppers).

In the UK the BU208 (metal TO3 package) turned up in countless horizontal output
stages and SMPSUs.

BUT... My experience is that some horizontal output stages (and some more conventional
SMPSUs) can be remarkably fickle about what transistors will work there. And since the OP
is having odd problems, I would want to reduce the number of variables. If it doesn't work
with an MJE13007, then what? Is it that this transistor is not suitable, or is there some other


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