3 Feb
2026
3 Feb
'26
2:25 p.m.
On Tue, Feb 3, 2026 at 11:55 AM Rob Jarratt via cctalk
<cctalk(a)classiccmp.org> wrote:
Actually a seller I have bought from before has some 2SB411s available. They aren’t cheap
but I don’t mind, would it make sense to get a couple of these?
The transistors in a horizontal output stage have to handle high peak
voltages and are often run under conditions not really covered by the
data sheet. For this reason, apparent equivalents may well not work
(they will fail at switch-on).
I would always fit the original type if I could.
Be warned that other component failures can lead to the demise of the
horizontal output transistor. Capacitors open or shorted, for example.
Or shorted turns in the flyback transformer. A 'ringing test' is well
worth doing if you have the equipment to do it (basically a 'scope and
a fairly simple test circuit, there have been several publised in the
UK magazine 'Television' over the years.
-tony