D-shell connector age?
ard at p850ug1.demon.co.uk
Fri Jan 5 13:12:38 CST 2007
> Very common here also (chassis live) till mid 1990's then changed to
> isolation via the flyback transformer, partial hot chassis till
Interesting. There were sets over here (made by a company called Salora,
I think) that had what was commanly known as the IPSALO circuit. That was
an acronym for 'Integrated Power Supply and Line Output' (Line Output
being what we call the Horizontal Output stage). IIRC, the horizontal
yoke was on the live side of the power supply, the vertical yoke (and in
fact the entire vertical deflection circuit) was on the isolated side. Hmmm..
> flyback transformer. Then SMPS for isolation. Some do double
> isolation via SMPS then flyback transformer.
Never seen that,
> Still, certain area of chassis (just a one board now) even on SMPS is
> Isolation transformer is a MUST when servicing any even brand new
> set. No buts or ifs.
And, indeed, for working on any SMPSU (which are common in classic
computers, and therefore on-topic).
I think I've mentioend the origianl Tandy Model 1 monitor before, but
it's worth doing so again. it was based (as is well-known) on an RCA
protable TV, the tuner and IF boards were removed and the latter replaced
by a composite video input board. That TV was live chassis. US versions
have a on opto-isolater on the video input board (that's the reason for
the 5V power output on the model 1's video DIN socket, to power the input
side of the opto-isolator circuit), every thing else inide the monitor is
live!. European models have a step-down _isolating_ transformer inside
the case (since the TV chassis was designed for 115V mains input only),
the video input board is then little more than a transistor buffer stage.
Of course with that version almost all the circuitry inside the monitor
is isolated from the power line.
But be _very_ careful if you work on the US version!
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