14 Aug
2014
14 Aug
'14
4:14 p.m.
Ok I think I see what's up. The FB primary isn't driven from line-derived
AC - it's driven by 125V DC, modulated by TS467, and I'm guessing at a
frequency equal to or some multiple of the horizontal scan frequency? Did I
get that right?
It's the horizontal scan rate. I mentioend in anotehr psot the reaso nfor
all this...
See and I always thought that the HV just provided a simple DC bias,
because that's the case in oscilloscopes - which are about the only 'video'
hardware I have any experience with.
It does. There HV spike from the flyback trnasofrmer is rectified (often
therectifier is uncapsulated inside the flyback transformer [1]) and
smoothed (the cpacitor may well be internal and external conducive
aquadag coatingson the CRT flare). the CRT runs at DC.
[1] wWIth colour CRTs a voltage multiplier circuit is not uncommon.
There is noreaso nat all why the CRT anode votlage could not be provided
my a mains-frequency [2] trnasofmrer, rectifier and smoothing capacitor.
The problem was that hthe mains trnaformerwas large and heavy, the supply
was downright lethal, and thatenergy was wasted in the horizotnal output
stage during flyback that might waswell be put to use.
[2] The term 'line frequency' is one that has differnet meanings on the 2
sides fo the Pond. To you it means the frequency of the power line
(mains). To me it means the horizontal scan requency (the horizontal
cirucit is the 'lien circuit'becuase it produces the scan lines.
OK, what about using an HV windign on an SMPSU trnaformer to produce the
HV? It's been done.One manufacturer, I forget who (Sabs?) had soemthing
they called hte 'IPSALO' circuit. It stood fro 'Integrated Power Supply
And Line Output'. The chopper trnansformer was the flyback trannsformer.
It was powered from rectifiend mailsm the chopper ran at hteh orizotnal
can frequency and was synchronised to it. The PSU choopy transofer had
the HV widnigns, drove the dlefieciton coils, etc.
-tony