notfred wrote:Thanks, that FJP5200 is substantially tougher, although it does drop the Ft significantly (30MHz instead of 125MHz), think I'll look for something a bit closer given this is an HF oscillator. It's put me in the right ball park though.
It's just a single NPN, I had drawn everything in xcircuit when I clicked the wrong button and lost it all Will redraw at some point, even if it's just a scan of a hand drawn schematic.
notfred wrote:I'm guessing C1 and C2 block the HF going out the inputs. The 16V AC is because that's the standard accessory power so that's why it's half-rectified rather than just running a DC supply.
jprampolla wrote:Hi Folks,
I just learned that the transformer used in the schematic I posted
"is a small bell transformer with a 230v primary and an 8 – 10 v secondary. Fitted 'wrong way around' it serves admirably as a step-up transformer. For North American applications you would need a 115v primary with a 4-5 v secondary, again installed the wrong way round.
jprampolla wrote:The principle is quite simple but effective, when larger DC current flows through the secondary winding it saturates the transformer to overwhelm the low current but high frequency AC."
So any suggestions as to an exact part number or source will be greatly appreciated!
jprampolla wrote:Many, many thanks for the reply and information!!!!!!!!!!!!!!!!!!!!!
After waiting actually many years, a few weeks delay isn't an issue. But, I am unclear as to the center connection on the left side of the transformer in the diagram and which side is low voltage. Looking over these transformer photos I have seen, I usually see only 2 connections on each side.
Thanks, Take care, Joe.
jprampolla wrote:Although I don't fully understand it, the motor's coils act as a choke to the HF AC.
just brew it! wrote:Rule of thumb: Inductors (coils) block high frequencies, capacitors block low frequencies and DC. The cutoff frequency (where the degree of blockage becomes significant) depends on the inductance or capacitance value, with higher values corresponding to lower frequencies.Another way of looking at it is that inductors tend to resist change in the amount of current flowing through them, while capacitors tend to resist change in the voltage across them.
jprampolla wrote:I was wondering if a 5 volt wall wart could be opened and that coil be used in the project, but opening that sealed case is almost impossible. I have a few that are screwed together, but most are glued/fused shut.
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