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Re: FBSSTC-NEED HELP



Original poster: Fucian-at-aol-dot-com 

BREAKTHROUGH!!!!!!!!!!!!!!

Today i decided that something had to be worng...SO i isolated the 4420 to 
test if it was even working at all...I applied 12 volts to pin 2 and viola, 
got 12 volts out of its output!That means that IT is working just fine!

SO i decided that something is up with the 555...Since i WAS getting 12 
volts out of it, i thought it may have to do with a WEAK signal to the 
4420...Since the 2 10kohm and capacitor  were desgined to weaken the 
signal, i guessed that it might be too weak. I hooked the 555 right up to 
the 4420...Got 12 volts out of the 4420 when i touched the antenna 
wire!Bingo!Seems the 555 is messed up fro some reason...It outputs 12 
volts, but doesnt output a frequency?Seems its just continous now...

SO i yanked the 555 right off the baord and hooked the 4420 up to  a single 
irfp460 and an old OLD tesla coil...Turned on power...Touched the antenna 
and got some output!It was about 1.5mm lol yes millimeters...Was about 20 
volts dc in to it...weird...But it was WORKING...

So now i haqve decided to use JUST the 4420 and try to add a 4429 and a GDT 
for half-bridge operation...I did connect a variac in to raise the 
voltage...The output was still 1.5mm, but a lil more ferocious...Why is 
that?It was getting like 50volts?Probably cuz the leads to the MOSFET were 
22 awg hook up wire and several inches???WOuld that mess it up??The variac 
was buzzing, sounded like it was saturating...Its only a 4.5amp one, so i 
will hook up the 9amp one later...

Heres what i want to do now. I want to use the 4420 and another 4429 to 
drive the GDT via a bypass capacitor. The GDT will then power the 
half-bridge...

Can i do this?What else do i need. I want this to be super simple...I know 
doign the 913 +74ls14+4420/4429 deal is better, but thats alot of ICs+ 
Regulators and mess...I want somethign simple...

Another Q-even though the oyutput sucks, it seems to start w/o me touching 
the ant. why is that?I thought it HAD to have something to get it going?Or 
ok nvm...The 4420 turns on the MOSFET and pulses the primary...gotcha....

Matt