Posted by: maczrool
Dead VFD? - 13/05/2004 20:54
We have a dead display here. Does anyone know where the 60 volts is generated on the VFD? Is it internal or some from something on the display board? It is missing from this particular display.
Stu
Posted by: tman
Re: Dead VFD? - 13/05/2004 21:16
From what I remember when I last had my display board out, it is generated by a SMPS on there. It was some Maxim chip was wired to step up 12V to around 60V.
Posted by: maczrool
Re: Dead VFD? - 13/05/2004 21:34
Well, there's a MAX770 on the board, but it seems to max out at 15 volts according to the datasheet.
(Edit, nevermind. Other voltages are possible as well. It's late!)
Stu
Posted by: maczrool
Re: Dead VFD? - 17/05/2004 20:54
What is there between the output of the MAX770 at the resistor divider and the 60 volt pins at the VFD? Anything? I'm getting 3 volts at the pins and 59.8 volts right at the divider R2. I know there is at least a 22 ohm resistor to one of the pins.
Stu
Posted by: maczrool
Re: Dead VFD? - 18/05/2004 19:30
It was an open 22 ohm resistor that killed the display. Something must have shorted to the common leads on the display and fried it.
We put a temporary through hole resistor across the old surface mount one and now it's working again!
Stu
Posted by: JBjorgen
Re: Dead VFD? - 19/05/2004 06:59
Congrats. Now there's just the memory upgrade empeg to fix.