Old synth & variac, wasRe: FGTH, was Re: [sdiy] "Foot pedal"? !

[Tim Parkhurst]

Hey John,

Before I applied power to any piece of electronics that had been sitting
dormant for that long, I'd probably unhook the power supply and check the
resistance across the power supply pins at each board. You should get a
fairly low reading (probably less than 100 Ohms, perhaps as low as 15 or
20), but you should not read a dead short. This is just a rough check, but
it will at least expose any caps that have died and shorted out. After that,
I'd probably check the output of the power supply (with it still not hooked
up to anything). The only caveat there will be that a lot of switcher type
supplies won't start up properly without a load. My guess would be that a
twenty year old Jupiter won't have a switcher. 


Tim (forty-something and I don't have a switcher either) Servo

"Imagination is more important than knowledge." - Albert Einstein




> -----Original Message-----
> From: rkmoore at memphis.edu [mailto:rkmoore at memphis.edu]
> Sent: Monday, May 16, 2005 9:41 AM
> To: Paul Perry
> Cc: synth-diy at dropmix.xs4all.nl
> Subject: Re: Old synth & variac, wasRe: FGTH, was Re: [sdiy] "Foot
pedal"?!
> 
> Hi John,
> 
> I don't think I would run it up on a variac.  If it really hasn't been
> powered on in 20 years, I might disconnect everyhing from the power
> supply and power it up at no load first.  After checking for proper
> voltages and ripple I would power it down, connect everything again,
> and power on a second time.  This may not be the right techniques
> either, though.
> 
> Richard Moore
> 
> ----- Original Message -----
> From: "Paul Perry" <pfperry at melbpc.org.au>
> Date: Monday, May 16, 2005 10:30 am
> Subject: Old synth & variac, wasRe: FGTH, was Re: [sdiy] "Foot pedal"?!
> 
> >
> > ----- Original Message -----
> > From: "john mahoney"
> > > Should a keyboard that's been asleep for 2 decades be brought
> > back up with
> > a
> > > variac?
> > > --
> > I would think not, because the rectifiers & main caps are driving
> > regulators, and
> > the system as a whole isn't designed to run with an odd input.
> > In fact, with the input under-run, you will be sending odd unsmoothed
> > voltages to various parts,
> > with possible problems with analog and digital circuit interactions
> > (sometimes stuff is designed
> > in such a way that it needs some power rails to be always higher than
> > another, or to reach
> > operting voltage in a particular order).
> >
> > I hope that someone with more experience than I have will answer
> > as well,
> > but personally
> > I don't think it is ever a good idea to run anything outside its
> > designspecs, even on the low
> > side.
> >
> > paul perry (Frostwave analog fx) Melbourne Australia
> >
> >
> 
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