power supplies

[Goddard, Duncan]

I guess I should have made it clear that the gear I was referring to can be
switched to either 110 or 220 and naturally, being an engineer, I was using
the correct "export" setting of 220 when I made this observation. btw, it
was a sequential 2002 sampler that exhibited some misbehaviour until I
swapped out the mains transformer for a toroidal designed to work on u.k
volts.
78xx and 79xx are only good for their maximum va- if you are pulling a whole
amp through one, it will not satisfactorily shed excess of more than three
or four volts for very long. so if you intend running stuff off truck
batteries or something else that's a bit less predictable than house
current, the regs in big metal packages make more sense.

some sony video monitors will work (switched mode, obviously) anywhere
between 75 and 350 volts, though they get fried at the higher voltages;
anyone else out there sick to death of replacing the "racehorse" transistors
in smpsu's? they're very common in broadcast equipment aswell as computing,
yet only in the last four or five years have they begun to appear in synths
and samplers.... 

duncan.

> ----------
> From: 	Tony Allgood[SMTP:oakley at techrepairs.freeserve.co.uk]
> Sent: 	04 August 2000 19:41
> To: 	synth-diy at node12b53.a2000.nl
> Subject: 	Re: Digital Delay w/a mind of its own...
> 
> >... I've had american gear that was designed to run on 110 or 220
> get upset by 240 because the regulators (78xx etc) couldn't throw away
> enough of the volts coming out of the bridge; they overheat and shut
> down
> for a while.
> 
> 110V stuff should never be used in the UK at all without a step down
> (auto)transformer or a new transformer. You will have over twice the
> voltage being applied to the regulators if you don't, most 78/79xx will
> die permanently if you exceed 37V. The smoothing caps will go bang at
> some point as well.
> 
> Trade shows are a good for this. US one day, then Europe the next...
> whoops, someone forgot to change the little switch at the back and now
> our Spectrum Analyser doesn't work, and what's that smell?? :-)
> 
> However, there are units out there that will run on any supply from the
> lowest 95V in Japan to the highest here in the UK. Tend to be switch
> mode though.
> 
> Regards,
> 
> Tony Allgood  Penrith, Cumbria, England
> 
> Modular synth circuits, TB303 clone and Filter Rack
> www.techrepairs.freeserve.co.uk/projects.htm
> My music: www.mp3.com/taklamakan
> 
> 
> 
> 


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