On Mon, 5 Dec 2011 17:41:19 -0800 (PST)
Michael Hawkins <
korgpolyex800@...> wrote:
> Gordon,
>
> I beg to differ on this point, though I hesitate and exercise a hefty load of humility before doing so.
No no, you've worked on these instruments a lot more than I have, so you should know ;-)
> But the problem with your thesis is that no power supply should ever be considered without the load, even despite the proliferation of modern regulated power supplies.
Right, but the Poly 800 isn't drawing 1A all the time and the average draw is somewhat closer to 800mA.
Get a 12V power supply and run your Poly 800 off it with a 1 ohm resistor in series and stick your 'scope across said resistor - look at the current, it's all over the place! At least, it is on mine...
> And so, if a Poly owner does connect a 12V DC supply that is rated to 1Amp or higher and is (even worse) a regulated supply, then the additional 3 watts of power must be dissipated by the Poly 800 power regulator. Unfortunately, the design of the Poly power supply does not dissipate the additional 3 watts very well at all.
>
> Those little BD transistors end up cooked - badly burned actually! Destroyed, busted, kaput!
I have to say, even at a nominal 12V input I haven't noticed the regulator trannies get even particularly warm. The standard Korg PSU I have puts out just shy of 11V on load, so one would assume that if the factory PSU does that then the Poly 800 is designed to cope with it.
I can't see that an additional 3W dissipation would zorch the regulator trannies to that extent, but persistently connecting up a high-current PSU ∗would∗ - after it had blown the legs off the protection diode. I run across this at work quite frequently, with one customer in particular who seems to delight in connecting their radio across the car battery backwards, blowing the fuse, replacing the fuse with a higher rated one, and continuing the process until the radio leaks its magic smoke. It then makes its way to me for a new protection diode, a new RF power amp and a new audio power amp. The worrying thing is that this is the workshop of one of the "blue light services" ;-)
--
Gordon JC Pearce MM0YEQ <
gordonjcp@...>