Kennedy 9800 - Power-up tips?
anders.k.nelson at gmail.com
Thu Apr 23 19:43:38 CDT 2020
Hey this is all super useful info, thanks!
Any idea how to visually identify a tantalum cap? I suppose I could Google
it but maybe standards have changed between 1984 and 2020?
On Thu, Apr 23, 2020, 8:06 PM Jon Elson via cctalk <cctalk at classiccmp.org>
> On 04/23/2020 12:53 PM, Robert via cctalk wrote:
> > I'm under caffeinated and not really with it yet, having recently gone
> > nocturnal, so you'll want to double check this with someone who's
> > awake.
> > That said, variacs aren't a universal panacea and can sometimes be
> > rather than helpful. My disorganized memory is offering TVs as an
> > but take that with a pinch of salt. I've only ever used them with tube
> > radios and amps, so have nothing further to offer, save this caution.
> Well, if the power supply is all linear, a Variac is
> probably fine to slowly ramp up the capacitors and
> let the dielectric reform.
> If it has switching power supplies, this can cause the
> supply to try to operate at severe undervoltage, and cause
> damage. On the other hand, powering it up to 10 V or so on
> the AC input for a few minutes
> is unlikely to allow the switching stage to start up, but
> will reform the main input storage caps.
> It won't reform the low voltage caps in the rest of the
> unit, though. You could apply low voltage
> (1-2 V for a minute or two) to each low voltage rail before
> fully powering on. Especially if it
> has bunches of tantalum caps in the logic, that could
> prevent disaster.
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