Kennedy 9800 - Power-up tips?

Jon Elson elson at
Thu Apr 23 13:09:53 CDT 2020

On 04/23/2020 12:53 PM, Robert via cctalk wrote:
> I'm under caffeinated and not really with it yet, having recently gone semi
> nocturnal, so you'll want to double check this with someone who's actually
> awake.
> That said, variacs aren't a universal panacea and can sometimes be harmful
> rather than helpful.  My disorganized memory is offering TVs as an example,
> 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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