On Aug 22, 5:06 am, " wrote:
On Aug 16, 1:04 am, wrote:

Now retired I'm trying to become active again.
My TS-520S has not been on for 30 years.
I don't have a variactor ( variable transformer ).
At the TARC advice was to put a lightbulb in series
to take the surge. Should I use a high resistance
( low wattage ) bulb or vice versa ?
Would this be as good as a simple L-C network ?
Somebody said just plug it in. Are there any other
ideas ?
Thanks for your kind assistance.
Dave WB3DWE Temple, TX

A couple of disclaimers first:

a) I know diddly/squat about Ham equipment. I am not a Ham.
b) I have been noodling about with vintage equipment, tube & solid-
state for now over 30 years, so I am familiar with the species. What I
write below is a generic approach to (re)starting vintage equipment
after some years at idle.

So:

As I understand, the Kenwood is a tube-based unit, however it has a
solid-state rectifier and is mostly solid-state in general. What this
means is that there is some validity to bringing up the voltage slowly
using a Variac as the caps will see a gradually increasing voltage -
unlike what they would see from a tube rectifier which does not pass
current until about 70V or so.

That it is from the transistor era, at least in part, suggests that
the filter caps may be of sufficiently recent manufacture as to be
likely to be good - the operative word here is *LIKELY*, not
*certainly*. Kenwood was also not know to use cheap-junk caps in their
equipment.

HOWEVER: A variac is really no better than a dim-bulb tester unless it
is equipped with a current meter (amps or watts) that will read the
actual current draw of the unit. I have been known to RANT on this
subject at length - but I will spare this group and merely state that
UNLESS you have the means to measure actual current drawn by the unit
and at a sufficiently fine degree as to give you useful data, don't
waste your time with a Variac. It gives you a false sense of
security.

IF you have the means to measure current - either with your VOM in
series or with a poor-man's ammeter (measure voltage drop across a 1-
ohm resistor, for example), this technique is very useful. Raise the
voltage s-l-o-w-l-y, watching the meter all the time. It will jump up
(typically) then slide down as the caps charge. Slowly-slowly-nicely-
nicely until you reach operating voltage over 4-5 minutes or so. And
KEEP WATCHING!

If the caps start to fail at full B+, you will see that meter creep
up. If they go anything beyond about 80% (SWAG guess - more below) of
the nameplate rating of the unit, you have real problems.

Now, here is where I cannot comment beyond the generic - I have no
idea what the quiescent vs. active current draw is with the Kenwood.
THIS IS IMPORTANT. As you will not be transmitting or whatever, you
should be operating at/near the quiescent current. This may be a very
small percentage of the full nameplate rating - my guess is that this
is so. You will need to know what that is. If you are operating even
5% beyond the "proper" quiescent current, that will be expressed as
heat somewhere - and eventually *POOF* at some unobtanium or expensive
part.

You get the point. The idea is to bring power to the beast slowly so
that failed caps or similar may be discovered before any actual damage
is done. For this to work you need a means to determine whether the
unit is taking excess current - and you need to be able to measure
this in fine-enough increments to be worthwhile. Otherwise, you are
wasting your time as a small problem or series of small problems will
be invisible to crude means.

I keep this unit for these sorts of tests:

http://www.oaktreeent.com/web_photos...P-5220_web.jpg

It is an metered Iso-Variac, overkill for once-in-a-while needs, but I
use it constantly.

Peter Wieck
Melrose Park, PA

Peter - lots of good stuff in there, but perhaps overkill..like the ac
power supply with its own meters - would be simple to use for the
methods you describe.

The Kenwood is a "Valve hybrid" - there are 3 tubes in there, a driver
and 2 output tubes in //. Filamnets are switchable on/off. Idle
current is.....very low, never measured it, had no need to. The light
bulb method does work sufficiently well for the purpose intended.

Andrew VK3BFA.