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

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 ).

I'd strongly encourage you to ask around, find somebody who has one,
and do the power-up with the variable-voltage transformer. Take your
time - ease the voltage up from zerch to nominal over a period of a
few minutes.

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 ?

If you do this, do the former... low-wattage. You want to power up
the rig *slowly*, so that the dielectrics in the electrolytic
capacitors have a chance to re-form gently. The lower the wattage of
the bulb (the higher the resistance) the longer it'll take to charge
the power supply fully and the lower the final voltage will be.

You could do it in stages. Wire up a standard light-bulb socket in
series with a power cord for the rig. Start out with a 5-watt bulb,
power up, let the rig sit for a few minutes, power down again, switch
to a 25-watt bulb, repeat the process again... then go to a 100-watt
bulb, then a 200-watt bulb.

This approach isn't as effective, or as controllable, as using a
Variac or similar variable-voltage transformer. The bulb's resistance
will be low when it's cold, and will rise when it heats up... so it
won't limit the initial inrush current all that effectively.

Would this be as good as a simple L-C network ?
Somebody said just plug it in.

It might easily go BOOM if you do. If it's been sitting around
un-powered for 30 years, the dielectic oxide layer in the power supply
caps may have thinned and developed pinholes... hitting it with full
mains voltage and no current limiting could result in a sudden short
circuit inside the caps. They're quite spectacular when they blow...
messy, though.

Are there any other
ideas ?

Negative-temperature-coefficient resistor instead of a light bulb?
These are used as inrush suppressors in switching power supplies...
their initial resistance is high when they're cold, and drops when
they warm up.

Borrowing the use of a Variac for half an hour is still a better way
to do it, I think.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

On Aug 16, 4:03 pm, (Dave Platt) 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 ).


KISS. Wire a 60w light globe in series, turn it on, let it sit for a
few hours. Filaments OFF for this test.

Havent used a variac for this for years - reason - its the switch on
current surge thats going to kill old electros, and the variac has no
current limiting whereas the light bulb does. You will see a brief
"Flash" as the caps charge up, then maybe a dull glow, eventually, no
light at all.

Given that the caps used were / are modern, and of good quality to
start with, the KISS method works well.

Oh, BTW - when all this is done, apply full mains power, let the tube
filaments soak for a few hours lest they have gone gassy.

Andrew VK3BFA.

I tell you what Dave:

Save the grief and replace the caps.
What your'e doing is betting that
you can reform the electrolyte that
may be left in the capacitors after
30+ years.

I hope you win that bet.

73 OM

n8zu

Andrew VK3BFA wrote:
On Aug 16, 4:03 pm, (Dave Platt) 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 ).

KISS. Wire a 60w light globe in series, turn it on, let it sit for a
few hours. Filaments OFF for this test.

Havent used a variac for this for years - reason - its the switch on
current surge thats going to kill old electros, and the variac has no
current limiting whereas the light bulb does. You will see a brief
"Flash" as the caps charge up, then maybe a dull glow, eventually, no
light at all.
==============================================
Don't understand the above.
When using a variac starting at zero and gradually increasing the
voltage there can't be any appreciable inrush current.

I happen to have a 8 Amperes variac and would always use it to 'fire-up'
a previously retired oldtimer (boat anchor)

I have a rather large junk box with high capacitance value elcos and
recently exposed them all to a 'zero to max working voltage' from an
adjustable HV PSU. I do that once every 3 years.

Frank GM0CSZ / KN6WH

On Aug 17, 11:21 pm, Highland Ham
wrote:

==============================================
Don't understand the above.
When using a variac starting at zero and gradually increasing the
voltage there can't be any appreciable inrush current.

I happen to have a 8 Amperes variac and would always use it to 'fire-up'
a previously retired oldtimer (boat anchor)

I have a rather large junk box with high capacitance value elcos and
recently exposed them all to a 'zero to max working voltage' from an
adjustable HV PSU. I do that once every 3 years.

Frank GM0CSZ / KN6WH

Well, mine took out a few SMPS power supplies, and its a pain in the
arse to set up, connect meters, gingerly spend time slowly
incrementing the voltage - life is too short to stuff around......

Hey, you got time to do Rocket Science, thats fine. Each to his own.

Andrew VK3BFA.

On Aug 17, 6:44*pm, Andrew VK3BFA wrote:
and its a pain in the
arse to set up, connect meters, gingerly spend time slowly
incrementing the voltage - life is too short to stuff around......

Hey, you got time to do Rocket Science, thats fine. Each to his own.

I think that turning it on, blowing up the capacitors that are gonna
blow up, and then replacing the ones that actually did blow up is a
fine procedure, myself.

There is a certain pussyfoot attitude about either cranking up the
variac gingerly, or simply recapping the whole radio, that is not
really appropriate to somebody (me!) who really wants to see smoke
coming out at least once in a while.

Only gotcha, if the bad capacitor takes out a transformer, that's a
PITA. Not that I've never rewound bad transformers or rewound them for
a project, but having to rewind a transformer just because I was
impatient is a little embarassing.

Tim.

Andrew VK3BFA wrote:

On Aug 16, 4:03 pm, (Dave Platt) 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 ).


KISS. Wire a 60w light globe in series, turn it on, let it sit for a
few hours. Filaments OFF for this test.

Havent used a variac for this for years - reason - its the switch on
current surge thats going to kill old electros, and the variac has no
current limiting whereas the light bulb does. You will see a brief
"Flash" as the caps charge up, then maybe a dull glow, eventually, no
light at all.

Given that the caps used were / are modern, and of good quality to
start with, the KISS method works well.

Oh, BTW - when all this is done, apply full mains power, let the tube
filaments soak for a few hours lest they have gone gassy.

Andrew VK3BFA.
Well I still use a kenwood 820s and it goes fine. In fact I'm just
putting the WARC bands into it.
The only parts I would be really concerned about are the 450 vot
electros in series acroos the 800 volt final ht supply. If you were very
careful a good look at the caps smoothing the 300 volt screen and driver
plate supply might also be a good idea. If you do a search on google you
will find all the tech data you might need including circuits and manuals.
It's a pretty good rig except for some poor final tank design on some
bands. a rewind of the Pi network inductor can help a lot and the use of
the proper values for a working Q of 12.
This can give you up to 25 or 30 watts more output on some bands with no
more DC input. It also saves you finals a lot of potential grief. See
the QST 1983 upgrade article for a few ideas.
Cliff Wright ZL1BDA ex G3NIA

On Aug 18, 1:38 am, (Edmund H. Ramm) wrote:
In Andrew VK3BFA writes:


Are physics reversed down under? Up here in the old world a light
bulb's filament (tungsten) resistance increases with temperature.


Er - yes, thats correct.So whats the problem?

Andrew VK3BFA.

On Aug 20, 8:27 am, (Edmund H. Ramm) wrote:
In Andrew VK3BFA writes:


There will only be negligible inrush current limiting. For that you'll
need an NTC resistor like an Epcos NTC22. All you get from a light bulb
is a voltage reduction -mains voltage minus the voltage drop across the
bulb- but only AFTER the inrush current you intended to prevent has already
flown.

A light bulb in series with an inrush current limiter might be suitable
for smoke testing equipment after prolonged disuse, though.


Yes. Whats the DV/DT of the positor versus a light bulb? - I got no
idea.....
The light bulb method works - its quick and dirty, and so far I have
never blown an electrolytic capacitor using this method. Its also VERY
useful in firing up SMPS devices - it does current limit quick enough
if theres a gross fault to prevent damage.

But, each to his own. Of more concern would be corrosion /freezing of
pots/switches etc. And a 30 year old mains power cable? - mm - and
what about checking the insulation resistance of the power
transformer..

But it ain't the Space Shuttle - live dangerously...Just Do It....

Andrew VK3BFA.