[Boatanchors] restored radio question

[jeremy-ca]

----- Original Message ----- 
From: "J Forster" <jfor at quik.com>
To: "jeremy-ca" <km1h at jeremy.mv.com>
Cc: "Gerry Steffens" <gsteffens at pitel.net>; <Boatanchors at mailman.qth.net>
Sent: Wednesday, October 10, 2007 10:10 AM
Subject: Re: [Boatanchors] restored radio question


> jeremy-ca wrote:
>
>> It appears that some old wives tales and other myths never die.
>>
>> New electrolytics, once reformed from a long rest, can be left alone for
>> many years again. Some of my collection doesnt get turned on for 5 years 
>> or
>> more after restoration and they suffer no ill effects. If an electrolytic 
>> is
>> an ancient original it was already starting the breakdown process when 
>> the
>> radio was stored, no amount of turning on will do anything except hasten 
>> its
>> demise.
>
> Not so. I've successfully reformed many old electrolytics and once 
> reformed,
> they work just fine. However, reforming requires several days, and running 
> the
> equipment occasionally, keeps them in good condition.


It all depends upon what you consider old. If a cap tests leaky then it is 
not a good candidade for reforming. Very few caps of the 30's have survived 
to today without developing leakage.

Later style caps are ruined by heat and set designers often liked placing 
them right next to the rectifier. For replacements in cans I always use 105 
*C rated and dont worry about the premium price.


>> Receiving type tubes, if not gassy when stored, wont be gassy in another 
>> 10
>> years or more. Some also attribute the glow from some beam tubes as gas 
>> when
>> in fact it is simply charged electron flow.  It is a different story with
>> some transmitting tubes that have an established reputation of having 
>> seal
>> problems.
>
> By operating old, slightly gassy, tubes in a tube tester with both 
> filament and
> plate applied, it is possible to degas receiving tubes. (The plate voltage 
> is
> needed because it's necessary to ionize neutral gas molecules before they 
> will
> react with some getters.) I've done it with several hundred WW II tubes. 
> About
> 90% are recovered using this technique. Occasional use will keep them 
> happy.

There is a huge difference between normal outgassing from the anode alloy 
and a slight drop in vacuum due to seal leakage.
The best way to recombine outgassing is to operate the tube at its rated 
dissipation or even slightly above for an hour or so. An easy way to do this 
is to use a unimportant radio that already runs its tubes hot and switch to 
SS diodes in the PS. If the xfmr fries its no big loss. This procedure will 
last for many years if not decades. A tube tester provides nowhere near the 
power necessary for many tubes.


  As
> to 'old wives' takes' I made careful engineering measurements on this 
> topic
> about 5 years ago. I wanted to restore some WS 19 sets to original 
> condition and
> had no desire to realign them, hence wanted to keep the original tubes in 
> their
> original location. Oh, and helium (present as a trace in the atmosphere)
> diffuses through most glasses, so even a tube  with perfect seals can go 
> soft.

Very true but a trace of helium does nothing to most receiving tubes except 
possibly some audio distortion. Cooking the anode will eliminate the helium 
and slightly poison the anode. I have no idea how many cycles it would take 
to ruin performance. Probably longer than anyone of us will live.

Carl
KM1H



>
>> Rubber insulation deterioates over time so be sure to check AC line cords 
>> at
>> every use.
>>
>> Carl
>> KM1H
>>
>> ----- Original Message -----
>> From: "J Forster" <jfor at quik.com>
>> To: "Gerry Steffens" <gsteffens at pitel.net>
>> Cc: <Boatanchors at mailman.qth.net>
>> Sent: Tuesday, October 09, 2007 11:23 PM
>> Subject: Re: [Boatanchors] restored radio question
>>
>> > IMO, I'd run each a few hours (say 4) every month or two. Here's my
>> > reasoning:
>> >
>> > Electrolytic capacitors need to be kept formed, and after reforming, a 
>> > few
>> > hours
>> > a month should be enough to keep them in good shape.
>> >
>> > Tubes need to operate a bit to prevent gas buildup. For this to happen,
>> > they
>> > need to be operated with BOTH filament and plate voltages applied. 
>> > BUT,
>> > I'd not
>> > run then so long that they get 'used up'
>> >
>> > FWIW,
>> > -John
>> >
>> >
>> >
>> > Gerry Steffens wrote:
>> >
>> >> OK Anchorites, what do you think about the following?
>> >>
>> >>
>> >>
>> >> I have approaching 300 radios in the collection.  Many work fine to
>> >> adequate
>> >> for now.  Many others have been fully restored.  Hopefully, more will 
>> >> be
>> >> restored after retirement in a few years.
>> >>
>> >>
>> >>
>> >> How often and for how long per session should these functioning radios 
>> >> be
>> >> turned on and used to preserve their functionality?
>> >>
>> >>
>> >>
>> >> Gerry
>
>