[Hallicrafters]V18#22; Electrolytic Fireworks

[Phil Barnes-Roberts WA6DZS]

hallicrafters-request at mailman.qth.net wrote:

> Re: Re: [Hallicrafters] Recapping Hallicrafters
> From:
> peter_may at optusnet.com.au
> Date:
> Thu, 14 Jul 2005 13:04:56 +1000
> To:
> k0ewu at juno.com
> 
> To:
> k0ewu at juno.com
> CC:
> radiocompass at yahoo.com, cnicolsen at msn.com, Hallicrafters at mailman.qth.net
> 
> 
> I once had an electrolyte formula for refilling wet type electrolytics.
> If anyone is interested, I'll look it up.
> I also struck the occassional 8 ufd perculating electro. The Ducon brand Australian ones sometimes had a little rubber valve in the lid.
> 
> Regards
> Peter
>=========================
> 
>>k0ewu at juno.com wrote:
>>
> 
> Harken ye back to the day of wet electrolytics, a tall round can,
> aluminum, the neg.
> side. The positive was an electrode in a bath of electrolyte, a water
> solution.
> 
> I was working in a gamble store repairing radios after school-- high
> school,
> The farmer that brought it in said it souded like his coffee pot.
> Shure did, I turned it on and it played for a bit, started to gurgle and
> then
>   pow!!  the lid of the can blew a hole in the top of the cabinet like a
> 12 gauge shell would, about 2 in diameter.  from that day forth i have
> always replaced a wet cap with a more modern one.           Before
> applying power.
> 
> jack
> 
> 
> 1
> On Tue, 12 Jul 2005 12:18:52 -0700 (PDT) Mike Everette
> <radiocompass at yahoo.com> writes:
> 
>>
>>--- "Clayton L. Nicolsen" <cnicolsen at msn.com> wrote:
>>
>>
>>>"One mistake some make is replacing electrolytic
>>>caps with one of a higher
>>>voltage, this will accelerate the aging of the cap.
>>>
>>
>>REST ASSURED!  THIS IS PURE BOVINE
>>BYPRODUCTS!!!!!!!!!!!
>>
>>Sounds like something dreamed up by some propellerhead
>>whizbang, raised on a diet of germanium and silicon
>>(especially when made into computers)....
>>
>>There is NO danger of jeopardizing a cap by using it
>>at less than rated working voltage.
>>
>>On the other hand, if one subjects some capacitors,
>>especially electrolytics, to ABOVE rated voltage, the
>>effect can and often does resemble Mount St. Helens. 
>>I once saw a can-type filter cap in a tube-type mobile
>>radio explode, and throw its guts 10 feet straight up
>>to stick on the ceiling of the shop (it was in an old
>>garage service bay).  It was LOUD, too.  
>>
>>And that is the absolute truth.
>>
>>73
>>
>>Mike
>>WA4DLF
>>

'----O'=o='O----'

Pass that formula on, if it comes to hand, Peter!  Most electrolytics 
come with some kind of a pressure relief port, though it may not be 
obvious at first.

I have an electrolytic story; it was at N0EFC at MAG-12, on the beach at 
Chu Lai RVN, in 1970, running phone patches into N0JPJ at Hughes 
Fullerton CA, just outside the ham bands on MARS frequencies.

I was in the middle of a string of calls, and the T/R relay inside the 
Collins 32S-3 gets dirty and needs a strip of teletype tape pulled 
between the contacts to clean it (that was our fix; the slight oil in 
the tape, and the yellow paper roughness, helped remove oxidation 
without being too hard on contacts.)  Rather than open the hot HV/RF 
final cage and fiddle with it, while callers are waiting and the band 
conditions are deteriorating, I swap-in the other transmitter, sitting 
on the other (vacant) operating position.

Now the S-line transmitters have the power supply in a separate chassis, 
often inside the phone patch/SWR bridge/speaker console, and connected 
by a fat cable with an 11-pin "octal-style" socket, and a plug on the 
transmitter to match.  This one had happened sometime previously to have 
had its indexing lug, the whole center post, broken off, so in a hurry, 
I plugged the thing in, plugged in the various RCA phono plugs (yes, 
including 100W RF-out to the linear!) and flipped the switch to warm up, 
so I could get back to servicing customers.

Naturally, Murphy had a hand ready to deal me.  The indexing was _only_ 
one pin off, which put primary AC on the bias cap, looking for about 
-100VDC to Gnd.  After a few seconds more of cooking, it hissed, and 
then BANG! launched itself across the under-chassis, leaving white crud 
and khaki confetti in its wake, letting out _all_ the magic smoke. 
Fortunately, it didn't take out anything else in its trip, and much 
later in the day, after some research, cleanup and replacing the cap, 
the (astonishingly well-designed) rig was back in business.  Don't know 
if that plug ever did get changed.  Meanwhile, to get back on the air, I 
bit the bullet and unscrewed the RF cage and cleaned my other relay - 
*Sigh*.

'----O'=o='O----'
RULES OF THUMB:
Replace electrolytics with the same or slightly larger capacity (MF's) 
and the same or a bit higher working voltage (WV) rating; a good rule of 
thumb is 50-to-100-percent safety factor in voltage.  Much more than 
that, and the cap never completely forms properly, and never quite 
reaches its rated capacitance.  If you have to do that, err on the side 
of a bit larger capacitance (that will still fit physically in the space.)

Do make sure of polarity; +/- swapped is another good way to watch your 
gear smoke!  Have fun, keep it safe!

73, Phil WA6DZS at ARRL dot net
A Task without a Due-Date is a Fantasy!
'----O'=o='O----'