Re: Obituary(s) To A Filter Cap And A 6X4 Rectifier Tube


Steve Ireland <vk6vz@...>
 

Hello Sam
 
Thanks for the great reply. Well, I am a 62-year old teenager doing exactly the same thing as you. 
 
Got my ham ticket back in 1971 at the age of 15 when Drake 2Bs were just about the coolest radio you could buy if you liked CW, but were way beyond my price range.  My entire station back then – an HRO MX and 10W CW transmitter using a Geloso VFO – cost 20 UK pounds and was paid for by my newspaper delivery round.
 
In recent years I’ve restored a Drake R-4A and the 2B (although I did a couple of C-lines and a B-line about 10 years ago) and so far have been lucky with the Chinese electrolytics purchased online or from a local hobby shop called Jaycar.  However, your idea about always using a sensibly rated fuse in the transformer primary is a good one and made me think that perhaps I am beginning to push my luck. Putting in a fuse in the old radios where there is always room is pretty easy too. 
 
I’ve also been working on a very early Drake TR-7 and fused the line between 12V supply and this radio without even thinking. Thinking about it (thanks to your nice piece of writing), there is more of a need to fuse an older radio like the 2B using valves and large electrolytics than there probably is the TR-7!
 
I shall severely admonish myself and start putting sensibly-rated fuses in any old valve radios I resurrect that don’t have them.
 
Vy 73 
 
Steve, VK6VZ
 

Sent: Monday, June 05, 2017 10:47 PM
Subject: Re: [4sqrp] Obituary(s) To A Filter Cap And A 6X4 Rectifier Tube
 
 

Hello Steve,

Thanks for the condolences. The replacement filter cap is working well at
about 75VDC below it's maximum rating. the replacement is running cool being
in the transmit mode all the time - or off. I will check ir again (
temperature ) before putting it back on the operating position. Right now it
is still on a workbench.

I buy in bulk a flea=markets and install one in every rig when I first put it
on the air. I try to fuse it just above the " blowing " point, installed in
one of the 110 VAC primary power leads going to the power transformer.

the fuse holder that permanently mounts on the chassis, with a little cap you
unscrew to replace the bad fuse if the type I like to use. Quick and easy and
you don't have to take the cabinet/cover off to get to the spent fuse.

On some of the older transmitters like the classic Heath-Kits - AT-1 and DX-20
have thicker steel chassis and then it is easier to mount a " one bolt holds
it in place ", but it makes replacing the fuse more difficult.

Steve, basically I am a 75 year old teen-ager re-living my mis-spent youth
buying these 60 + year old radios I couldn't afford when I was a kid and using
them today.

I also have other radios running full time, a pair of Iom 756PROIIs and an
Icom 765PROIII I just bought from the estate of my lifelong friend which
reminds me I need to " thin our the herd somewhat here.

At Christmas time, one of the big market items are fruit cakes - and their
main good point are the cans they come in, which I use to store parts/wire/and
fuses in. I got tired if buying expensive fuses one at a time, and started
buying assortments in bulk at flea-markets, and now I have a fruit-cake can
full of almost every possible fuse I might need.

Sorry for the long outpouring on this subject. It is raining cats and dogs
here in east Texas rifght now and I am trapped in my detached shack - not a
bad way to send the day.

Keep the operating Voltages well below the ratings stamped on them!

73,

Sam Neal N5AF
Celebrating 60 Years In Amateur Radio

And the filter cap is still running cool to the touch.

------ Original Message ------
Received: Mon, 05 Jun 2017 04:01:23 AM CDT
From: "'Steve Ireland' vk6vz@... [4sqrp]" <4sqrp@...>
To: "Sam Neal" , <4sqrp@...>
Subject: Re: [4sqrp] Obituary(s) To A Filter Cap And A 6X4 Rectifier Tube

G’day Sam

Your email made me laugh aloud – although not at the tragedy of course.

I may be laughing on the other side of my face soon, having just replaced the
multiple capacitor-in-a-can in an old Drake 2-B with four Chinese 450V
electrolytics. The rectifier whose bumps they are smoothing out just happens
to be a JAN 6X4. Maybe I should think about a fuse?.. ;-)

Have a great day, mate.

Vy 73

Steve, VK6VZ

From: mailto:4sqrp@...
Sent: Sunday, May 28, 2017 4:13 AM
To: 4sqrp@... ; amecoac1@... ; GQRP@... ;
AQRP@... ; regenrx@... ; Robert Melton ; Sam Neal
Subject: [4sqrp] Obituary(s) To A Filter Cap And A 6X4 Rectifier Tube

Hello,

I sadly report the passing of two QRP radio transmitter components.

( #1 ) Passing ( Suddenly! ) of a 22 mFd/450 Volts DC Filter capacitor.

Born approximately 2007 in China ( The People's Republic There-of )

Passed ( suddenly ) just before the 4 States QRP Group Net, 0130 Z - 7122 kHz
-
24 May, 2017 at 01:15:05Z

Born in People's Republic of China to operate continually at 450 VDC.
Passed suddenly and in a spectacular manor while operating at approximately
380 VDC

We also sadly report the associated passing of two 1 Ampere fuses and one 6X5
Tube.

__________________________________________________________

( #2 ) Suddenly, 01:15:06 Z one 6X5GT/G CHS/Jan rectifier tube.

6X5/GT/G/JAN/CHS served proudly during the World War 2 conflict assigned to
the United States Navy.
Two innocent 1 Ampere fuses lost their lives as a result of the above
incident.

Services will be This coming Wednesday by the P&H Garbage Pick-up Service
Company
Pall-bearers will be Cooter and Bubba.

Internment will be shortly there-afterwards at The Liberty County Texas
Landfill

=========================================================================================
=========================================================================================

This is the first failure I have had with these small sized fiter caps. I
suggest operating these imports will below heir rated Voltage limits. The
above components were in the built-in power supply of a clone-kit of an Ameco
AC-1, with a Ken-Rad 6V6 tube as a crystal oscillator.

The transmitter was not being used when the filter cap failed, just minding
it's own business, awaiting net time.

The current rush took the 6X5/G/GT with it, and it's rolling off the desk top
and playing Humpty Dumpty didn't help it any at all. So far, no problems with
the replacement 22 mFd. 450 VDC cap.

All kidding aside, have any of you had problems with these type capacitors,
operating well below their operating Voltage, failing? The value and Voltage
ratings are well marked, but no manufacturer's info is shown. I either bought
them in small lots off of E-Bay purchases, or the filter cap was supplied
with
the kit - I forget.

Due to failure with 50+ year old paper filter caps in older boat anchor rigs,
I routinely replace the filter caps and also add a fuse before ever
transmitting the first dot with them. I had hoped that operating well below
it's Voltage rating would help, but it didn't.

Any comments on similar incidents would be appreciated.

73,

Sam Neal N5AF

Celebrating 60 Years In Amateur Radio
----------------------------------------------------------

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