Comments on: About Vacuum Tube

By: admin

admin — Tue, 19 Apr 2011 23:59:41 +0000

HI Bob,

Thanks for sharing and you are right the components are getting smaller and smaller. Sometimes got to use a x10 magnifier to see those tiny components.

Jestine

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By: bob lou

bob lou — Tue, 19 Apr 2011 04:03:10 +0000

I remember the Vacuum tube TV's...I took my first electronics class in 1965, when I was 15 years old. I remember helping my father fix our tube tv, we would remove the tubes (they were all in sockets) and take them to the corner drug store. There they had a tube tester and we would check them. If any were found to be bad the drug store would sell us a new tube.

Later on I went to school to learn how to fix radios and television sets and it became a hobby. Later in life I went to work for a repair shop and then had to learn transistors. Now the new sets use small surface mount components. It's been interesting to see the changes in technology, I look forward to the future and what it will bring us.

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By: admin

admin — Fri, 11 Feb 2011 21:30:25 +0000

HI Yves,

Thanks for the info-appreciate that!

Jestine

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By: Yves Guillemette

Yves Guillemette — Wed, 09 Feb 2011 12:10:02 +0000

Hi Guys.

I've been in the electronics field for about thirty years. And tubes always fascinated me. There are good tutorial on the internet about them but I foud a book one day and it's ELEMENTS OF RADIO SERVICING. written by Marcus and Levy. Copyright 1947. yes it's an old one but it's been written by a technician for technician. awesome book. You will have to check on nthe internet it's there I downloaded a copy on a disk.

There is also a second edition(about 1950)

I recommend it personally I swear by it.

Yves

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By: admin

admin — Mon, 04 Oct 2010 23:46:38 +0000

HI Gerald,

That was a fantastic write up and hope the readers could benefit from these tips!

Jestine

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By: Gerald Musy

Gerald Musy — Mon, 04 Oct 2010 19:02:00 +0000

Vacuum tubes are beautiful devices, probably hard to find those days. I recently saw a shop in Hong Kong that seems to have many of them.
A tube that glows is not necessarily good. Actually the rupture of the filaments is rare, as they operate at much lower temperature than incandescent lamps.
A more common problem is when elements are getting loose and shorting with other elements inside the tube. By gently (softly please) hitting the tube with a small screwdriver’s handle one might hear cracking noises in the speakers, sometimes even see sparks inside the tube. If this happens, immediately turn the power off and replace the tube.
Another common problem is the tube losing its amplification over time. This usually comes from the coating of the cathode (usually aluminium oxide) becoming contaminated by gas molecules, thus the cathode emitting less electrons. This is diagnosed by injecting and tracing a signal though the various amplifiers’ stages (or just replacing the tube with a new one if you have one...).
Finally, many problems with vacuum tube apparatus are caused by shorted or leaking capacitors. Because they are submitted to high voltage (100 to 250 VDC) this is very common with old capacitors. A typical one is the capacitor linking two amplification stages (between the anode of the first tube and the grid of the following tube). A very small leak of this capacitor will polarize the grid of the next tube in such a way that it will produce a high distortion or simply not work.
A word of caution, vacuum tubes need high voltage to operate. Any area within the equipment is dangerous. Be careful.
Cheers,
GM

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By: admin

admin — Mon, 04 Oct 2010 00:12:19 +0000

Hi Kent,
Thanks for the info but sorry this WordPress does not have plug in to support photo or may be i could not find such plug in.

Jestine

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By: Kent Liew

Kent Liew — Sun, 03 Oct 2010 14:46:05 +0000

Hi Jestine,
When i saw this article, i suddenly remember i got one handbook for Vaccum Tubes. I had took some picture about this book but this comment plugin not allow to upload the files. Actually this book title is call "ELECTRON TUBES HANDBOOK". This book was printed on August 1975! Hope this helps!

Thanks,
Kent

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By: beh

beh — Sat, 02 Oct 2010 19:04:29 +0000

OK i want add that in old models of vacuum tubes sets there is no any smps
power supply is linear and a big ac step down transformer
is noticeable one ac input and many ac out put with different voltages
and also big watt resistors are most problematic after vacuums
they have big watt like 20-50 but low ohm like 2-50 ohmic value
as filter for ripples a very big can electrolytic do the job 2-5
cap in one can one negative pin and many positives for different voltages
above mentioned resistors job is dividing the voltages for different part of the set
thnx
beh

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By: beh

beh — Sat, 02 Oct 2010 04:12:37 +0000

ok i have to add that the vacuum tubes are working with a heater
and the heat warm s the cathode of lamp and cathode start to emit the electrons......so and so in those sets that the heaters of lamps are in parallel in circute to find the bad tubes is very easy because there is no light on that vacuum but in those ones that the heaters of tubes are in sire with each others in circuit is more difficult because
when one heater blow all the set goes off and we should check all the lamps to find bad one vacuum tube checker is good equipment for this job
thnx
beh

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