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About Vacuum Tube
By Jestine Yong on October 1, 2010
Once in a while i do receive emails whether i could repair vacuum tube amplifier and other equipment that was related to vacuum tube. I gently told them i was not from the vacuum tube era thus i could not provide any answer to them. The first electronics class that i had attended was in 1987 and at that time semiconductors already long time taken over the functions of vacuum tube. There are some repair techs that are still repairing this type of equipment. If you are one of them we would like to hear from you-is it easy to repair, is there any difficulty in getting parts, is there equivalent tubes and etc? Thanks.
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beh
October 1, 2010 at 10:19 pm
hello jestine
these vaccum tubes are very interesting components and they are the mother of transistors
beh
karlo
October 2, 2010 at 1:23 am
I repaired just one Vacuum Tube amp years ago. It is removable from the socket so I just replaced it with exact parts. We just went to the store where my uncle bought the unit. The one that I replaced was obvious because the rest can be seen with their glowing filaments.
I think because vacuum tubes are rare nowadays, a replacement maybe difficult to find compared to solid state devices.
admin
October 2, 2010 at 2:27 am
Hi Guys,
Yes, my friend did told me before that look for the one that did not light up. It was an easy way to troubleshoot it.
Jestine
Waleed
October 2, 2010 at 2:41 am
My dad used to have a tv set that runs on tubes..I remembe when I was 15 years old(I am 42)and the back of the tv was exposed..no cover..I used to mess with the tubes..sometimes I get electrical shock..it hurts but I learned my lessen.
when the tv has a problem with the verital deflection..I used to change the tube marked PCL 82 because I could see that it is not lighting up..so I replace it and the tv works fine..sometimes, to repair the tv was just dusting the tv and it works for a while..the name of that tv was written in arabic..Ramsis..but it was a good tv set..
admin
October 2, 2010 at 7:52 am
HI Waleed,
That was a good sharing-thanks!
Jestine
beh
October 2, 2010 at 12:12 pm
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
beh
October 3, 2010 at 3:04 am
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
Kent Liew
October 3, 2010 at 10:46 pm
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
admin
October 4, 2010 at 8:12 am
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
Gerald Musy
October 5, 2010 at 3:02 am
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
admin
October 5, 2010 at 7:46 am
HI Gerald,
That was a fantastic write up and hope the readers could benefit from these tips!
Jestine
Yves Guillemette
February 9, 2011 at 8:10 pm
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
admin
February 12, 2011 at 5:30 am
HI Yves,
Thanks for the info-appreciate that!
Jestine
bob lou
April 19, 2011 at 12:03 pm
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.
admin
April 20, 2011 at 7:59 am
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