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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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Vacuum tube testing
A couple days ago I picked up several hundred tubes at an estate sale,
for $10. The estate was that of a fella in town who used to repair televisions. He died a couple months ago and his family is cleaning out a huge barn in which he had much of his old gear from his repair days. The tubes are still in their original boxes. Other than using a tube tester, is there any way to check to see if they are any good? For instance, a couple I have looked at have dark spots on opposing sides. SOme have a dark spot on just one side. Does this indicate the tube is dead, or is it how the tubes look new? Would it be common practice to put the old tubes in the boxes the new tubes came out of? Do tv repairmen have any reason to keep dead tubes? I suppose I could open the back of an old working tv and compare those tubes with the tubes I bought. |
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Vacuum tube testing
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#3
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Vacuum tube testing
The silver area inside the vacuum tubes were called "getter flashes" and
were left when a chemical coating was burned or flashed from a small element inside the tube in the manufacturing process. That process removed the remaining air in the tube. If the tube is cracked, the getter flash will turn white and flake off the glass. As for why the tubes were placed back in boxes, (1) It was the safest way to transport them without breakage (2) There was often a market for marganal tubes among hobbyists (3) A common practice with intermittent problems,was to "shotgun" or replace all the tubes that might cause the problem.Many of the ones removed were good. The repair shops would often use those tubes ( after testing) to repair used sets for sell. The bad side is that many techs would sell these questionable tubes as new. It sure did a lot of harm to the image of the honest wrote in message ... A couple days ago I picked up several hundred tubes at an estate sale, for $10. The estate was that of a fella in town who used to repair televisions. He died a couple months ago and his family is cleaning out a huge barn in which he had much of his old gear from his repair days. The tubes are still in their original boxes. Other than using a tube tester, is there any way to check to see if they are any good? For instance, a couple I have looked at have dark spots on opposing sides. SOme have a dark spot on just one side. Does this indicate the tube is dead, or is it how the tubes look new? Would it be common practice to put the old tubes in the boxes the new tubes came out of? Do tv repairmen have any reason to keep dead tubes? I suppose I could open the back of an old working tv and compare those tubes with the tubes I bought. |
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Vacuum tube testing
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#5
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Vacuum tube testing
wrote in message ... A couple days ago I picked up several hundred tubes at an estate sale, for $10. why? The estate was that of a fella in town who used to repair televisions. He died a couple months ago and his family is cleaning out a huge barn in which he had much of his old gear from his repair days. The tubes are still in their original boxes. Other than using a tube tester, is there any way to check to see if they are any good? yes... you can try them in circuit. that is replace an identical working tube and see if the unit still works. For instance, a couple I have looked at have dark spots on opposing sides. SOme have a dark spot on just one side. Does this indicate the tube is dead, or is it how the tubes look new? Would it be common practice to put the old tubes in the boxes the new tubes came out of? Do tv repairmen have any reason to keep dead tubes? often broadcasters would keep weak tubes on hand as emergency spares. the common practice was to write "weak" or "used spare" on the box and/or the tube. TV, radio and 2-way service techs in general would not want to grab a questionable part during a repair. I suppose I could open the back of an old working tv and compare those tubes with the tubes I bought. id check and see if any were made in China and use those for target practice. nothing political it is just that all the Chinese tubes i have seen either do not work correctly or do not last long. |
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Vacuum tube testing
Some of my own reasons to keep old tubes in new boxes we
1. Anal retention: can't throw away anything that had some potential life (never kept one with an open filament) 2. Proof to the customer of what they where paying for 3. Even if the customer did not take them back, I always kept them in case a few days later the customer came angry saying that the tubes did not fixed the problem, and "I want my old tube(s) back" :-) 4. If the filament was still good they could be used to complete a series when testing. Some tubes were designed to work in series i.e(27, 35,...=110V) 5. Looking at the pile of old tubes was kind of an index of how good the business was going. (just likea pile of extracted teeth are to dentist's success) I had two caddies: the NEW Stock, and the USED stock. I never sold nor recommended to use an old tube. I did had a lot of fun breaking them and examining the marvelous and mysterious design inside. It was much more fun and instructive than today breaking a 16-pin IC chip to check the inside :-) wrote in message ... A couple days ago I picked up several hundred tubes at an estate sale, for $10. The estate was that of a fella in town who used to repair televisions. He died a couple months ago and his family is cleaning out a huge barn in which he had much of his old gear from his repair days. The tubes are still in their original boxes. Other than using a tube tester, is there any way to check to see if they are any good? For instance, a couple I have looked at have dark spots on opposing sides. SOme have a dark spot on just one side. Does this indicate the tube is dead, or is it how the tubes look new? Would it be common practice to put the old tubes in the boxes the new tubes came out of? Do tv repairmen have any reason to keep dead tubes? I suppose I could open the back of an old working tv and compare those tubes with the tubes I bought. |
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Vacuum tube testing
I don't know if this is called "top-posting", but I backed up to reply here.
As the tube is used, usually more "crap" gases would un-disolve from the metal elements. This would usually cause a brown, or lighter ring around the getter. A nice shiny getter is a good indicator, but not 100%. If you can't test them but want to sell them it's a piece of info that might help. JURB |
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