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Tubes are not so unreliable

While getting my hair cut, I remarked to my barber about his Zenith table radio. It featured FM, but seemed to be of mid-60's vintage. He confirmed that he probably bought it in 1965 or 1966. When I told him it must be tubed, he said it was. He has played it every day the barbershop has been open since the radio was purchased. I asked him how often he has had to replace a tube. The answer was, "Never, I have never touched anything inside of it." He didn't know how many or what types of tubes the radio used. His sentiment was that if a tube ever goes, he will have to retire it(but not get rid of it). That's when I told him to tell me if that ever happens. I will hook him up with the tubes. That was when Zenith was Zenith. Before the dark days; how they went from being the best to the worst. The radio was bought for the princely sum of $85. I wonder how much that would be in today's money. Enough to buy the WaveRadio I am sure. Now, who would ever suggest that someone buying the Bose would ever get 35 years of use out of it? I guess tubes are not so unreliable after all. So, for anyone who worries about buying tube equipment, you might want to think about this story
trelja
sean
6,231 posts
 
Power output tubes in RF gear take a beating. As such, one of my fellow "techs" uses a tube radio on his bench to test all of his repairs. The original tubes in the output section have been used on a daily basis since 1968 up until appr 2 years ago. He finally decided to change the output tubes. After all of those years of use and running at full output on a daily basis ( 7 days a week ) and having the tube run into amplifiers that had damaged input circuitry, the power output level was down only 22% as compared to a brand new tube of the same vintage. I don't know of ANY type of SS component that could lay claim to ANYTHING like that. Sean
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elwood
42 posts
 
Viridian, The real reason the Russions use tubes is to protect against EMP, electromagnetic pulse from the radiation of an atomic blast. They first noticed the effect on electrical transmission lines during an atmospheric test. The power grid shut down from overload. The same thing happens to solid state devices. The military knows this and shields their solid state against such a pulse. Tubes are resistant to the effect, but are not necessarily better than well shielded SS
tubegroover
2,320 posts
 
Interestingly enough I have a pair of MC-60's. One is from 1956 vintage the other later. I am the 3rd owner. I had the ORIGINAL 6550 output tubes in that amp until 1995. I don't know what that says about today's tubes but it sure tells me a bit about yesterdays as well as the engineering.

So far as the Zenith name brand that is all it is, a name brand that today has nothing to do with the quality that was once associated with it.
nrchy's avatar
nrchy
2,124 posts
 
The problem in most tube equipment is not the tubes but the way designers abuse them. Tubes can last nearly a life time unless they are pushed so hard to do things they weren't designed to do. Most new (the last ten or fifteen years) tube designs are very hard on the tubes. I have an old zenith tube radio older than that which still works although the power cord is worn. Maybe I'll replace it with a whale!!!
dekay's avatar
dekay
5,663 posts
 
Tubegoover: I had an old Eico HF-81 integrated amp with the same thing. I sold it in 1985 and it was still running the original EL84's which sounded fine.

Nrchy: I own an Audion Silver Night 300B stereo amp which does not run the output, input and driver tubes hard at all. This is a blessing, I agree, considering the cost of good 6922 and 300B tubes. The US rep has been getting around 5000 hours on stock Chinese 300B tubes in his personal unit, which means that my Svetlana's may be good for twice that (four times their regular life).
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