#1
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Important to test tubes after recapping a non-working TV or radio?
Just wondering if I run any risk of damaging components if I try firing up a radio (1946 Westinghouse) or TV (1956 Packard Bell) after recapping the chassis if the condition of the tubes is unknown? I don't have a tube tester myself although I may be able to get them tested locally. If there is little to no risk of damage then I'd like to fire them up and see what happens and only mess with testing/replacing tubes if I still have a problem.
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#2
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Not much risk of damage but it's nice to know if your tubes are in top condition or not.
They can often have shorts or be weak and still basically function. I just finished recapping an Admiral but the vertical wouldn't lock, turned out to be a weak Sync tube, it also had four bad 6AU6 tubes in the i.f. section, performance was greatly improved after replacing them. |
#3
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You are on the right track IMHO. Just be sure things are coming
up as they should, audio on the radio & HV on the TV. Keep in mind the only bigger liar than a tube tester is a politician ( both parties). They have there uses but its best to deal with problems one at at time & not look for miracle cures. You learn more that way anyhows. Many of the low level tubes can be bought cheap also & they are the ones that can bring a set from working OK to working like new. Subbing a known good tube is the best checker. We had a top-o-line B&K checker at the shop and never used it. It was for the customers & the best salesman we had. Back then there was 60%-90% mark up in tubes and that was for name brand ones ! We did use a little checker. Plug in a tube & if the light lights the filament was OK. Saved time on series filament sets. 73 Zeno |
#4
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Thanks guys!
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#5
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If you later run into issues , its good to test the tube in that stage, or swap another tube in if you have one. One reason i use my tube tester is when i buy something off ebay, sometimes tubes develop shorts from being bumped in shipment, so I will usually run the tubes past my checker mainly to look for shorts, and weed out some weak ones as a side benefit. Radios and hifi rarely run the tubes hard, and often seem to work fine with rather weak tubes. Many TV circuits seem to be less forgiving of tubes, and may need a strong tube to work best.
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Audiokarma |
#6
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Quote:
Anyways, that's a piece of equipment I likely won't add to my collection no matter how much tube stuff I get. |
#7
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For the money you might spend to aquire and restore a good tube tester like a Hickock, you could get a stock of spares for most tubes. Can still pay to keep an eye out for em though, i found one hickok in an antique store for $40, and got another from a co-worker cleaning out his dads estate.
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#8
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Very often the best tube tester is the TV or radio itself. There's the "seven seconds off" test which is useful for showing up borderline weak tubes.
With the set running and warmed up, turn it off for about 7 seconds, and back on. Is the width slow to fill out? That'd be a borderline Horiz out tube. Vertical slow to fill out? Weak vert. out tube. Horiz sync slow to lock in? Hor. oscillator weak. Pic comes in snowy, then clears up? Weak RF amp tube in tuner. Etc. Then there's the 'tap test' useful for showing intermittent tubes. Tap each tube gently with something like a screwdriver handle while watching the pic (use a mirror if necessary). Intermittent heater-cathode shorts in the CRT often show up by tapping the neck. Damper tubes are notorious for arcing, and will almost always respond to the tap test (no mirror necessary). |
#9
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Unless a tube has a BAD short it is unlikely to do harm if bad and ran in a set....The one big exception in TVs is the horizontal oscillator tube...If bad (or the circuit it is in is bad) the horiz. output tube will red plate which which if allowed to persist for any significant period of time (more than half a minute) will destroy said output tube and possibly the flyback.
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Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
#10
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I test them for shorts after two bad experiences.
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AUdubon5425 Youtube Channel |
Audiokarma |
#11
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One thing to check: be sure each socket has the right tube in it! Somebody ahead of you may have just stuck tubes into sockets without regard for matching tube numbers to chassis position. Wrong tube means set doesn't work, OR fireworks!
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Reece Perfection is hard to reach with a screwdriver. |
#12
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Gotta say, I disagree with those that don't use a tube tester.
No, it's not an absolute, but I'll say this....I'd rather play it safe than sorry. I have a big drugstore type tester. If I see something with low or no emissions, it saves me a lot of potential diagnostic work after a recap. That, and the aforementioned short test. I don't see how anyone can reliably use vintage sets regularly without one. It's kind of like restoring sets without owning a meter.
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"Restoring a tube TV is like going to war. A color one is like a land war in Asia." |
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