kodabmx,
Half heat, eh? Good for "instant on", but for oxygen cathode poisoning, it's even worse.
When I was in high school, all TV's were back and white tube jobs. I worked Saturday mornings in a TV repair shop, fixing TV's and stereograms that the field techs (actually tube jockeys or not much better) brought back to the shop because changing a tube wouldn't fix it.
They made good money out of "rejuvenating" tired picture tubes by boosting the heater voltage - we carried a stock of small transformers for that purpose, just as you described. Typically the pix tube would carry on for a few more months, maybe a year.
Back, then, TV's cost a month's wages, and replacing a pix tube 2 to 3 weeks wages - tube, labour, including general check, replace any other weak tubes, lubricate tuner, pots, etc. If you quoted that cost to housewives, some would cry. Then, you'd tell them you could rejuvenate the tube for a few dollars, and they would smile and be happy again - for a while. All that fuss over Gunsmoke and I Love Lucy in low definition black & white.
Half heat, eh? Good for "instant on", but for oxygen cathode poisoning, it's even worse.
When I was in high school, all TV's were back and white tube jobs. I worked Saturday mornings in a TV repair shop, fixing TV's and stereograms that the field techs (actually tube jockeys or not much better) brought back to the shop because changing a tube wouldn't fix it.
They made good money out of "rejuvenating" tired picture tubes by boosting the heater voltage - we carried a stock of small transformers for that purpose, just as you described. Typically the pix tube would carry on for a few more months, maybe a year.
Back, then, TV's cost a month's wages, and replacing a pix tube 2 to 3 weeks wages - tube, labour, including general check, replace any other weak tubes, lubricate tuner, pots, etc. If you quoted that cost to housewives, some would cry. Then, you'd tell them you could rejuvenate the tube for a few dollars, and they would smile and be happy again - for a while. All that fuss over Gunsmoke and I Love Lucy in low definition black & white.
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I Love Lucy was a great show though 
I almost wish there was still a tube tester in the drug store... I'm too young to remember it in person, but I've read the stories... Imaging if modern tech was "user serviceable" again? Imagine if everyone knew how to solder Meanwhile, if I need to change the battery in my phione I need a heat gun to soften the glue, spudgers, suction cups, and the will to do all this without breaking the blasted glass!
I almost wish there was still a tube tester in the drug store... I'm too young to remember it in person, but I've read the stories... Imaging if modern tech was "user serviceable" again? Imagine if everyone knew how to solder
Meanwhile, if I need to change the battery in my phione I need a heat gun to soften the glue, spudgers, suction cups, and the will to do all this without breaking the blasted glass!Ha! Those tube testers that the public could use for free were great money makers. We in Australia didn't have them in drugstores (rough equivalent in Australia were known as "chemists", or "jaydees"), but some Radio and TV shops had them.
Numbskull Joe Blogs would unplug all the tubes he could see, miss the one that was crook because it was behind the speaker transformer or inside the EHT cage, bring them in to the shop, test them all on the tube tester, buy a tube or 2 he didn't need (often the real problem was a resistor gone high, or a pot or switch gone noisey, but Joe though all faults would be tube faults), go home, break a tube, come back and buy another, go home again and put then all in the wrong sockets.
Then the set would come to us, we would replace the tubes in the right sockets, replace with new any that were stuffed up by being in the wrong socket (happened a lot with diode-pentodes as I recall), and any resistors burnt out by the wrong tube in the socket. Easy work and you could get a day's wages out of it.
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Reminds me - another great little money maker for us in the radio & TV repair game was that once in a while popular magazines would publish articles along the lines of "Diagnose your own TV fault". These had tables of symptoms and what tube to change for each symptom - eg no or weak sound - change the 6BM8; wishy-washy picture - change 6GW8; picture rolls - change 6CG8 (or whatever the tube was).
We might notice a temporary slight reduction in requests to attend to faulty TV's and a marked increase in people coming to buy one tube of a specific type, followed by a phone calls from the same turkeys to come and fix their TV. Either it wasn't the tube, or he just didn't understand the symptoms
We might notice a temporary slight reduction in requests to attend to faulty TV's and a marked increase in people coming to buy one tube of a specific type, followed by a phone calls from the same turkeys to come and fix their TV. Either it wasn't the tube, or he just didn't understand the symptoms
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Well, the opposite if capitalism is communism, as it was in the socialist paradise Soviet Union. Where NOTHING was free, should you even be able to find it.
Actually, the TV service industry back then was rife with dodgy operators. People like my boss, who employed an untrained schoolboy (i.e., me) to fix the "difficult" jobs were one of the good ones.
Most shops had their origins in ex-army signals mechanic and the like owners who knew what a wire was, a resistor, and a relay, maybe a vague understanding of what a capacitor did, and that was about it. Or old pre-war radio servicemen whose electronics knowledge just about extended to Ohm's Law and where to buy a crate of dodgy surplus tubes. They employed ex-sparkies (light and power electricians), gave them a 100W Birko soldering iron with a bit on it the size of your thumb, and a multimeter, and told them to go to it.
The major manufacturers eg Philips, Kriesler, AWA, had their own service departments for warranty repairs, staffed with relatively carefully selected techs with factory training. Otherwise their reputations would have been trash.
Nice discussion, gentlemen. Personally, I've never encountered problems running my tubes on heaters only, although the maximum I did, was for an hour per month during a period of three years or so. I had mercury rectifiers and a manual switch for heaters only and HT. Sometimes I would forget heaters for a half an hour, while doing house chores.
Customers could be rabid crooks too. Still can be, from what I've heard.
When I was working in TV repair, we had one joker who called us re a TV with poor sound. Our man found the 6BM8 was sick, replaced it, and Customer wascharged the standard fee - about $1.06 or something for the tube, $1.30 or something for labour, and another dollar for the callout. Going rates back then.
A week later the turkey rings up again - "sound has gone crook again - you didn't fix it right." TV was brought back to the shop. I took a look, nothing wrong except the 6BM8 had low emission. Replaced it and TV taken back to customer, no charge. The opportunity cost to us was several dollars, but we assumed it was a rare crook tube from the factory and wore it.
A couple of weeks later this turkey rings up again - same fault. TV brought back to the shop. I took a look, boss looking over my shoulder. Yep, the 6BM8 is crook again. Nothing else wrong - nothing that would affect the tube. But wait, the date code is several years back. Boss drove out and spoke to the guy's wife. Turned out they had a sick stereo, using 6BM8's as output tubes. Turkey has swapped one over with the TV. Then some mate of his had a faulty TV, so he did it again.
We had a local story about a CD player vendor and a buyer who wanted a specific model. The vendor sold him the CD player through mail shipment. A few days later, the client complained about a fault in the item and asked for a refund. The shipment was sent back and when the buyer attempted to repair it, he realized a module inside was missing when he opened it.
It turned out, the buyer took out the module to repair his own CD player of the same model.
It turned out, the buyer took out the module to repair his own CD player of the same model.
Fool me once, shame on you... I, like you guys did with that customer, give the person the benefit of the doubt. Nowadays, of the 6BM8 went low, you'd tell the person to take it up with the manufacturer anyway
My last customer got charged 20$ for parts, and "pay what you can" for labour. Most people are more generous than I thought, honestly.
Well, that got everyone chatting with each other... lots of good stories!
My final conclusion is that a stand-by on a HiFi amp is probably not worth the effort or the cost? However, I have learned that if you do want to do this then having separate transformers for the HT and the heaters would solve most problems as they can then be switched from an ordinary 240VAC switch.
My other idea that the power can be switched at the back of the amp by a Relay, instead of running 4 x 240VAC wires to a switch on the front, is possible but a nob on the front connected to a switch at the back with a connecting-rod is more popular so maybe that is the way to go for that one?
Thank you all for throwing yourselves into the discussion, it was worth it!
Roger and out
My final conclusion is that a stand-by on a HiFi amp is probably not worth the effort or the cost? However, I have learned that if you do want to do this then having separate transformers for the HT and the heaters would solve most problems as they can then be switched from an ordinary 240VAC switch.
My other idea that the power can be switched at the back of the amp by a Relay, instead of running 4 x 240VAC wires to a switch on the front, is possible but a nob on the front connected to a switch at the back with a connecting-rod is more popular so maybe that is the way to go for that one?
Thank you all for throwing yourselves into the discussion, it was worth it!
Roger and out
Nowadays, {I}f the 6BM8 went low, you'd tell the person to take it up with the manufacturer anyway
No, not in here in Australia, anyway. Under Australian law, when you buy something, be it a product (eg a car) or a service (getting your TV fixed), the legal position is that you and the supplier (car dealer or TV shop) have entered into a contract. There does not need to be a written contract.
A contract means Party A has agreed to supply something that is fit for the purpose that it has been stated or implied for, and Party B has agreed to pay a sum of money for it.
You have no contract and therefore no rights against anyone you haven't paid money to.
If you are not happy with what you got, you must take it up with whoever you have a contract with. Whoever supplies the firm you have been dealing with has nothing to do with it. However they normally would have a claim with their supplier, i.e., the car manufacturer or the tube supplier.
If a TV repair business replaces a tube in a customer's TV set and it turns out to be crook from new, the customer has a right to claim against the TV repair business, not against the tube maker. However the TV repair business has a right to claim against the tube factory. We never bothered, it wasn't worth the time and effort over something worth only a dollar or so. Speakers were worth quite a bit more - we sent flawed speakers back to the factory for exchange.
Same with a car - if it goes faulty due to a manufacturing flaw, the buyer has a claim against the car dealer. Its no good him going to the manufacturer. But the car dealer can - they get parts and labour paid by the factory.
I thought the law in this regard was the same in North America - its a good sensible way to do things.
There is an interesting quirk arising from the law and standard business practice. If you buy a TV or stereo or something else electronic of significant value from a retailer, they often give you a piece of paper telling you where to take it if it's crook during the warrantee period. It will be the manufacturer's local service outlet or a repair business under contract to the manufacturer - their agent. This means you get your product fixed by somebody who should know what they are doing, and the retailer doesn't have to hire technicians. Now, if your TV or whatever goes crook and you take it to the nominated service agent, and then you genuinely believe that agent didn't or wouldn't fix it properly, you still have a claim against the retailer. Good luck with that one though.
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If I buy a hard disc from Canada Computers, and there is a problem within 7 or 15 days, I can return it to the store for DOA warranty. If it's past that date, I take it up with Seagate directly. Some companies hanlde this for their customers but not all.
Same with my cell phone. If it becomes defective within 15 days of purchase, they will do an exchange, otherwise you deal with manufacturer warranty.
Now most companies offer warranty upgrades for a fee that provide an instant replacement with an equal or better item.
Same with my cell phone. If it becomes defective within 15 days of purchase, they will do an exchange, otherwise you deal with manufacturer warranty.
Now most companies offer warranty upgrades for a fee that provide an instant replacement with an equal or better item.
kodabmx,
Some companies here in Australia will replace with new a dud product on demand within a limited time period after purchase. Some companies here will refund your money within a limited time period. Some companies will give you money back within a VERY limited time period and you don't have to give a reason. You can just change your mind and not want it. Never on a car though, never on something built just for you, and never on underclothing. For outer clothing its pretty standard. Standard for loudspeakers (but not drivers on their own) - the quality sound trade considers it normal that you might need a week to see if you like the sound of speakers. If you don't like, you can bring back, provided you haven't damaged them (eg scratches on wood, burnt out because you fed a 50 W speaker with a 1000W amp.) On furniture they typically will take back within 7 days and refund, less a handling fee.
But none of the above is legally enforceable. All they are legally compelled to do is make good the fault, if any.
On the other hand, it can be surprisingly good. I bought a 6-cylinder Ford Falcon car some years ago. Drove it for nearly 2 years, (Ford warranty then was only 1 year) and was proceeding along and suddenly the engine started to make an extremely loud rattling noise and running on only 4 cylinders. By luck, I was within 100 m of a Ford dealer, so drove it straight in, and asked them to fix it. They rang me later - camshaft had broken. Dealer guy said that is not wear and tear - it just should never happen. They got Ford to pay for new camshaft and engine partial disassembly and rebuild. "Manufacture was not fit for purpose, not what an owner could reasonably expect."
The word "partial" worried me a bit, but I drove it for another 10 years without any mechanical trouble at all. (plastic door trims eventually warped badly though, and driver's seat eventually fell apart - typical Ford.
Some companies here in Australia will replace with new a dud product on demand within a limited time period after purchase. Some companies here will refund your money within a limited time period. Some companies will give you money back within a VERY limited time period and you don't have to give a reason. You can just change your mind and not want it. Never on a car though, never on something built just for you, and never on underclothing. For outer clothing its pretty standard. Standard for loudspeakers (but not drivers on their own) - the quality sound trade considers it normal that you might need a week to see if you like the sound of speakers. If you don't like, you can bring back, provided you haven't damaged them (eg scratches on wood, burnt out because you fed a 50 W speaker with a 1000W amp.) On furniture they typically will take back within 7 days and refund, less a handling fee.
But none of the above is legally enforceable. All they are legally compelled to do is make good the fault, if any.
On the other hand, it can be surprisingly good. I bought a 6-cylinder Ford Falcon car some years ago. Drove it for nearly 2 years, (Ford warranty then was only 1 year) and was proceeding along and suddenly the engine started to make an extremely loud rattling noise and running on only 4 cylinders. By luck, I was within 100 m of a Ford dealer, so drove it straight in, and asked them to fix it. They rang me later - camshaft had broken. Dealer guy said that is not wear and tear - it just should never happen. They got Ford to pay for new camshaft and engine partial disassembly and rebuild. "Manufacture was not fit for purpose, not what an owner could reasonably expect."
The word "partial" worried me a bit, but I drove it for another 10 years without any mechanical trouble at all. (plastic door trims eventually warped badly though, and driver's seat eventually fell apart - typical Ford.
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Why add something which does nothing useful? There is only a weak reason for a standby switch on a guitar amp, and even there some guitarists don't understand what it actually does. I once knew someone who insisted that his amp was left on standby for a few minutes after finishing 'so it could cool down slowly'; completely unnecessary but musicians always get what they want.jacksonsinliss said:
A valve with hot heater but no anode current will gradually develop a cathode interface layer unless it has a special cathode - which typically means a 'computer-rated' valve, not a normal audio valve. The result is a gradual reduction in anode current and gain, which may be confused with lack of emission. Note that this is nothing to do with gettering, oxygen or ion bombardment; it occurs at the interface between the cathode metal and the oxide layer.
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You are not correct. It's true that this problem was first detected in computers, but reputable tube manufacturers all went back to pure nickel cathodes and other types that don't suffer form this problem.
The thing is, what constitutes sufficient cathode current to inhibit the formation of the interface layer? Precisely zero? Obviously it would be ridiculous to believe that. A 12AU7 cathode is designed for 20 mA. In typically applications, it may have only 1 to 10 mA. Is 1 uA sufficient to inhibit an interface layer? That seems unlikely. What about 10 uA? What about 100 uA?
Have you ever seen anything in a databook or application guide that specifies the minimum average cathode current to prevent appreciable interface layer formation? No, you haven't. Yet in full data and app notes they go to some trouble to tell you to stay within the design limits for heater voltage - because that DOES matter.
In professional equipment and lab test gear, tubes are operated well inside ratings, to ensure stable operation and long life. Recommended 6BE6 operating conditions call for a cathode current of 3 mA, and that's about what it will have in its intended role - a converter in AM radios.
I have a Tektronix lab instrument that uses a 6BE6 as a signal gate. Its operating current is 0.2 mA. It still has the original tube (1954) and its still good. I checked its gm earlier this year (I calibrate and overhaul instruments once every few years) and its normal.
The same instrument has a couple of 6U8's (a favorite tube of Tektronix) operating the triode side at an average of 0.5 microamps, and 200 microamps peak under certain conditions. And nothing (zero) when the instrument is on but no input connected. Have they developed low gm, indicating an interface layer? Nope - still good.
In ordinary radios, tuners, etc, most of them more or less permanently tuned to a strong local station, the IF tube operates at a mere fraction of its design centre cathode current, due to AGC.
What about the detector diodes in AM receiver tubes? Typical operating current is less than 5 microamp, but they use a standard cathode, about 5-10% of the normal length of a triode. What about the 6AL5 FM detector diode? It uses standard cathodes - big enough you can use it as a rectifier (rated at 9 mA) in VTVM's, though this isn't particularly recommended. In FM detector service, it will pass only microamps. And they last 20 years or more.
The fact is, tubes with an interface layer had a built in 1930's manufacturing mistake that could affect service in things other than computer service. Once it was realized it was a mistake, they stopped doing it. (except perhaps Chinese tubes)
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I found this a while ago and forgot all about it. It may be interesting to you if you want to add a delay on the HT?
http://www.rubli.net/HT_delay/ax_aug-2001.pdf
http://www.rubli.net/HT_delay/ax_aug-2001.pdf
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