Hi guys, I recently had an idea about extending my tubes life and also incorporating a standby regime into my amp. So the general idea is to keep all the tubes at reduced heater voltage (around 3V) with no HV supply connected. When an input signal is detected the heater voltage will jump to 6.3V and after 10s the HV voltage will also be enabled. When you disable the input signal, the ON regime will stay enabled for around 6 minutes, after which the heater voltage will be brought down to 3V again and the HV voltage will disengage. I designed the schematic and all, I just need a confirmation if this is something worth pursuing, and if whether the tubes life will extended or not by this little exercise. All my tubes are somewhat old and some of them valuable, so every extra hour I can juice from them is an advantage. Here`s the circuit.
An externally hosted image should be here but it was not working when we last tested it.
Not worth it. See here The Tube CAD Journal,SRPP Optimal Rak Value 4
If i was so concerned about tube life, i would do the following:
1. Run the tube with constant current, instead of constant voltage. This will protect you during cold starts by preventing excessive current.
2. Slightly under-current the heater. This will result in less gm but also less gm degradation throughout the tube life. See here The Tube CAD Journal: Voltage regulators for the 2A3
One more thing to check is to ensure heater-cathode voltage limit is respected.
If i was so concerned about tube life, i would do the following:
1. Run the tube with constant current, instead of constant voltage. This will protect you during cold starts by preventing excessive current.
2. Slightly under-current the heater. This will result in less gm but also less gm degradation throughout the tube life. See here The Tube CAD Journal: Voltage regulators for the 2A3
One more thing to check is to ensure heater-cathode voltage limit is respected.
So long as the heater transformer isn't grossly over rated it should limit the current to the heaters on cold start.
Also heater (filament) failures are comparatively rare IMLE. Not the usual cause of tube failure.
Running tubes at reduced filament voltage and no plate current is a recipe for cathode poisoning unless the tube in question was designed for this mode of operation. (Tubes used in "instant on" TV sets were, but very little else in the consumer market was.)
Running tubes at reduced filament voltage and no plate current is a recipe for cathode poisoning unless the tube in question was designed for this mode of operation. (Tubes used in "instant on" TV sets were, but very little else in the consumer market was.)
No additional info except I am in awe of your signature line and will be stealing it....
Yes, a warm heater but no cathode current is a good way to shorten valve lifespan. The best way to get the best life out of a valve which is only required for intermittent duty (as in a domestic audio amplifier) is to switch it off when not being used and switch it on when it is needed. Avoid 'standby' switches and other such nonsense; at best they do nothing, at worst they do harm.
Wait, doesn't catbode poisoning occur only if you supply the tube with HV, while the cathode is not properly heated? And, I designed it so that it'll latch for 6min after a signal is detected, so It won't miss every song's 10s.
Run a valve with heater on but no cathode current and you get a cathode interface layer, also known as sleeping sickness. It may be that this happens more slowly with a lukewarm heater, but I would not wish to try it with a valuable valve.
Run a valve with lukewarm heater and significant anode current and you get cathode bombardment by positive ions.
Two ways to get long life:
1. leave it switched on and running - best if you need it running most of the time anyway
2. switch it off when not in use
Anything else is likely to reduce life.
Run a valve with lukewarm heater and significant anode current and you get cathode bombardment by positive ions.
Two ways to get long life:
1. leave it switched on and running - best if you need it running most of the time anyway
2. switch it off when not in use
Anything else is likely to reduce life.
What if I leave some anode current when the heater voltage is down?. For instance some 2-3mA? Or just keep the circuit as it is, and exclude the 3.3V heater supply.
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10 years is offly optimistic for any user grade tube. Maybe some military grade, but whatever I do, I won't get 10 years, for sure
NOS valves routinely ran for 20-30 years in small signal stages, except in TV sets where they overheated. 5-10 years for an output valve or rectifier?
Yeah, but I'm talking output tubes. ECC83 is easily replaceable. I have the european, the russian and the american equivalent, so it won't be a problem. But the output tubes are a matched pair and cost me 20 bucks each. So my efforts are mostly directed towards the power valves. I may even push them almost in class B, because now they're working at 300V with 38mA cathode current
Hundreds of TV, radios and industrial set ran for decades without any kind of soft start circuitry in their heaters. My old B&W TV ran about 30 years, and never I replace a heater defective valve. And it was about 12 hours at day powered on.
I believe it is completely unnecessary.
I believe it is completely unnecessary.
Starting in the 1960s, TV sets in the USA had a diode placed across the switch for the filament string to run them at half power. This was known as "Instant On".
This did not degrade product life to any noticeable amount.
This did not degrade product life to any noticeable amount.
> cost me 20 bucks each.
Say they last just 2,000 Hours.
That is $0.01 per hour.
What other fun can you have for one cent an hour?
Going to movie theater? $10++/hour
Drinking at the tavern? Any less than $5/hour, they throw you out.
Driving around in the country? Costs me $4/hour for gas.
Reading?? I pay $2 for a used book, if it keeps me amused for 2 hours that's a bargain. Sometimes I pay $13 for a book that's done in an hour.
20 buck tubes that last more than a few hours look like very CHEAP entertainment.
(Yes, times two per pair, and two channels, and six stages.... it is still hard to approach a buck an hour.)
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Agree that, _not_ including series-string radio/TV, heater failure is almost unknown in my half-century experience. Sometimes we banged them on as needed, sometimes we left them on day and night, no difference. Last one I saw was a partial failure in an H-P which had been *thrown* into a dumpster, after a long sad life in a university lab.
Say they last just 2,000 Hours.
That is $0.01 per hour.
What other fun can you have for one cent an hour?
Going to movie theater? $10++/hour
Drinking at the tavern? Any less than $5/hour, they throw you out.
Driving around in the country? Costs me $4/hour for gas.
Reading?? I pay $2 for a used book, if it keeps me amused for 2 hours that's a bargain. Sometimes I pay $13 for a book that's done in an hour.
20 buck tubes that last more than a few hours look like very CHEAP entertainment.
(Yes, times two per pair, and two channels, and six stages.... it is still hard to approach a buck an hour.)
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Agree that, _not_ including series-string radio/TV, heater failure is almost unknown in my half-century experience. Sometimes we banged them on as needed, sometimes we left them on day and night, no difference. Last one I saw was a partial failure in an H-P which had been *thrown* into a dumpster, after a long sad life in a university lab.
Old tube circuit Seeburg juke boxes had a system, the 6v heaters were always on. Then whenever the motor came alive (to move the mechanism, pick up a record, and spin it), a relay turned on the HV power transformer, which supplied 5v for the recto tube and the B+ supply. Small tubes could indeed last the life of the juke box, even though their heaters were on full for 16 hours a day, every day. And the power tubes, while only supplied B+ while playing, could also easily last years. But I think the main reason for it was to prevent noise while the box was idle.
The rectifier tube came up pretty quickly, so by the time the record was placed and started to play, the B+ was up. I recently ran a lot of power tubes through my tester, looking to cull bad tubes from my used stock. I found that a typical 6L6 or EL34 took 30-40 seconds after a cold start to come up to speed. That would have been too long to wait for a juke box. I didn't measure them, but are not tubes like 12AX7 about 11 seconds by design?
The rectifier tube came up pretty quickly, so by the time the record was placed and started to play, the B+ was up. I recently ran a lot of power tubes through my tester, looking to cull bad tubes from my used stock. I found that a typical 6L6 or EL34 took 30-40 seconds after a cold start to come up to speed. That would have been too long to wait for a juke box. I didn't measure them, but are not tubes like 12AX7 about 11 seconds by design?
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