Second that motion, though a 150 or 160 will afford adequate protection as well. Gorden Gow knew his stuff. Enjoy the music.
An NTC thermistor does its work in about .1 sec. They are designed to protect the rectifier during the charging cycle that ends very quickly. The caps don't care about the inrush at all unless the voltage peaks well above the WVDC rating and stays there for more than 1 minute. You should use voltage rated caps that factor in your unloaded voltage peak and forget about the thermistor. It won't be working long enough to matter unless you are using diodes with insufficient peak current ratings. NTC's are current limiters, not voltage limiters.
An NTC thermistor does its work in about .1 sec.
The GE CL Series of Current Limiters have thermal time constants measured in seconds. See the last column of their spec sheet.
The GE CL Series of Current Limiters have thermal time constants measured in seconds. See the last column of their spec sheet.
That's the thermal cycle time for the device to reset to its maximum cold state resistance, at an ambient temperature. The device is a variable resistor with variable voltages and currents attatched to variable amounts of capacitance. It's not the same time constant you calculate with a resistor and a cap. Read the rest of the data about the number of charge cycles the device typically protects. The device is not meant to throttle the PS for any longer than it needs to. It is at its lowest resistance very quickly which depends on the actual current it needs to restrict and the heat generated. But apart from that, do you think the device is really rated to handle 300v-400v or more from the typical B+ across it to an empty cap? What would the amperage be through it? Are the typical NTC's people use up to the maximum current that will pass through one from a high voltage source? They are generally used in all SS equipment from line voltage, not high voltage.
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Back to the begining. Go to Ametherm website. Look at sample circuits.Use the calculators. Done. If you do not want the sample device they will gladly send, do not ask for it. If you want to talk to someone who actually knows surge supression, call. But be aware that if you do you will almost certainly receive a box of samples and literature.
jhstewart9, if there was no inrush, the NTC has to be designed to heat up in temperature to a level where the NTC resistance is low enough not to significantly modulate with changing equipment current - ie. the equipment must present a minimum level of continuous current through the NTC.
The NTC must also survive a transient in-rush situation, where the current through it, and hence transient internal dissipation can get quite high as the bulk NTC temperature rapidly rises and resistance rapidly falls. Datasheets present that scenario as a level of capacitance that can be charged up for a given line voltage.
The application really needs to allow the NTC to cool back to ambient (reset) before it is asked to perform inrush protection again - hence the thermal time constant that is often more than a minute.
The design process for integrating an NTC in to anything other than a basic switchmode mains connection application does require a good awareness of how an NTC works, and just guessing at a suitable NTC part and what it will achieve can naively lead to poor outcomes.
The NTC must also survive a transient in-rush situation, where the current through it, and hence transient internal dissipation can get quite high as the bulk NTC temperature rapidly rises and resistance rapidly falls. Datasheets present that scenario as a level of capacitance that can be charged up for a given line voltage.
The application really needs to allow the NTC to cool back to ambient (reset) before it is asked to perform inrush protection again - hence the thermal time constant that is often more than a minute.
The design process for integrating an NTC in to anything other than a basic switchmode mains connection application does require a good awareness of how an NTC works, and just guessing at a suitable NTC part and what it will achieve can naively lead to poor outcomes.
I use a 1A 220R one for the B+. So far never had a problem. SL15 22101 Ametherm | Mouser
For main flicker protection, I use a manual reset GFCI Adapter. It saved me countless time after I saw a MC240 arcing during a flicking episode.
For main flicker protection, I use a manual reset GFCI Adapter. It saved me countless time after I saw a MC240 arcing during a flicking episode.
Is that somekind of power resistor that opens when heated by current?
I know of some devices that use a bimetallic strip whose deformation by heat shorts the resistor out.
I know of some devices that use a bimetallic strip whose deformation by heat shorts the resistor out.
I see no benefit to such a system wired that way.
As for an amp with EL84's, they really don't need any helping with delays.
They never did.
But internet driven paranoia seems to have expanded to thermistor use, along with unecessarily re-capping of things.
My EL84 amp's been in use since 2003 with all the same tubes, and still operates perfectly.
Are you scared of cathode stripping?
Maybe disconnecting the G2 grids until everything has been warmed up could help here. I have not tried it yet.....
BTW the Surgistor is in my little museum of rare items...
Maybe disconnecting the G2 grids until everything has been warmed up could help here. I have not tried it yet.....
BTW the Surgistor is in my little museum of rare items...
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I believe there are thousands of owners of push pull EL84 amplifiers that are made by Heathkit, Knight Kit, Dyna Kit, Scott, and others.
I would bet that most of them ran all those amplifiers for thousands of hours each, and never had a problem.
Now, things may be different. Quality of many parts is lower.
I never spent any nights worrying about the Knight Kit amps I used, and my friend never did either.
Lots of times, when the record changer returned the tone arm, I was already asleep.
The amp worked fine just waiting for me to turn it off the next morning.
Your mileage may vary.
And you probably are staying awake worrying about many other items in your house.
Just do not keep your all electric car in the garage, charging overnight.
Quality, Quality, Quality.
Not!
I would bet that most of them ran all those amplifiers for thousands of hours each, and never had a problem.
Now, things may be different. Quality of many parts is lower.
I never spent any nights worrying about the Knight Kit amps I used, and my friend never did either.
Lots of times, when the record changer returned the tone arm, I was already asleep.
The amp worked fine just waiting for me to turn it off the next morning.
Your mileage may vary.
And you probably are staying awake worrying about many other items in your house.
Just do not keep your all electric car in the garage, charging overnight.
Quality, Quality, Quality.
Not!
Cathode stripping?
Scared of what?
With EL64/6BQ5's lasting in a properly running amp I'm getting decades of use from them!
So again, all I read is about paranoid worries from numerous people about silly things.
I suppose the mind-control of the interent is to blame.
The main application for the Surgistor was in TV's, and that form of Surgistor was patented in 1959. For valve HiFi application, Heathkit advised its use as a service centre action for their W5M amp in the mid 1960's (about 10 years after the introduction of the W5M amp) due what appears to be related to the diy kit-build W5M power supply changes from earlier versions and the use of 3 PT manufacturers and hearsay of PT's running hot and internal potting cracking and a significant PT failure rate returning to Heathkit service centres.
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From the earliest W5M amplifiers, to the long term service support for the latest of the W5M amplifiers, something changed.
Yes, the power transformers changed, but . . .
. . . The Power Mains voltages went from 110V, to 115V, to 117V, to 120V.
That is hard on old power transformers.
Your Mains May Vary
Yes, the power transformers changed, but . . .
. . . The Power Mains voltages went from 110V, to 115V, to 117V, to 120V.
That is hard on old power transformers.
Your Mains May Vary