Wavebourn,
I could not have 'Swung' a better answer myself.
Pity the person that uses the Wrong choke, and some Mercury Rectifiers.
I could not have 'Swung' a better answer myself.
Pity the person that uses the Wrong choke, and some Mercury Rectifiers.
Are you saying filaments and B+ should go on at the same time? That would certainly destroy the tubes in this amp. What's your suggestion, my friend?
Thanks for this interesting result. The choke in this amp has always been the main problem. I have actually tried different chokes in the past and they were all extremely noisy. I remember spending quite some money in 3 or 4 different chokes, but they were all specified for 400mA. But that was over 10 years ago.I think the guy who designed the amp didn't want to make a bigger choke to deal with the inrush current and was counting on the delay/resistor to cure that problem. The choke gap calculation was also a huge issue. My experience with this was very frustrating and if I have to go after a new choke for the amp I'll probably put the amp back in storage.
(I have actually measured the choke with an inductance meter and it reads 4.7 instead of 5H... Maybe the meter is not accurate, but chances are that the saturation is even higher and that that choke would need to be even larger!)
What about the idea of using two switches: one for a 100ohm resistor and another for the full power? I can trow the first switch a few seconds after the filaments are hot... I have done some tests and I saw not arc.
Waveborn, what do you think?
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chokes for choke input filters are often noisy. Putting a small cap before the choke can help a lot. I also soaked one of mine in a plastic bag of varnish, left it to warm in the sun and then harden for several days - that also made a big difference.
Yes he is. And why would it destroy the tubes ?
Yes he is. And why would it destroy the tubes ?
Wait, now I'm confused. Weren't I complaining about the spark in the tube happening even with a delay and even with a 100R? Weren't you and the others confirming that the arc would be bad news for that tube? Well, activating the HV at the same time as the filaments would be far worse than that. I have tested today switching the HV a few seconds after the filaments and the blue spark in the tube was much bigger.
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I'd say that's a good place to start - use high voltage film cap as the peak voltages at this point will be nasty.
I suspect that the reason for the arcing is not because of the sudden application of B+ but because the circuit is over-stressing the tube rectifiers. These rectifiers are likely now toast and can't be rescued so get some test mules at low cost to debug this with - if you want slow start go with 5AR4 types. Then try the remedies suggested - small capacitor before the choke (will also help with hum). Try SS diodes in series with the plates. See if this helps before worrying about adding series resistance. Additional series resistance will help with the charging up of the large capacitors after the choke. In a way, the 100R on the primary serves this purpose already since it's impedance is reflected to the secondary by the turns ratio so you can tweak that higher if need be.
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Vice verse my friend, vice verse. What causes arching in your amp, sudden high current through your rectifier. Your choke most probably is wrong and saturates, the filter capacitor has too high value for such choke, plus delayed B+ causes huge current spike through output tubes when B+ is applied. What I am suggesting, to follow laws of physics instead of opinions that you have read somewhere and mixed together.
Do we agree that there's no arc or spark of any sort going on the o/p tubes and the only arc happening is on the rectifiers? can the huge current spikes in the o/p tubes be invisible?
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As we can't see your output tubes it's hard to agree what's going inside them - I suspect nothing bad is going with the output tubes - the excitement is all inside the rectifiers
Sure they are invisible, that's why there are still lot of amps made and sold with B+ delay relays where output tubes do not arc. They just create extra inrush current, that's it. And probably die younger, due to control grid currents every time the amp is powered on.
fireworks 😀
If the HV with the 100R (or larger) is turned on with the filaments, would that be enough to avoid the o/p tube current spike you're talking about?
I usually insert inrush current limiting resistor in series with the primary. But I never use vacuum tube rectifiers, so all voltages in the secondaries ramp up with the same speed. As soon as one of them, usually DC filament voltage is enough to engage the relay, it shunts the resistor in primary. Such a way I prolong lives of tubes, save fuses, and avoid dimming of house lights when I power on one of my amps, like 45W/CH SE Gubernator-71, 100W/Ch PP Pyramid-VII, or 100W/Ch Tower-VII that consumes more than kilowatt constantly.
Instead of a resistor can be used a thermistor, but it is not necessary, since the relay anyway shunts it when it's done.
Wavebourn - Inrush current limiter, +400 and +800V... | Facebook
Instead of a resistor can be used a thermistor, but it is not necessary, since the relay anyway shunts it when it's done.
Wavebourn - Inrush current limiter, +400 and +800V... | Facebook
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Instead of living in California you should move north where electric heaters are more common 😛
Who said you that I run it? I made it as an exercise, for those who has Magnepans. 😀
I am listening to 6W/Ch Edelweiss-3, with 92 dB/WM JBL monitors. Sweet! 🙂
Wavebourn - Edelweiss-3 with 6CB5A output tubes | Facebook
I am listening to 6W/Ch Edelweiss-3, with 92 dB/WM JBL monitors. Sweet! 🙂
Wavebourn - Edelweiss-3 with 6CB5A output tubes | Facebook
Maybe I'm missing something from what you've been saying, but isn't what you're doing very similar to the scheme I have? I have a transformer for the filaments (check my first post) and another one for the HV. There's a 100R inrush current limiting in series with the primary of the HV transformer which is shunt after a few seconds by a relay. The relay is part of a delay, which you claimed should never be present in an amplifier.
OK, I understand you're not using a delay per se, but I wonder how different what you're doing is from this... The problem I'm having – which might as well, as you said, be related before anything to a inadequate inductor, caps, etc.– is that regardless of that 100R, I see a small arc in the regulators when voltage to the filaments and the 100R is applied (so before the full HV kicks in). As Bigun suggested, perhaps all I need is to increase the 100R and try the things suggested here (small cap and diodes in series with filament's) to solve the issue. You brought the issue of the huge current spikes on o/p tubes when HV is delayed. May I assume then you were not considering the specific scheme I have, ie with te 100R in place, etc?
Spartan, you prepared a PSUD schematic in post #17.
How did you determine the transformer parameters?
Did you measure the transformer winding resistances and voltages?
Do the transformer and chokes have manufacturer and model numbers?
Do the capacitors have 10mohm ESR?
Did you measure the choke DCRs?
Have you also set the simulation up for the 'power-on' situation, with no reporting delay or soft-start, and no circuit loading, as that is when the arcing occurs?
How did you determine the transformer parameters?
Did you measure the transformer winding resistances and voltages?
Do the transformer and chokes have manufacturer and model numbers?
Do the capacitors have 10mohm ESR?
Did you measure the choke DCRs?
Have you also set the simulation up for the 'power-on' situation, with no reporting delay or soft-start, and no circuit loading, as that is when the arcing occurs?
I didn't prepare anything. I have made that many years ago, as I said above, and the information I used at the time was mostly from measuring with a multimeter.
Ok, you prepared a PSUD schematic and 'posted' it in post #17, but don't really recall how you arrived at some of the values.
Whether you want to investigate diode PIV stress, or transformer in-rush (with or without series resistance in mains), or almost anything else related to why a valve diode may arc, then I'd highly recommend you spend your time to gather information on your parts first.
That may save a few new threads and many new posts, as you make new suggestions on what you think is the cause of the arcing and what could be the silver bullet solution.
Whether you want to investigate diode PIV stress, or transformer in-rush (with or without series resistance in mains), or almost anything else related to why a valve diode may arc, then I'd highly recommend you spend your time to gather information on your parts first.
That may save a few new threads and many new posts, as you make new suggestions on what you think is the cause of the arcing and what could be the silver bullet solution.
To your question: Have you also set the simulation up for the 'power-on' situation, with no reporting delay or soft-start, and no circuit loading, as that is when the arcing occurs?, I really don't remember.
The other info you ask about is mostly stated in that simulation and they were, again, taken with a multimeter.
The other info you ask about is mostly stated in that simulation and they were, again, taken with a multimeter.
Maybe its a good time to double check the transformer primary and secondary winding resistances, to confirm you calculated the effective resistance correctly. Your hand-drawn sketch shows 630V, and PSUD2 shows 674V - is 674V the unloaded voltage or the voltage with your amp on and settled?
Do the choke parts have a manufacturer and model? If not then how did you measure choke inductance?
What brand and voltage rating caps are you using?
Do the choke parts have a manufacturer and model? If not then how did you measure choke inductance?
What brand and voltage rating caps are you using?
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