I have an amp project where I am going to use an indirectly heated dual damper tube as a slow start device. It has a max DC output of 175ma 6BY5GA.
https://frank.pocnet.net/sheets/127/6/6BY5G.pdf
Can I use it in a hybrid bridge or as a pass device with the plates in parallel? Which is "better"? Does option B with parallel plates increase the tubes max DC rating of 175ma or lessen its voltage drop over option A?
https://frank.pocnet.net/sheets/127/6/6BY5G.pdf
Can I use it in a hybrid bridge or as a pass device with the plates in parallel? Which is "better"? Does option B with parallel plates increase the tubes max DC rating of 175ma or lessen its voltage drop over option A?
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B is better. Lower VF drop, due to lower instantaneous current-per-anode. (minor unresolved issue… higher switching noise from silicon being in 'both phases'. ) … but the valve also works as a “snubber for free” ⋅-=≡ GoatGuy ✓ ≡=-⋅
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I reckon the rectifier switching behaviour would be controlled by the valve diodes in either option. It is the shape of the current pulse that matters, and both options have the rectifier current pulses passing through a valve diode.
The valve diode current specs still need to be respected for continuous peak, and hot turn-on surge. Given that the datasheet typically doesn't identify the latter limit, you may need to simulate it using something like PSUD2.
The valve diode current specs still need to be respected for continuous peak, and hot turn-on surge. Given that the datasheet typically doesn't identify the latter limit, you may need to simulate it using something like PSUD2.
If you use option B, you could dump the 6BY5 and use something like a 6CG3 instead if you need more peak/average current.
Yes I'm liking that even better, fewer moving parts, 350ma vs 175 of the 6BY5, nothing can get out of balance because just one cathode.
… if we had bacon, we could have bacon and eggs … if we had eggs.
The CG, remind yourself, is a Compactron tube. So, you have to get that 12 pin socket for your project. Not that this is a problem! It is a solid, durable rectifier. But my bit-of-humor kind of applies.
⋅-=≡ GoatGuy ✓ ≡=-⋅
The CG, remind yourself, is a Compactron tube. So, you have to get that 12 pin socket for your project. Not that this is a problem! It is a solid, durable rectifier. But my bit-of-humor kind of applies.
⋅-=≡ GoatGuy ✓ ≡=-⋅
I disagree with the terminology of calling (B) a hybrid rectifier. The rectification is happening in solid state.
The heater cathode insulation of damper diodes is also a lot higher than the 6BY5, so it's less likely that you need a separate heater winding.
Good point that term applies to option A only. In option B that tube can be identified as the chosen turn-on surge suppressor device?
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You may also move the damper diode to the negative rail . . . as well as the choke, if any 😉
Yves.
But the valve diode is imbuing a soft-start and soft-finish on each current pulse, applies a delayed and relatively slow power-on of the rectifier current pulses, and has a relatively large on-voltage - aspects that some want when they use just valve rectification, so imho calling it a hybrid is valid.
Similarly, the modern practise of adding a ss diode in series with each valve diode anode in a typical full-wave B+ supply circuit could be deemed a hybrid rectifier, as it imbues the robust PIV performance on a valve diode that will at some time fail from internal arcing and likely take out the power transformer secondary winding.
IMHO It's not a hybrid, because the tube isn't rectifying. It's just a pass device in scenario B.
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of course the tube is rectifying, everything is in series. If you want the tube not to be rectifying you need a rail cap after the ss bridge and before the tube. And that would be my recommendation too, let the robust SS bridge handle the first cap charging pulses, which SS diodes can do in their sleep. Let the tube be the slow warm up in series and provide a bit of series R which in combination with the next cap will further filter the B+