Salutations,
I have a question that may spark debate... I'm not referring to solid state vs. tube rectification.
Is there any benefit to using transmitting rectifiers, such as the 836, vs, using TV dampers?
The only benefit I see is TV dampers are limited in voltage for rectifier service, so I'm guessing the transmitter rectifiers may be better suited for high secondary voltages...is this accurate?
All comments are welcome
Roger
I have a question that may spark debate... I'm not referring to solid state vs. tube rectification.
Is there any benefit to using transmitting rectifiers, such as the 836, vs, using TV dampers?
The only benefit I see is TV dampers are limited in voltage for rectifier service, so I'm guessing the transmitter rectifiers may be better suited for high secondary voltages...is this accurate?
All comments are welcome
Roger
Damper diodes outperform those old TX rectifiers by a pretty wide margin in forward voltage loss, and their inverse plate voltage rating isn't shabby. Some folks will want 836s just for sex appeal, of course.
Damper diodes "limited in voltage" ? Are you building a x-mitter ?
6DW4B damper diode characteristics:
P.I.V : 5.500 volts (vs 5.000 volts for the 836)
Peak Plate Current: 1.3A (vs 1A for the 836)
Both are half wave (single plate) diodes and (color TV) dampers are much cheaper and readily available. I can't see any benefits ,except (maybe) for the looks.
6DW4B damper diode characteristics:
P.I.V : 5.500 volts (vs 5.000 volts for the 836)
Peak Plate Current: 1.3A (vs 1A for the 836)
Both are half wave (single plate) diodes and (color TV) dampers are much cheaper and readily available. I can't see any benefits ,except (maybe) for the looks.
I was referring to Damper TV tubes being rated differently for mains rectification...
Per blog from VinylSavor
"The original version 6BY5G was rated at a peak inverse voltage of 2500V. This rating is for TV damper service only. The Tung-Sol datasheet also states the peak inverse voltage for mains rectifier service at 1400V. "
VinylSavor: Tube of the Month: The 6BY5
And Datasheet (thank you Frank) http://www.mif.pg.gda.pl/homepages/frank/sheets/127/6/6BY5G.pdf
If I apply the similar derating from the toughest "octal base" damper I know...but tell no one...keep prices low...
6DT4- http://www.nj7p.org/Tubes/PDFs/Frank/127/6DT4.pdf
Then 5500V should be around 3080V...which is more than enough.
I have also heard that dampers need to run at near maximum to be safe... However I do understand the oceans of misinformation on the web while finding the islands of truths.
I just hope I'm on the right path...Safety, design, design, simulate, simulate, safety, safety, some aesthetic flare, then build and listen, check safety...listen, tweek, listen.
Also, using the 836 opens doors to control voltage output by using different rectifier tubes.... the 1616 can be used to drop the B+ significantly, while the 3B28 can be used to increase B+.
I build the power supply to withstand more than the Secondary V x 1.414, thus when voltage comes on with zero load...no fireworks from the caps.
Per blog from VinylSavor
"The original version 6BY5G was rated at a peak inverse voltage of 2500V. This rating is for TV damper service only. The Tung-Sol datasheet also states the peak inverse voltage for mains rectifier service at 1400V. "
VinylSavor: Tube of the Month: The 6BY5
And Datasheet (thank you Frank) http://www.mif.pg.gda.pl/homepages/frank/sheets/127/6/6BY5G.pdf
If I apply the similar derating from the toughest "octal base" damper I know...but tell no one...keep prices low...
6DT4- http://www.nj7p.org/Tubes/PDFs/Frank/127/6DT4.pdf
Then 5500V should be around 3080V...which is more than enough.
I have also heard that dampers need to run at near maximum to be safe... However I do understand the oceans of misinformation on the web while finding the islands of truths.
I just hope I'm on the right path...Safety, design, design, simulate, simulate, safety, safety, some aesthetic flare, then build and listen, check safety...listen, tweek, listen.
Also, using the 836 opens doors to control voltage output by using different rectifier tubes.... the 1616 can be used to drop the B+ significantly, while the 3B28 can be used to increase B+.
I build the power supply to withstand more than the Secondary V x 1.414, thus when voltage comes on with zero load...no fireworks from the caps.
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I'm aware of the derating issues but have used TV dampers in many (50/60 c/s) mains supply rectification applications and never had any reliability issues, they're actually very rugged tubes. If you look into old ARRL handbooks you'll find many circuits using TV dampers in H.V transmitter power supplies. Also, I can't see any (technically valid) reason why they should be operated "near maximum ratings to be safe". Also, TV dampers have indirectly heated cathodes (a built-in slow start-up feature) and (unlike the 836) doesn't need pre-heating and delayed application of plate voltage. (this latter feature could hardly be considered as an advantage).
I find most ( all ?) tv-dampers with a very good isolation between filament and cathode, so
good that you won't need a separate filament winding.
good that you won't need a separate filament winding.
Is this thread about primary side mains rectification, or secondary side with a highish VAC?
Over 550-600VAC secondary side, the common valve diode datasheets run out for choke (and cap at lower current) input filtering.
What path are you trying to take, and why?
Over 550-600VAC secondary side, the common valve diode datasheets run out for choke (and cap at lower current) input filtering.
What path are you trying to take, and why?
Thanks Tublogic- The 836 is indirectly heated with the cathodes connected to the heater internally.
Trobbins- This thread pertains to the secondary voltage for the B+.
I am making an amp that uses b+ of 650V-750V+ so I can maintain a 575V+ plate voltage for KT88 and possibly other power tubes/ transmitting tubes.
I'm looking at using High Volts at low mA with high impedance output transformers. Over 10k impedance. This keeps the 3rd order harmonics down, even though it increases 2nd order.
So, current ratings aren't a real issue...voltage ratings are. The current draw will be around 100-120mA draw for the entire amp.
If I use an 836 and high voltage doesn't work out, I can put in a 1616 to drop the voltage.
The power supply will be filtered with CLC with 400V Capacitors stacked 3x to handle 1200VDC. Smaller caps values will be used and paralleled, so each one will store less energy. Bleeder balancing resistors will be used...which acts as bleeders as well.
I know this amp and my methods will be questioned...but the parts, materials and construction have been thoroughly researched. My research consists of not only audio sites but engineering sites, calls and data sheets as well.
I will start another thread about the amp.
Trobbins- This thread pertains to the secondary voltage for the B+.
I am making an amp that uses b+ of 650V-750V+ so I can maintain a 575V+ plate voltage for KT88 and possibly other power tubes/ transmitting tubes.
I'm looking at using High Volts at low mA with high impedance output transformers. Over 10k impedance. This keeps the 3rd order harmonics down, even though it increases 2nd order.
So, current ratings aren't a real issue...voltage ratings are. The current draw will be around 100-120mA draw for the entire amp.
If I use an 836 and high voltage doesn't work out, I can put in a 1616 to drop the voltage.
The power supply will be filtered with CLC with 400V Capacitors stacked 3x to handle 1200VDC. Smaller caps values will be used and paralleled, so each one will store less energy. Bleeder balancing resistors will be used...which acts as bleeders as well.
I know this amp and my methods will be questioned...but the parts, materials and construction have been thoroughly researched. My research consists of not only audio sites but engineering sites, calls and data sheets as well.
I will start another thread about the amp.
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Wouldn't a 600VAC secondary provide the B+ you are after? I'd suggest a common rectifier tube with 1600-1800V piv would then suit with capacitor input filter.
650-0-650VAC secondary goes above the 5R4/5AR4 600VAC max rating, so I think you are above the range of most commonly used dual diode tubes.
I can recommend a modern sneak-around method, that is now often used to make amps with common valve diodes more bullet-proof. Adding series ss diodes with each anode of a common dual diode tube is very effective at raising the PIV of the tube. The ss diode is typically a 1N4007, as there is no need for reverse recovery concern (the tube still makes the turn-off relatively soft and with no reverse recovery effect). Above about 300-0-300VAC secondaries, at least 2 ss diodes in series are needed to achieve an acceptable ss PIV (in case the valve diode has degraded and provides effectively no PIV), and those 2 diodes need to be from the same batch to provide confidence that they will nominally share PIV, plus have a substantial margin for poor sharing.
Given your 650-0-650VAC secondary, I could suggest 3x 1N4007 in series with each diode of any common dual diode, such as 5U4 direct heat or 5V4 indirect heat.
This is just a convenient alternative to what you were originally proposing. PSUD2 would still be needed to confirm that your expected filter design kept hot turn-on and normal max continuous diode current levels within datasheet limits. You could still likely use 250VAC rated fuses for the secondary winding protecting, as although their application is allowed at higher VAC, 650VAC is likely to be still at the limits of that territory.
Ciao, Tim
I can recommend a modern sneak-around method, that is now often used to make amps with common valve diodes more bullet-proof. Adding series ss diodes with each anode of a common dual diode tube is very effective at raising the PIV of the tube. The ss diode is typically a 1N4007, as there is no need for reverse recovery concern (the tube still makes the turn-off relatively soft and with no reverse recovery effect). Above about 300-0-300VAC secondaries, at least 2 ss diodes in series are needed to achieve an acceptable ss PIV (in case the valve diode has degraded and provides effectively no PIV), and those 2 diodes need to be from the same batch to provide confidence that they will nominally share PIV, plus have a substantial margin for poor sharing.
Given your 650-0-650VAC secondary, I could suggest 3x 1N4007 in series with each diode of any common dual diode, such as 5U4 direct heat or 5V4 indirect heat.
This is just a convenient alternative to what you were originally proposing. PSUD2 would still be needed to confirm that your expected filter design kept hot turn-on and normal max continuous diode current levels within datasheet limits. You could still likely use 250VAC rated fuses for the secondary winding protecting, as although their application is allowed at higher VAC, 650VAC is likely to be still at the limits of that territory.
Ciao, Tim
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Thank you for all your comments and ideas.
If I use solid state, I will go all solid state rectification.
I also have transformers that are 230V primary with dual 6V secondary. I'm on 120V USA power which makes these transformers a little over 3V...dual secondary 4.5A... just in range for the heaters for a couple 3DG4's for a voltage doubler. I'm sure it can handle some caps in the 30uf - 82uf range. Remember...I only need about 120mA total. I also have a 4 0B2's and 2 0A2's I could use for regulation.
If I use solid state, I will go all solid state rectification.
I also have transformers that are 230V primary with dual 6V secondary. I'm on 120V USA power which makes these transformers a little over 3V...dual secondary 4.5A... just in range for the heaters for a couple 3DG4's for a voltage doubler. I'm sure it can handle some caps in the 30uf - 82uf range. Remember...I only need about 120mA total. I also have a 4 0B2's and 2 0A2's I could use for regulation.
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