Hi All.
I would like create two separate power supplies on one chassis using two power transformers and two filament transformers. My question is whether or not it is possible or advisable to use one filament transformer to power the four 5AR4 rectifiers used on both supplies, and use the other filament transformer to power the four 6AS7 and two EF86 used in both supplies. I have attached photos of the transformer specs as printed on the transformers, and of the proposed power supply layout. Can the filaments of all the 5AR4s be connected to one of the filament transformers, while two of them are used to rectify the AC of one power transformer, and the other two are used to rectify the AC of the other power transformer? Ditto for the 6AS7s? There is another smaller winding that I can use for each of the EF86. Alternately, can I run the rectifiers (with a voltage dropping resistor) and the 6AS7 pass tubes on the same winding? The power supply is the one from Thorsten Loesch's Legacy 300B amp. I have attached the schematic of the power supply as well. Any advice and guidance would be much appreciated.
Cheers, Tiz
I would like create two separate power supplies on one chassis using two power transformers and two filament transformers. My question is whether or not it is possible or advisable to use one filament transformer to power the four 5AR4 rectifiers used on both supplies, and use the other filament transformer to power the four 6AS7 and two EF86 used in both supplies. I have attached photos of the transformer specs as printed on the transformers, and of the proposed power supply layout. Can the filaments of all the 5AR4s be connected to one of the filament transformers, while two of them are used to rectify the AC of one power transformer, and the other two are used to rectify the AC of the other power transformer? Ditto for the 6AS7s? There is another smaller winding that I can use for each of the EF86. Alternately, can I run the rectifiers (with a voltage dropping resistor) and the 6AS7 pass tubes on the same winding? The power supply is the one from Thorsten Loesch's Legacy 300B amp. I have attached the schematic of the power supply as well. Any advice and guidance would be much appreciated.
Cheers, Tiz
I understand that this is a weird situation with a weird set of questions, so I'll try be more clear. I want to use two power transformers and two filament transformers on one chassis. The power from each power transformer will feed two rectifiers in parallel, and then two pass tubes and an EF86 as shown in the schematic above. Basically, I'm asking if there are any issues with two power supplies sharing one large filament transformer for the rectifiers, and another large filament transformer for all the other tubes. Please see my attached drawing that shows what I would like to do with the rectifiers. I would like to do the same for all the pass tube and EF86 heaters.
1. Can I use a single filament transformer for all the pass and voltage reference tubes for both supplies?
2. Can I use a single filament transformer for all four rectifiers in both supplies?
3. Is there a better way to do this using the two power transformers and the two filament transformers in order to create two separate power supplies?
?
1. Can I use a single filament transformer for all the pass and voltage reference tubes for both supplies?
2. Can I use a single filament transformer for all four rectifiers in both supplies?
3. Is there a better way to do this using the two power transformers and the two filament transformers in order to create two separate power supplies?
Are there any dual-diode rectifiers that don't have their cathodes connected to filaments internally?
All good fortune,
Chris
All good fortune,
Chris
Your filament transformer is only rated for 300VAC from ground, and it'll see B+ as a heater transformer for the GZ34. And it's the wrong voltage. 6.3V vs 5V
6BY5 is the only one I know of.
kodabmx:
Thanks for your reply. I was considering using a dropping resistor as per the Legacy schematic. If only 6BY5 will work, there is no point. I was trying to be cheap, as I have a number of the 6.3 (12.6) volt transformers on hand. I will order a couple of these 5 volt transformers, one per supply, if they are appropriate...
https://www.digikey.ca/en/products/detail/hammond-manufacturing/166RS/455153
Or maybe these...
https://www.digikey.ca/en/products/detail/hammond-manufacturing/167R5/455258
Am I okay using just one of the filament transformers that I have on hand (pictured above) for all the 6.3 volt tubes on both power supplies?
Hi Chris. Thanks for your reply. My intention was to use the 5AR4s that are in the Legacy schematic. I thought that because the 5AR4 is indirectly heated, it had a separate cathode and filament, but that is not the case.
1.) You want to use (four) series connected filaments ????
Rather I would use two parallel connected (5V) filament per PSU. The required current in this case is -at least- 4A, rather 5A per PSU, so two 5V/4..5A filament transformer is need.
2.) 5AR4 filament is internally connected to its cathode, so filament potential is on the rectified high (more than 540V) voltage. If you use one or two rectifier per PSU, it's OK (if you use appropriate filament transformer), but never tie together individual PSU filaments!
Rather I would use two parallel connected (5V) filament per PSU. The required current in this case is -at least- 4A, rather 5A per PSU, so two 5V/4..5A filament transformer is need.
2.) 5AR4 filament is internally connected to its cathode, so filament potential is on the rectified high (more than 540V) voltage. If you use one or two rectifier per PSU, it's OK (if you use appropriate filament transformer), but never tie together individual PSU filaments!
You may be able to use four TV damper diodes in place of the 5AR4s. Modern 5AR4s are crap on a crust anyway, and 500VAC is way into danger territory. Damper diodes are designed to have their cathodes at high peak voltages ref. the heaters, but if you have the windings enough, you could elevate their heaters up near B+. How are you fixed for 6.3VAC/maybe 3 to 6 Amps times two?
All good fortune,
Chris
All good fortune,
Chris
If I do use 5AR4, I will purchase two 5 volt filament transformers, but Chris reminded me of damper diodes, which I completely forgot about.
Thanks for the reminder about damper diodes. I have never used them, but I think I have plenty of them and the required 6.3 volt transformers to power them. I have five of the 6.3 volt transformers in the photo above. I’ll have to check on the types of damper diodes I have. Which ones would you suggest?
A 500V-0-500Vrms windings = 707V peak at each rectifier plate.
You are talking about a very serious power supply.
Such power supplies will not work if everything is at maximum capability, or beyond maximum capability.
You are beyond maximum capability.
1. If you use a rectifier that drops 50V, that means the plates of the 6AS7 tubes will be 707V - 50V = 657V peak. Many rectifiers have more like a 25V or 35V drop (not 50V drop). Remember, rectifier voltage drop is listed when the rectifier is loaded.
Wow, you are using 22uF caps after the rectifier that are only rated for 630V.
If the B+ load is not there (either cold output tube filaments/cathodes at power-up, or output tube failures, the B+ will go to +657VDC.
2. If the B+ is ever un-loaded, the Peak Reverse volts from rectifier cathode to plate is +657VDC from the 22uF capacitors, and another 657V peak from the rectifier plate.
That is a Peak Inverse Voltage of 1,314V.
Watch out for the rectifier ratings, capacitor ratings, 6AS7 ratings, EF86 ratings, etc.
3. 300V maximum cathode to filament voltage 6SA7; your cathodes are at +420V
50V maximum filament to cathode voltage EF86; your cathode is at +80V.
Are you going to elevate the 6.3V filament to +50 +80VDC (+130VDC), then the EF86 is at maximum, and the 6AS7 cathode is within 10V of maximum rating.
What happens if the B+ is unloaded (examples above). Those ratings will be exceeded, because the 500-0-500 volt of the power transformer secondary is when it has a load, without a load it is more than 500Vrms and more than 707Vpeak.
That is a serious power supply that will require some real work to get things to be within parts specifications, and reliably working.
There is no easy and cheap way to get that power supply reliably up and running.
Your Mileage May Vary.
Just my opinions
You are talking about a very serious power supply.
Such power supplies will not work if everything is at maximum capability, or beyond maximum capability.
You are beyond maximum capability.
1. If you use a rectifier that drops 50V, that means the plates of the 6AS7 tubes will be 707V - 50V = 657V peak. Many rectifiers have more like a 25V or 35V drop (not 50V drop). Remember, rectifier voltage drop is listed when the rectifier is loaded.
Wow, you are using 22uF caps after the rectifier that are only rated for 630V.
If the B+ load is not there (either cold output tube filaments/cathodes at power-up, or output tube failures, the B+ will go to +657VDC.
2. If the B+ is ever un-loaded, the Peak Reverse volts from rectifier cathode to plate is +657VDC from the 22uF capacitors, and another 657V peak from the rectifier plate.
That is a Peak Inverse Voltage of 1,314V.
Watch out for the rectifier ratings, capacitor ratings, 6AS7 ratings, EF86 ratings, etc.
3. 300V maximum cathode to filament voltage 6SA7; your cathodes are at +420V
50V maximum filament to cathode voltage EF86; your cathode is at +80V.
Are you going to elevate the 6.3V filament to +50 +80VDC (+130VDC), then the EF86 is at maximum, and the 6AS7 cathode is within 10V of maximum rating.
What happens if the B+ is unloaded (examples above). Those ratings will be exceeded, because the 500-0-500 volt of the power transformer secondary is when it has a load, without a load it is more than 500Vrms and more than 707Vpeak.
That is a serious power supply that will require some real work to get things to be within parts specifications, and reliably working.
There is no easy and cheap way to get that power supply reliably up and running.
Your Mileage May Vary.
Just my opinions
6D22S x 4 would kick donkey.
6V3 1.9A each. Capable of 300mA continuous with peaks up to 1 ampere - half wave but you were going to use 4 tubes anyway...
Caveat is the cathode cap. Some people don't like tubes with a cap.
6V3 1.9A each. Capable of 300mA continuous with peaks up to 1 ampere - half wave but you were going to use 4 tubes anyway...
Caveat is the cathode cap. Some people don't like tubes with a cap.
Looks like two of your mil-surp Freeds could do the job. One for the rectifiers, if each of their heaters draws 2.75A or less, biased up maybe 300-400VDC above ground. The other for the pass valves (2x 5A per half of the 12.6VAC) and control valve (6.3VAC), each biased up near their cathode voltages.
You may want to consider some effort to stage these, and the HV transformers, and load filament power, over time. I worry that the pass valves might not take a steady diet of potentially 700VDC turn-ons, worst case. Type 6D22S has an extremely slow warmup, and that could be enough for normal turn-ons, leaving only hot-switching as an issue. And bleeders!
Although, the conflicting diagrams and photos are very ambiguous. How many total pass valves?
All good fortune,
Chris
You may want to consider some effort to stage these, and the HV transformers, and load filament power, over time. I worry that the pass valves might not take a steady diet of potentially 700VDC turn-ons, worst case. Type 6D22S has an extremely slow warmup, and that could be enough for normal turn-ons, leaving only hot-switching as an issue. And bleeders!
Although, the conflicting diagrams and photos are very ambiguous. How many total pass valves?
All good fortune,
Chris
Thanks for your input. The power supply pictured above is from Thorsten Loesch's Legacy 300B amp. He does not show any elevation of filaments whatsoever. I know of two builds of this amp, one of which is partially documented in these forums. I'll try to contact the builder to see if there was any issues with the amp built as per this schematic. The caps I have for this amp are rated at 700 volts.
Chris: I have attached screenshots of the entire schematic for clarity. The power supply for the amp has two 5AR4, two 6AS7, and one EF86. I was hoping to build two full power supplies and have them share a single chassis. At this point, it seems easier to just build each supply on its own chassis. The schematic not addressing the need for elevating the heaters in this power supply seems a gross oversight, to put it mildly. The caps shown in the schematic are rated at 630 Volts. The ones I have on hand are rated at 700 Volts. What would a staged turn on look like? Would using 5AR4 or 6D22S provide that staged turn on?
Oops! Here are the screenshots....
I don't see any elevation of heaters in this schematic. This seems like a gross oversight for someone like Loesch, who has always seemed both astute and knowledgeable to me. I don't get it.
I'm still confused. That B+ supply is more than big enough for two 300B amplifiers, with their drivers. Was that the original purpose? If so, and you're wanting to divide it in halves, one half for each channel, you'll only need half the number of rectifier valves and half the number of pass valves. The rest stays the same.
Looks like you have two plate transformers, and plenty of heater transformers, so, with 6.3V damper diodes as rectifiers, you're cookin'. The 12.6VAC winding of each filament transformer needs to be biased up very near the pass valves' cathode voltage, maybe connected with a resistor. This should be safe to use for two rectifier heaters on one half and two pass valves' heaters on the other half. Control valve heater on the 6.3VAC winding, biased up near or slightly above its cathode voltage.
All good fortune,
Chris
Looks like you have two plate transformers, and plenty of heater transformers, so, with 6.3V damper diodes as rectifiers, you're cookin'. The 12.6VAC winding of each filament transformer needs to be biased up very near the pass valves' cathode voltage, maybe connected with a resistor. This should be safe to use for two rectifier heaters on one half and two pass valves' heaters on the other half. Control valve heater on the 6.3VAC winding, biased up near or slightly above its cathode voltage.
All good fortune,
Chris
Chris: the intention was to use the double power supply to supply a 300B amp and a
45 amp that will power a two way speaker. Also, I want to build a pair of choke input power supplies that will have a lower B+ output. I may use the supplies discussed in this thread to power a channel each of the 300B amp, and the choke loaded supplies to power a channel each of the 45 amp. I may also power the pre tubes and the power tubes separately of one amplifier. Ultimately, I am hoping to end up with four supplies that I can use in different ways for different amplifiers, that will power a two way and a horn sub.
45 amp that will power a two way speaker. Also, I want to build a pair of choke input power supplies that will have a lower B+ output. I may use the supplies discussed in this thread to power a channel each of the 300B amp, and the choke loaded supplies to power a channel each of the 45 amp. I may also power the pre tubes and the power tubes separately of one amplifier. Ultimately, I am hoping to end up with four supplies that I can use in different ways for different amplifiers, that will power a two way and a horn sub.
Chris: the intention was to use the double power supply to supply a 300B amp and a 45 amp that will power a two way speaker. Also, I want to build a pair of choke input power supplies that will have a lower B+ output. I may use the supplies discussed in this thread to power a channel each of the 300B amp, and the choke loaded supplies to power a channel each of the 45 amp. I may also power the pre tubes and the power tubes separately of one amplifier. Ultimately, I am hoping to end up with four supplies that I can use in different ways for different amplifiers.