I would like to take some of this down time to learn more about my 2A3 SET amp circuitry. I figured it would make sense to start at the power supply. I have installed PSUD, and read through the article by DHTRob, but I don't have enough knowledge or experience to tackle this on my own.
Any experts out there willing to lend a hand?
Jim D
Any experts out there willing to lend a hand?
Jim D
Perhaps if you get PSUD2 installed, and read the help info, and make measurements needed to prepare the parameter values (especially for the transformer and choke), and get a screen grab up of what you've got and the queries you may have.
Search for other posts to see how others have progressed as well - Google search is a great mentor in itself.
Search for other posts to see how others have progressed as well - Google search is a great mentor in itself.
Your power supply schematic appears to be incorrect in that it does not show the negative (ground) leg coming from the center tap of the high voltage winding. Look at the schematic on this page.
5Y3, Tube 5Y3; Rohre 5Y3 ID3114, Full-Wave Vacuum Rectifier
I quickly came up with the following on PSUD. You will need to fine-tune some of the values such as the voltage of the transformer and the resistance of the choke as well as the milliamps for the current taps for the 2A3s and the 6SN7s.
I have not included the two 480 ohm resistors since I am not sure what role they play other than reducing the voltage.
I hope this helps.
ray
5Y3, Tube 5Y3; Rohre 5Y3 ID3114, Full-Wave Vacuum Rectifier
I quickly came up with the following on PSUD. You will need to fine-tune some of the values such as the voltage of the transformer and the resistance of the choke as well as the milliamps for the current taps for the 2A3s and the 6SN7s.
I have not included the two 480 ohm resistors since I am not sure what role they play other than reducing the voltage.
I hope this helps.
ray
Aside from no return on the rectifier, no ACV is noted for the HV winding. However there's more than enough data there to know where this is going. In fact a perfectly good answer can be got with a pencil on a 5Y3 datasheet.
I have no idea what "optimize" means here. The B+ is incredibly clean and the cost is unimportant.
A self-bias amp is NOT a "constant current". It is usually a lot closer to a resistor. That drawing shows the voltages, and thus the currents. Figure the effective resistance. 296V at 62mA is about 4735 Ohms.
I have no idea what "optimize" means here. The B+ is incredibly clean and the cost is unimportant.
A self-bias amp is NOT a "constant current". It is usually a lot closer to a resistor. That drawing shows the voltages, and thus the currents. Figure the effective resistance. 296V at 62mA is about 4735 Ohms.
Attachments
A few questions before I get into filling in more details:
When you speak of the AC voltage at the transformer, are you referring to the primary or secondary side?
How does the “return” for the center tap affect the circuit? The schematic reflects the actual wiring. The center tap wire is there, but (as far as I know) has never been connected.
Some back-story: These amps originated as George Wright WPA 3.5 amps. I bough them used used many years ago, and the previous owner had already done some mods. I believe these were primarily component upgrades vs circuit changes. I posted my schematic on Audio Asylum several years ago, and someone else with a stock version said it did not match his amp in some areas, but there have also been many comments that George Wright changed the circuit over the years, so it’s hard to tell what is “original”.
When I said I’d like to “optimize” the power supply, I meant that I would like to run my circuit in PSUD to see how it performs. Because the previous owner of these amps had changed the caps, I don’t know if they are the original values.
Thanks to everyone who has responded
More to come later...
When you speak of the AC voltage at the transformer, are you referring to the primary or secondary side?
How does the “return” for the center tap affect the circuit? The schematic reflects the actual wiring. The center tap wire is there, but (as far as I know) has never been connected.
Some back-story: These amps originated as George Wright WPA 3.5 amps. I bough them used used many years ago, and the previous owner had already done some mods. I believe these were primarily component upgrades vs circuit changes. I posted my schematic on Audio Asylum several years ago, and someone else with a stock version said it did not match his amp in some areas, but there have also been many comments that George Wright changed the circuit over the years, so it’s hard to tell what is “original”.
When I said I’d like to “optimize” the power supply, I meant that I would like to run my circuit in PSUD to see how it performs. Because the previous owner of these amps had changed the caps, I don’t know if they are the original values.
Thanks to everyone who has responded
More to come later...
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The power transformer HV winding feeds a full-wave rectifier - the CT of that winding needs to be identified and connected as PRR has shown.
Information is a bit ambiguous as the schematic shows measured voltage levels, but you don't say you made those measurements.
Given the possibility of circuitry problems, and changed parts, I would recommend the first step is to confirm correct operation or fault-find, using a variac and plug-in ss rectifier to avoid damaging parts and windings. Are you competent to fault-find such a HV power supply, and do you have servicing tools like a variac?
That first step would also gather the required power transformer info for PSUD (transformer secondary voltage, primary and secondary winding resistances, and choke resistance).
Information is a bit ambiguous as the schematic shows measured voltage levels, but you don't say you made those measurements.
Given the possibility of circuitry problems, and changed parts, I would recommend the first step is to confirm correct operation or fault-find, using a variac and plug-in ss rectifier to avoid damaging parts and windings. Are you competent to fault-find such a HV power supply, and do you have servicing tools like a variac?
That first step would also gather the required power transformer info for PSUD (transformer secondary voltage, primary and secondary winding resistances, and choke resistance).
Actually, the amps run fine and sound great. This is primarily a learning exercise for me, and a chance to fine-tune the amps if needed.
The voltages are from my measurements, and I do have most of the data in your last paragraph. I’ll add them to the schematic
The voltages are from my measurements, and I do have most of the data in your last paragraph. I’ll add them to the schematic
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