Long-time listener, first-time caller!
I'm new to this world and only have built a few kits, this is my first build from a schematic and the learning curve is steep.
I'm curious to hear what is the best practice for reducing the voltage of a power transformer's secondary. I'm adapting a Japanese tube preamp design to accommodate US AC power. I've found an Edcor transformer that will put out 18VAC @ 3A - I will wire two 9V secondaries in series - however, the circuit wants 15VAC @ 1.5A. What is the best way to achieve this? A voltage divider? Diodes?
And best practices for reducing the amperage on this and the other secondary... resistors?
I'm sure there are a bunch of approaches and any input would be appreciated.
Thanks!
I'm new to this world and only have built a few kits, this is my first build from a schematic and the learning curve is steep.
I'm curious to hear what is the best practice for reducing the voltage of a power transformer's secondary. I'm adapting a Japanese tube preamp design to accommodate US AC power. I've found an Edcor transformer that will put out 18VAC @ 3A - I will wire two 9V secondaries in series - however, the circuit wants 15VAC @ 1.5A. What is the best way to achieve this? A voltage divider? Diodes?
And best practices for reducing the amperage on this and the other secondary... resistors?
I'm sure there are a bunch of approaches and any input would be appreciated.
Thanks!
Post the schematic here. A tube preamp may be doable simply enough.
Oversizing the transformer in current rating may result in additional voltage to reduce.
Are you using the 250VAC winding as well?
Bear in mind these are dangerous voltages. Follow the proper guidelines accordingly.
Current rating is a maximum allowed, no need to do anything in that regard.
Oversizing the transformer in current rating may result in additional voltage to reduce.
Are you using the 250VAC winding as well?
Bear in mind these are dangerous voltages. Follow the proper guidelines accordingly.
Current rating is a maximum allowed, no need to do anything in that regard.
Thanks for the prompt reply. I appreciate the heads-up regarding dangerous voltages. I do feel comfortable around them but you can never be too safe! The preamp schematic is below. I will be using the 250VAC secondary as well even though it is slightly less than the 260VAC specified... this should be fine, no?
The 15Vac secondary only feeds the heaters. With an 18Vac secondary simply add additional 4 x 1ohm 5W resistors in series with the 1R 5W until you get back to near 13Vdc loaded at the 'output'. Additional 5W resistors rather than a single 5ohm are needed to dissipate the heat.
Took me a moment to get back to this! Thank you for the detailed response. I will start with several 1ohm 5W resistors and see what the voltage looks like. Wire wound should be fine, right? Two quick things...
Should I be trying to get the voltage down from 18V to 15V before the rectifier?
Also, do I have to worry about voltage fluctuation as the current is drawn, or is it relatively constant?
Thanks!
Should I be trying to get the voltage down from 18V to 15V before the rectifier?
Also, do I have to worry about voltage fluctuation as the current is drawn, or is it relatively constant?
Thanks!
