I thought a centre tapped transformer was like 25-0-25 (3 lines).
What I have is 25-0, 25-0 (4 lines)
Really, two diodes? I am surprised.
What I have is 25-0, 25-0 (4 lines)
Really, two diodes? I am surprised.
Two diodes and centre tap, all time classic. Its as full wave as a bridge, only wastes secondary turns. Which you have. Just check all valve rectified HV PSU, they work like that. Using your middle wires together and connecting to the central input of the ACin connector would work.
Awesome! 
Well, I've learned something, which isn't hard considering the chasm between your electronics skills and mine 
What a dude, spending half your life on here sharing your knowledge with
s like me. 
Well, I've learned something, which isn't hard considering the chasm between your electronics skills and mine What a dude, spending half your life on here sharing your knowledge with
s like me.
Eureka! (as I believe a fellow countryman of yours once said). It works! Thanks for that.
Joan Jett eh? Hot rockin' badass bitch that one!
Joan Jett eh? Hot rockin' badass bitch that one!
I am aiming for 30v DC out now, as Mads K suggests 27v is nominal and 30v will give greater headroom.
I am a little confused by a lot of the instructions. Terms like Vbe, Rset, Vref, ICCS etc.
It's all Greek to me! 🙂 I will muddle through....
I am a little confused by a lot of the instructions. Terms like Vbe, Rset, Vref, ICCS etc.
It's all Greek to me! 🙂 I will muddle through....
Vbe= Voltage from base to emitter of a transistor
ICCS = I (current) of a Constant Current Source (or Sink)
Vref = Voltage of a reference
Rset = Resistance(resistor) setting, probably a variable resistor or R that sets a value elsewhere.
ICCS = I (current) of a Constant Current Source (or Sink)
Vref = Voltage of a reference
Rset = Resistance(resistor) setting, probably a variable resistor or R that sets a value elsewhere.
you might be struggling to get a regulated 30Vdc from a 25Vac transformer.
If it is a 230:25+25Vac and you use it on a UK 240Vac supply there is a better chance the regulator won't drop out.
It is 230v. Thanks
before the European Harmonisation of supply voltage, the UK had a nominal 240Vac distribution system. The tolerance on voltage was +-6%.
Then the EC took over and said we all had to have the same appliances run from the same voltage.
The UK adopted a 230Vac +~10% and -~6% giving 216Vac to 254Vac as the range of normal supply voltage.
But we didn't actually change our nominal supply voltage, the generating plant and the transmission system remained the same. The UK is still a 240Vac country that still operationally works on +-6%, but the specification allows 216Vac as our bottom limit rather than 226Vac.
Your minimum voltage for normal supply is 226Vac into your 230Vac transformer.
Your maximum voltage for normal supply is 254Vac into your 230Vac transformer. Using the regulation of the transformer, you can now determine the worst case range of secondary output voltages.
Then the EC took over and said we all had to have the same appliances run from the same voltage.
The UK adopted a 230Vac +~10% and -~6% giving 216Vac to 254Vac as the range of normal supply voltage.
But we didn't actually change our nominal supply voltage, the generating plant and the transmission system remained the same. The UK is still a 240Vac country that still operationally works on +-6%, but the specification allows 216Vac as our bottom limit rather than 226Vac.
Your minimum voltage for normal supply is 226Vac into your 230Vac transformer.
Your maximum voltage for normal supply is 254Vac into your 230Vac transformer. Using the regulation of the transformer, you can now determine the worst case range of secondary output voltages.
OK, so at 240Vac nominal I should get between 226Vac and 254Vac
240/230 = 1.04347826 therefore:
25Vac nominal (rated for 230Vac supply) becomes 26.08Vac in 240Vac supply
26.08 / 100 = .2608
.2608 x 94 = 94% of nominal = -6% lowest likely Vac = 24.5Vac
Right?
240/230 = 1.04347826 therefore:
25Vac nominal (rated for 230Vac supply) becomes 26.08Vac in 240Vac supply
26.08 / 100 = .2608
.2608 x 94 = 94% of nominal = -6% lowest likely Vac = 24.5Vac
Right?
you got the right answers but I don't follow the last calculation.
lowest voltage is 226/230 * 25 = 24.6Vac. Just as you said.
Highest voltage is 254/230 * 25 * transformer regulation (let's assume transformer regulation = 5%)
Highest = 254/230 * 1.05 * 25 = 29Vac
Normal voltage when mains is at 240Vac and the transformer is fully loaded is 240/230 * 25 = 26.1Vac. Again as you calculated.
Notice that the client circuit must be designed to work over that full range of possible (worst case) voltages, 24.6Vac to 29Vac.
lowest voltage is 226/230 * 25 = 24.6Vac. Just as you said.
Highest voltage is 254/230 * 25 * transformer regulation (let's assume transformer regulation = 5%)
Highest = 254/230 * 1.05 * 25 = 29Vac
Normal voltage when mains is at 240Vac and the transformer is fully loaded is 240/230 * 25 = 26.1Vac. Again as you calculated.
Notice that the client circuit must be designed to work over that full range of possible (worst case) voltages, 24.6Vac to 29Vac.
Andrew, I feel bad asking so many basic questions, but how do I go about that?
I still don't get how I do the Rset calculations either, so I've got all that yet to come...
I still don't get how I do the Rset calculations either, so I've got all that yet to come...
the two worst cases are usually:
1.) will the circuit perform as expected when lowest voltage is available.
2.) will the circuit overheat when the highest voltage is forced into the system. eg. will it cook the smoothing capacitors?
1.) will the circuit perform as expected when lowest voltage is available.
2.) will the circuit overheat when the highest voltage is forced into the system. eg. will it cook the smoothing capacitors?
Lucas, may I give an idea man? Stick the Blue raw DC thing to the mains 3-4 times a day in those likely days & hours you gonna be listening to some vinyl. Put a 220R 10W across a filter cap so some juice is being drawn. See what DC you got on the caps. If it never drops below 34V the reg will still regulate for 30V although it would be better to never drop below 35V. If its like 32VDC worse case, then stay at 28V regulated choice for Atlantic phono.
How much VDC you got now? That will drop a bit after loaded with 220R (don't touch the R -hot-) or when reg's finished.
How much VDC you got now? That will drop a bit after loaded with 220R (don't touch the R -hot-) or when reg's finished.
Thanks to you both. I have 39.5Vdc after the caps right now
The mains is coming through at 244Vac tonight.
This transformer outputs 29Vac per side
Well 29Vac x 1.41 = 41Vdc so I guess that comes out to 39.5Vdc after losses.
Seems high, but unlikely to cook 50V smoothing caps, for tonight at least. I assume these things can take the odd surge over 50Vdc???
The mains is coming through at 244Vac tonight.
This transformer outputs 29Vac per side
Well 29Vac x 1.41 = 41Vdc so I guess that comes out to 39.5Vdc after losses.
Seems high, but unlikely to cook 50V smoothing caps, for tonight at least. I assume these things can take the odd surge over 50Vdc???
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