Hi,
Milo,
The xformer on the diagram you posted states 110V 40mA.
With 0-110V + FW bridge rectifer that gives us about 150VDC, after the RC filtering it's even less but so be it.
So, with the 110V-0-110V xfromer you'll need to hook up a bridge just as in the diagram and all you that you can't do is ground the the CT.
Personally I'd work with at least twice that B+ but that would require a redesign of most Rs in the schem.
Cheers,
P.S. What I don't understand is that if the 110V is AC then the 12.6 V for the heaters must be DC or else it'll be way too high.
If the 110V is DC then the powerxformer is a 0-80 V one.
In that case a simple FW rectifier with two diodes as Choky showed would come closer to 110VDC with your xformer.
Milo,
The xformer on the diagram you posted states 110V 40mA.
With 0-110V + FW bridge rectifer that gives us about 150VDC, after the RC filtering it's even less but so be it.
So, with the 110V-0-110V xfromer you'll need to hook up a bridge just as in the diagram and all you that you can't do is ground the the CT.
Personally I'd work with at least twice that B+ but that would require a redesign of most Rs in the schem.
Cheers,
P.S. What I don't understand is that if the 110V is AC then the 12.6 V for the heaters must be DC or else it'll be way too high.
If the 110V is DC then the powerxformer is a 0-80 V one.
In that case a simple FW rectifier with two diodes as Choky showed would come closer to 110VDC with your xformer.
fdegrove said:Hi,
Milo,
The xformer on the diagram you posted states 110V 40mA.
With 0-110V + FW bridge rectifer that gives us about 150VDC, after the RC filtering it's even less but so be it.
So, with the 110V-0-110V xfromer you'll need to hook up a bridge just as in the diagram and all you that you can't do is ground the the CT.
Personally I'd work with at least twice that B+ but that would require a redesign of most Rs in the schem.
Cheers,
P.S. What I don't understand is that if the 110V is AC then the 12.6 V for the heaters must be DC or else it'll be way too high.
If the 110V is DC then the powerxformer is a 0-80 V one.
In that case a simple FW rectifier with two diodes as Choky showed would come closer to 110VDC with your xformer.
I am looking for a diagram here where that would work and I cant see one.
If you connect the bridge across the two outer points on the winding and grounding the centre tap then every half cycle
a diode in the bridge would be shorting out half the winding
The only way posible here with a bridge, is to fit it across the
centre tap and one side of the winding. which leaves a floating
winding,
you could always add a second bridge.
regrds stormy
Hi,
Stormy,
I said:
"as in the diagram and all you that you can't do is ground the the CT."
The diagram is here:
STILL NOT BIG ENOUGH...
No, you can use a bridge just the same provided you DO NOT ground the CT.
Hey, it's even an hour later for me here, ya know.
Cheers,
Stormy,
I said:
"as in the diagram and all you that you can't do is ground the the CT."
The diagram is here:
STILL NOT BIG ENOUGH...
No, you can use a bridge just the same provided you DO NOT ground the CT.
Hey, it's even an hour later for me here, ya know.
Cheers,
fdegrove said:Hi,
Stormy,
I said:
"as in the diagram and all you that you can't do is ground the the CT."
The diagram is here:
STILL NOT BIG ENOUGH...
No, you can use a bridge just the same provided you DO NOT ground the CT.
Hey, it's even an hour later for me here, ya know.
Cheers,
Verry sory mr Fdegrove,
The problem I had with can and can't is the way your english dialog came across the way you aproached the centence , a
"can" is more apropreate.
sorry for the missunderstanding.
regards stormy (insomniac) is what i should have called myself
fdegrove said:Hi,
In which case he's going to end up about ten volts short of the target voltage.
Cheers,
EDIT: Just spotted your last posting.
Don't kill yourself, will you?
No worries.
ok I can see it got to be 1 of the lesser evils here
modify the circuit with "shortfall" on half the winding, or
modify the circuit with "excesive" voltage using bridge across
full winding (or disapate a lot in heat.
if he shoves the bridge across just one side of the winding
then he has less to dissapate.
regards stormy
Ok so I did some reading up and here is where I am. The full wave rectifier setup with a centertapped transformer like choky drew would work except for the fact that the secondary winding is rated at 45ma and I would need 56ma to allow for the full wave(non brdige) circuit. So is the only other option to only use half of the winding and cut off the other half or is there an option that I have missed?
Could I do a split supply using a bridge rectifier and use half of the supply for the left channel and half of the supply for the right channel. Does it matter that the left or right channel would be using a -V relitave to the ground. It seems like that might be a problem but I have learned that my initial assumptions regarding electronics are almost always wrong.
Thanks
Milo
Could I do a split supply using a bridge rectifier and use half of the supply for the left channel and half of the supply for the right channel. Does it matter that the left or right channel would be using a -V relitave to the ground. It seems like that might be a problem but I have learned that my initial assumptions regarding electronics are almost always wrong.
Thanks
Milo
Hi,
You're welcome.
What exactly is the current rating of the xformer you have for that secondary winding alone?
The reason I ask is that whatever way you rectify, peak current may differ depending on how you rectify but you just can't pull more current steady state than the xformer can deliver.
Cheers,
You're welcome.
What exactly is the current rating of the xformer you have for that secondary winding alone?
The reason I ask is that whatever way you rectify, peak current may differ depending on how you rectify but you just can't pull more current steady state than the xformer can deliver.
Cheers,
STOP PRESS...
Hi,
O.K....I looked up the Hammond 261C6, this is a 250VAC CT xformer so in essence you should have 125-CT-125 @ 45mA + 6.3V @ 1A for a heater.
The circuit you showed draws 40mA avg, so what's the problem?
A full wave (sans bridge) will give you...where's the calc.....177 VDC max (peak) and 112.6 VDC (avg).
Ain't that grand?
Cheers,
Hi,
O.K....I looked up the Hammond 261C6, this is a 250VAC CT xformer so in essence you should have 125-CT-125 @ 45mA + 6.3V @ 1A for a heater.
The circuit you showed draws 40mA avg, so what's the problem?
A full wave (sans bridge) will give you...where's the calc.....177 VDC max (peak) and 112.6 VDC (avg).
Ain't that grand?
Cheers,
Re: STOP PRESS...
Hi,
Nice work Mr Fdegrove you da man
regards stormy
fdegrove said:Hi,
O.K....I looked up the Hammond 261C6, this is a 250VAC CT xformer so in essence you should have 125-CT-125 @ 45mA + 6.3V @ 1A for a heater.
The circuit you showed draws 40mA avg, so what's the problem?
A full wave (sans bridge) will give you...where's the calc.....177 VDC max (peak) and 112.6 VDC (avg).
Ain't that grand?
Cheers,
Hi,
Nice work Mr Fdegrove
you da manregards stormy
Fedgrove,
Ok right, thats all well and good but in my trusty Horwitz & Hill (which I need to read more i know) it says that with the setup that choky drew (sans bridge right?) that yo0u need a transformer with a current rating 1.4 times as large as with a bridge rectifier. Seeing as how the 110V winding goes through a bridge rectifier if I was to use a 110V winding on a sans bridge then wouldnt I need 56ma insted of 40ma?
Thanks
Milo
edit: I know, I know, Im sure that Im missing something else.
Ok right, thats all well and good but in my trusty Horwitz & Hill (which I need to read more i know) it says that with the setup that choky drew (sans bridge right?) that yo0u need a transformer with a current rating 1.4 times as large as with a bridge rectifier. Seeing as how the 110V winding goes through a bridge rectifier if I was to use a 110V winding on a sans bridge then wouldnt I need 56ma insted of 40ma?
Thanks
Milo
edit: I know, I know, Im sure that Im missing something else.
Hi,
Remember when I brought up effeciency?
What Horowitz & Hill mean is peak current and voltage. By which I assume they compared it to a half wave rectifier.
Since the output waveform is essentially a sine wave with both alternations at the same polarity, the average current or voltage is 63.7 percent (or 0.637) of the peak current or voltage.
So, when we do the equations we'll see that this type of rectifier isn't very effecient, in fact compared to a FW bridge we lose about half the voltage.
But, and this is what you're missing, we have 125-CT-125, so it almost amounts to doing the same math with a 0-125 volt xformer and using the formula for a FW bridge:
125 * 1.141 = 142.625.
The math I did on your xformer arrived at about 112 volt for the FW using the entire xformer.
As you can see it's not that far apart but the FW is dreadfully inefficient at just 63.7% which is why a FW bridge is almost universally used in modern electronics: 114% efficiency.
So the FW bridge produces the same peak voltage as the half wave rectifier but with the same frequency of the FW rectifier.
Neither of the equations included the voltage drop of the diodes ( 0.6 V per diode usually) as it is neglible for all practical purposes.
Hope this helps,
Remember when I brought up effeciency?
What Horowitz & Hill mean is peak current and voltage. By which I assume they compared it to a half wave rectifier.
Since the output waveform is essentially a sine wave with both alternations at the same polarity, the average current or voltage is 63.7 percent (or 0.637) of the peak current or voltage.
So, when we do the equations we'll see that this type of rectifier isn't very effecient, in fact compared to a FW bridge we lose about half the voltage.
But, and this is what you're missing, we have 125-CT-125, so it almost amounts to doing the same math with a 0-125 volt xformer and using the formula for a FW bridge:
125 * 1.141 = 142.625.
The math I did on your xformer arrived at about 112 volt for the FW using the entire xformer.
As you can see it's not that far apart but the FW is dreadfully inefficient at just 63.7% which is why a FW bridge is almost universally used in modern electronics: 114% efficiency.
So the FW bridge produces the same peak voltage as the half wave rectifier but with the same frequency of the FW rectifier.
Neither of the equations included the voltage drop of the diodes ( 0.6 V per diode usually) as it is neglible for all practical purposes.
Hope this helps,
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