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Old 23rd March 2004, 09:08 PM   #21
stormy is offline stormy  United Kingdom
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Quote:
Originally posted by A3rd.Zero
I dont know if the powersupply section calls for delivery of 110V or if that is just the winding of the transformer that they used (the schematic is a little unclear because they never give voltages at test points). If I were to construct a powersupply as below, wouldnt I have basically 110V (not taking into account RMS due to the rectifier or the caps) and just twice the amperage that each side of the winding could produce? Again sorry if I'm totally missing something.

Thanks,

Milo

Come on guys how can you connect a transformer winding like that!.
you can only wire seperate windings in paralel if you connect a winding with a centre tap like that you have effectivly shorted
out the winding Come on look @ it.


Regards stormy
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Old 23rd March 2004, 11:11 PM   #22
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Ok, right I see that, sorry.

thanks,

milo
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Old 23rd March 2004, 11:36 PM   #23
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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.
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Old 24th March 2004, 12:25 AM   #24
stormy is offline stormy  United Kingdom
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Quote:
Originally posted by fdegrove
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
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Old 24th March 2004, 12:33 AM   #25
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Hi,

Stormy,

Quote:
If you connect the bridge across the two outer points on the winding and grounding the centre tap then every half cycle
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...

Quote:
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,
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,
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Old 24th March 2004, 12:40 AM   #26
stormy is offline stormy  United Kingdom
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Just had a thought for your spare winding.
you could fit a smaller stepdown transformer on that winding and supply your heater.

hehe

i think shiftys 2 diode and center tap ground is going to be
your best bet.



regards stormy.
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Old 24th March 2004, 12:46 AM   #27
stormy is offline stormy  United Kingdom
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Quote:
Originally posted by fdegrove
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
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Old 24th March 2004, 12:49 AM   #28
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Hi,

Quote:
i think shiftys 2 diode and center tap ground is going to be
In which case he's going to end up about ten volts short of the target voltage.

Cheers,

EDIT: Just spotted your last posting.

Quote:
regards stormy (insomniac) is what i should have called myself
Don't kill yourself, will you?

No worries.
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Old 24th March 2004, 01:00 AM   #29
stormy is offline stormy  United Kingdom
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Quote:
Originally posted by fdegrove
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
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Old 24th March 2004, 01:05 AM   #30
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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
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