Mains TX connections Help

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colin.hepburn
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#1 Mains TX connections Help

Post by colin.hepburn »

Hi All
Just wanted to check Mains TX connections
TX mounted on aluminum panel
if using a 150-0-150v CT@100mA with a SS Bridge Rec to get 0-300v is the CT left unconnected or should it go to main earth also does the 100mA current change any
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#2

Post by pre65 »

If using a CT transformer with windings in series, with a bridge, the CT is left unconnected.

What make and model is your transformer ? You might not be using it within its limits if you want 100ma from both windings at once, CT transformers are rated to work one half at a time.
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#3

Post by colin.hepburn »

It's me little Danbury 150-.0-150v@100mA I want to rebuilt my 5751/12B4a headphone amp with a bit more current upping it from 30mA to about 50mA
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#4

Post by pre65 »

colin.hepburn wrote:It's me little Danbury 150-.0-150v@100mA I want to rebuilt my 5751/12B4a headphone amp with a bit more current upping it from 30mA to about 50mA
Mike will chip in about that before too long. I was thinking about some of the Hammond transformers. :)
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#5

Post by colin.hepburn »

pre65 wrote:
colin.hepburn wrote:It's me little Danbury 150-.0-150v@100mA I want to rebuilt my 5751/12B4a headphone amp with a bit more current upping it from 30mA to about 50mA
Mike will chip in about that before too long. I was thinking about some of the Hammond transformers. :)
Well yes it is a beef up Hammond 369BX I had made up by Denbury john
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#6

Post by pre65 »

colin.hepburn wrote:
pre65 wrote:
colin.hepburn wrote:It's me little Danbury 150-.0-150v@100mA I want to rebuilt my 5751/12B4a headphone amp with a bit more current upping it from 30mA to about 50mA
Mike will chip in about that before too long. I was thinking about some of the Hammond transformers. :)
Well yes it is a beef up Hammond 369BX I had made up by Denbury john
I did wonder cos I could not see such a transformer on Mikes web site. I thought the bloke at Danbury was Dave. :?
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#7

Post by colin.hepburn »

pre65 wrote:
colin.hepburn wrote:
pre65 wrote:
Mike will chip in about that before too long. I was thinking about some of the Hammond transformers. :)
Well yes it is a beef up Hammond 369BX I had made up by Denbury john
. I thought the bloke at Danbury was Dave. :?
it is did i say john :)
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#8

Post by Mike H »

pre65 wrote:I did wonder cos I could not see such a transformer on Mikes web site. I thought the bloke at Danbury was Dave. :?
He is. :D
 
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#9

Post by Mike H »

I think this was a special was it? Memory is hazy ... no change there then ......

Probably say 75mA max. to be on the safe side, as 300VAC. So 50mA should be fine.

HTH

PS: Phil's right there's a difference in terms of how much heat it will tolerate, double CT versus single winding. I think. Perversely, because a CT winding is double the turns it could make it bigger than a single winding version anyway :D
 
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#10

Post by colin.hepburn »

Hi mike
Yes it was the swap on the Marshall Mains OPTX i had
Cant remember if its 50/100VA but its 300vCT @100mA uprated Hammond 369 is the ct left unconnected then heres the psu but at about 50ma load not the 67mA sa on the this schematic
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#11

Post by pre65 »

On that diagram the centre tap is at 0v because it uses a valve full wave rectifier. Not sure why it's got 2 extra diodes though.

Thinking about it, it is a hybrid bridge, so perhaps the centre tap is NOT grounded, just left as 0v.

Thinking again, it's got a rectifier valve within a diode bridge, with a switch to change from one t'other, never seen that before. :?
Last edited by pre65 on Sat Jan 05, 2013 11:18 pm, edited 1 time in total.
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colin.hepburn
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#12

Post by colin.hepburn »

pre65 wrote:On that diagram the centre tap is at 0v because it uses a valve full wave rectifier. Not sure why it's got 2 extra diodes though.

Thinking about it, it is a hybrid bridge, so perhaps the centre tap is NOT grounded, just left as 0v.
That psu is custom so you can switch to use valve or ss I will just using the the SS Bridge rec only
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#13

Post by Mike H »

Yes it's switchable valve o/p or SS o/p, the 2 extra diodes are for the SS o/p
 
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#14

Post by colin.hepburn »

Yep I will be using the SS diode way what I and trying to get at is the 0v the CT tap left unconnected
and is the TX current still 100mA or raised to 200mA if the 0V CT is not used giving me about 0-300v
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#15

Post by colin.hepburn »

Ok looking at that psu I posted earlier using a CT with a switchable valve / Bridge rectifier arrangement don't seem right for a single rail supple as all psu schematic I have come across that are using a CT with SS Bridge rectifiers are all split rail +/_ :?
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