GC Split Rail Supply

Puffin · 30th January 2012, 09:30 AM

I have re-built a power supply to power some bridged GCs that I built, tested and never used. Basically it is to tidy things up so that I could safely use the amps.

The Trannys are 300va 25 + 25 AC. I was using Carlos Filipe's schematic for the original rectifiers and seem to remember that each rail was around 42 - 45vdc (just within the 3886 limit)

To tidy things up I have used some generic rectifier boards. The resistors are 2.2k between rails and 1R elsewhere. There are 2 R1's on each rail (one under the board on each side)

I am getting roughly 51vdc after rectification which is too high. I asssume that I could reduce this by changing the resistor values. Am I correct?

madtecchy · 30th January 2012, 09:41 AM

Hi Puffin i cant understand how you get 51v dc from a transformer with 25 volt ac secondrys.. it is not a good idea to reduce the voltage by changing the resistor.

Regards Ian

Puffin · 30th January 2012, 09:50 AM

No, neither can I!

Puffin · 30th January 2012, 10:13 AM

The only other thing I did was to add a wima from rail to rail (under the board). I have done this before with no problems.

pinkmouse · 30th January 2012, 10:23 AM

Something is very wrong. With 25-0-25 traffos, I would be expecting to see about 35V out of that PSU. Not 42-45V, and definitely not 51V. How are you measuring?

wintermute · 30th January 2012, 10:37 AM

Puffin have you measured the AC voltage coming out of the traffo? Are you sure it isn't a 35 - 0 -35 transformer?

Tony.

Puffin · 30th January 2012, 11:03 AM

These are the trannys I am using :-

CLAIRTRONIC|12082|TRANSFORMER, 300VA 2X 25V | Farnell United Kingdom

I have measured both and the secondarys are 38vac! I am not sure what is going on. It is so long since I used them that I assume they must have measured correctly on receipt.

madtecchy · 30th January 2012, 11:14 AM

Im also thinking you have a 35-0-35 trafo. Do you have the primarys wired corectly

Puffin · 30th January 2012, 11:30 AM

Quote:

Originally Posted by madtecchy

Im also thinking you have a 35-0-35 trafo. Do you have the primarys wired corectly

Primaries are fine.

AndrewT · 30th January 2012, 11:40 AM

Dual primaries should show ~240Vac across the series pair.
Then show ~120Vac across each single primary.

Check that.

Is your bulb lighting up?

30th January 2012, 09:30 AM	#1
Puffin diyAudio Member Join Date: Feb 2006 Location: U.K	GC Split Rail Supply I have re-built a power supply to power some bridged GCs that I built, tested and never used. Basically it is to tidy things up so that I could safely use the amps. The Trannys are 300va 25 + 25 AC. I was using Carlos Filipe's schematic for the original rectifiers and seem to remember that each rail was around 42 - 45vdc (just within the 3886 limit) To tidy things up I have used some generic rectifier boards. The resistors are 2.2k between rails and 1R elsewhere. There are 2 R1's on each rail (one under the board on each side) I am getting roughly 51vdc after rectification which is too high. I asssume that I could reduce this by changing the resistor values. Am I correct?

30th January 2012, 10:23 AM	#5
pinkmouse diyAudio Moderator Join Date: Apr 2002 Location: Chatham, England	Something is very wrong. With 25-0-25 traffos, I would be expecting to see about 35V out of that PSU. Not 42-45V, and definitely not 51V. How are you measuring? __________________ Al I conceive of nothing, in religion, science or philosophy, that is more than the proper thing to wear, for a while. Charles Fort

30th January 2012, 10:37 AM	#6
wintermute just another diyAudio Moderator Join Date: Aug 2003 Location: Sydney Blog Entries: 22	Puffin have you measured the AC voltage coming out of the traffo? Are you sure it isn't a 35 - 0 -35 transformer? Tony. __________________ Any intelligence I may appear to have is purely artificial! Some of my photos

30th January 2012, 11:40 AM	#10
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Dual primaries should show ~240Vac across the series pair. Then show ~120Vac across each single primary. Check that. Is your bulb lighting up? __________________ regards Andrew T.

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30th January 2012, 09:41 AM	#2
madtecchy diyAudio Member Join Date: Dec 2010 Location: wigan	Hi Puffin i cant understand how you get 51v dc from a transformer with 25 volt ac secondrys.. it is not a good idea to reduce the voltage by changing the resistor. Regards Ian

30th January 2012, 09:50 AM	#3
Puffin diyAudio Member Join Date: Feb 2006 Location: U.K	No, neither can I!

30th January 2012, 10:13 AM	#4
Puffin diyAudio Member Join Date: Feb 2006 Location: U.K	The only other thing I did was to add a wima from rail to rail (under the board). I have done this before with no problems.

30th January 2012, 11:03 AM	#7
Puffin diyAudio Member Join Date: Feb 2006 Location: U.K	These are the trannys I am using :- CLAIRTRONIC\|12082\|TRANSFORMER, 300VA 2X 25V \| Farnell United Kingdom I have measured both and the secondarys are 38vac! I am not sure what is going on. It is so long since I used them that I assume they must have measured correctly on receipt.

30th January 2012, 11:14 AM	#8
madtecchy diyAudio Member Join Date: Dec 2010 Location: wigan	Im also thinking you have a 35-0-35 trafo. Do you have the primarys wired corectly

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