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Centre tap split rail supply from twin secondaries
Centre tap split rail supply from twin secondaries
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Old 7th March 2018, 12:38 PM   #1
Puffin is offline Puffin  United Kingdom
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Default Centre tap split rail supply from twin secondaries

I think I am going mad! I have made many CT supplies using a twin sec transformer but I cannot seem to get this one to work.

I have a dual 55vac tranny and have joined the centre pair. when connected to the bridge I am only getting 112v between + & - and + & CT 56vdc and - & CT 56vdc. I was expecting around 75vdc per rail. What have I done wrong?
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Old 7th March 2018, 01:09 PM   #2
audiofan is offline audiofan  Canada
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You should show a schematic diagram of your circuit ....

Are you using filter capacitor ... ??
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Old 7th March 2018, 01:10 PM   #3
Puffin is offline Puffin  United Kingdom
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I think I might have answered my own question? Should I be using 2 bridge rectifiers as in this circuit I used for Gainclones?
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Old 7th March 2018, 03:48 PM   #4
DF96 is offline DF96  England
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If you have two identical secondaries you can use them to make a bipolar DC supply in two ways:
1. Join them to make a CT secondary and use one bridge.
2. Leave them separate, use two bridges and join the DC outputs.
Any attempt to mix these two methods is likely to result in problems.
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Old 7th March 2018, 06:47 PM   #5
Puffin is offline Puffin  United Kingdom
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Quote:
Originally Posted by DF96 View Post
If you have two identical secondaries you can use them to make a bipolar DC supply in two ways:
1. Join them to make a CT secondary and use one bridge.
2. Leave them separate, use two bridges and join the DC outputs.
Any attempt to mix these two methods is likely to result in problems.
I did 1. as above, but connecting the outer secondaries to the bridge (the inner pair joined to make the CT) did not result in the 1.4 dc multiplier that I would have expected. I therefore assumed that I had done something wrong. The last time I built a Gainclone PS was about 10 years ago and I think I have gone silly

Last edited by Puffin; 7th March 2018 at 06:50 PM.
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Old 7th March 2018, 07:01 PM   #6
scottjoplin is offline scottjoplin  Wales
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You were asked if you are using filter capacitors, I hope so.
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Old 7th March 2018, 07:10 PM   #7
Puffin is offline Puffin  United Kingdom
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Yes, sorry I missed that one. As the filter caps follow the bridge rectifier I have so far only connected the tranny to the bridge and expected to see an increase in the dc volts.
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Old 7th March 2018, 07:17 PM   #8
scottjoplin is offline scottjoplin  Wales
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No, you won't see that until the rectified pulses are smoothed
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Old 7th March 2018, 07:24 PM   #9
Puffin is offline Puffin  United Kingdom
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Oh dear, I have obviously lost what I knew in the past. Thanks.
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Old 8th March 2018, 12:20 AM   #10
nezbleu is offline nezbleu  Canada
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Centre tap split rail supply from twin secondaries
Also, don't show us a schematic that you aren't using, there are an infinite number of those. Show us the schematic of the circuit you are actually measuring.
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