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Old 23rd May 2013, 07:02 PM   #21
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Ok, but i dont get what the next step is. I meassured some things, but what exactly am i going to find out. If i wanna use it for a gainclone, shouldnt i establish the best connection in terms of the input for the gainclone and not what was intended for this old amp (I think it was a 20W amp)??
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Old 23rd May 2013, 07:04 PM   #22
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I've tried to establish the primaries and the secondaries. The rest is up to a bit of experimentation.

Now you know which are the secondaries you need to load them up and see what sort of currents they can provide.

Last edited by KatieandDad; 23rd May 2013 at 07:07 PM.
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Old 23rd May 2013, 07:12 PM   #23
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"Establish" in wich way? Am i right that my next step is to find the best connection of the primary wires to get the correct output voltage. I think the gainclone system i want to build, needs a 18VAC output. That would give the transformer a 12.7 ratio. This ratio is my goal right?
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Old 24th May 2013, 08:45 AM   #24
AndrewT is offline AndrewT  Scotland
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use a mains bulb tester
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Old 24th May 2013, 09:16 AM   #25
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Quote:
Originally Posted by TroelsG View Post
"Establish" in wich way? Am i right that my next step is to find the best connection of the primary wires to get the correct output voltage. I think the gainclone system i want to build, needs a 18VAC output. That would give the transformer a 12.7 ratio. This ratio is my goal right?
NO. Try doing a bit of research of how a transformer works. Generally you cannot play around with the primary tappings to get the correct output voltage. A 110V primary is designed to run at 110V, yes you could use less primary voltage but this is not what we are aiming to acieve here.

You have two primaries, the second of which has a few extra turns to enable it to run with a slightly higher voltage.

AndrewX is harping on about a bulb tester, you don't need one just yet, we are still trying to establish the phasing of the primaries.
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Old 24th May 2013, 10:25 AM   #26
AndrewT is offline AndrewT  Scotland
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The bulb tester allows you to safely power up mis-wired primaries.
it is in my view an indispenable tool.

A dual primary or multitapped primary is potentially the most dangerous bit of kit us experimenters can get a hold of.
The bulb tester solves the danger bit.
It even prevents the blown fuse.
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Old 24th May 2013, 10:46 AM   #27
DF96 is offline DF96  England
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He will need a bulb tester when he first connects it to mains, so best to buy the parts for that now so he is not tempted to try without it when the time comes. Nowadays I would use this even for a brand new transformer from a reliable supplier. So simple, so cheap, and so useful. Also a good test of wiring ability: someone who can't build a safe bulb tester, or requires detailed instructions for it, should not be building mains PSUs.
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Old 24th May 2013, 11:10 AM   #28
AJT is offline AJT  Philippines
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Quote:
Originally Posted by TroelsG View Post
"Establish" in wich way? Am i right that my next step is to find the best connection of the primary wires to get the correct output voltage. I think the gainclone system i want to build, needs a 18VAC output. That would give the transformer a 12.7 ratio. This ratio is my goal right?
if you have another small traffo with say 6 volts secondary, things will be easier...
i never used the bulb tester, never needed one, but that is just me...
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Old 24th May 2013, 04:21 PM   #29
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I think i found the right connections: (I used a 11 volt transformer and meassured output on the Blue-Black)

I tried the following settings.

240: Black-Blue connected/Current on Yellow-Red: Ratio: 13.222

220: Black-Blue connected/Current on Brown-Red: Ratio: 11.55

110: Current on Blue-Red. Ratio: 5.89

130: Current on Black-Yellow. Ratio: 6.91

Could this be the connections for the four inputs. I think it makes sense. It would create an output at:

110: 18.67V
130: 18.81V
220: 18.86V
240: 18.15V

Thanks again

Last edited by TroelsG; 24th May 2013 at 04:41 PM.
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Old 24th May 2013, 09:06 PM   #30
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Quote:
Originally Posted by TroelsG View Post
I think i found the right connections: (I used a 11 volt transformer and meassured output on the Blue-Black)

I tried the following settings.

240: Black-Blue connected/Current on Yellow-Red: Ratio: 13.222

220: Black-Blue connected/Current on Brown-Red: Ratio: 11.55

110: Current on Blue-Red. Ratio: 5.89

130: Current on Black-Yellow. Ratio: 6.91

Could this be the connections for the four inputs. I think it makes sense. It would create an output at:

110: 18.67V
130: 18.81V
220: 18.86V
240: 18.15V

Thanks again
And also what VA value do you think it is, anyway i can find out? Big enough to handle a gainclone? It weighs 1726 grams.
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