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Old 10th July 2003, 05:56 PM   #11
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man this "you are under moderation" stuff is really annoying....

anyway i think i found my problem. i have a spst switch and i wired the "neutral" on to the switch instead of "hot". now i have 0.00v dc when the power plug is in and switch is off and +-22.9v dc when switch is on.

My remaining concern is that somehow I am not getting the 25/0.707 ~ +-35 v dc output as I should be getting. Does this have anything to do with the way I wired up the 2 bridges?
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Old 10th July 2003, 10:21 PM   #12
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Quote:
Originally posted by rocktboy
man this "you are under moderation" stuff is really annoying....

anyway i think i found my problem. i have a spst switch and i wired the "neutral" on to the switch instead of "hot". now i have 0.00v dc when the power plug is in and switch is off and +-22.9v dc when switch is on.

My remaining concern is that somehow I am not getting the 25/0.707 ~ +-35 v dc output as I should be getting. Does this have anything to do with the way I wired up the 2 bridges?
"...switch is off and +-22.9v dc when switch..." You mean +-22.9v AC, not DC. I'm assuming that's the transformer output measured where they connect to the bridge. If thats the case you should be getting about 33VDC on the output of the bridge minus 1 or 2 volt you'll drop across the bridge.
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Old 10th July 2003, 11:04 PM   #13
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Originally posted by roddyama

"...switch is off and +-22.9v dc when switch..." You mean +-22.9v AC, not DC. I'm assuming that's the transformer output measured where they connect to the bridge. If thats the case you should be getting about 33VDC on the output of the bridge minus 1 or 2 volt you'll drop across the bridge.
yes you heard me correct. i have 25v, 25v AC going to the bridge and +-22.9v DC out from the bridge.



it measures that on both bridges so the bridge themselves shouldn't be the problem.....
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Old 11th July 2003, 12:06 AM   #14
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On the output of the bridge, with out filter caps, you have full wave rectified AC. This will take the form of 120Hz half sinewave bumps with peaks of about 33V. If you measure this with a dc meter you should measure 33V X .707 ~ 23VDC.

Connect a PSU cap to the output of the bridge and let it charge and you should have your ~33VDC. During your test, you might want to connect a resistor across the cap so it will discharge. Maybe 1W 200ohm. It would be best if you had a variac to slowly raise to voltage.
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Old 11th July 2003, 05:15 AM   #15
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Originally posted by roddyama
During your test, you might want to connect a resistor across the cap so it will discharge. Maybe 1W 200ohm. It would be best if you had a variac to slowly raise to voltage.
Sorry, that's going to have to be at least a 5W resistor, and 10W would be better, or go to 250ohms@5W.
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Old 11th July 2003, 07:43 AM   #16
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yes you heard me correct. i have 25v, 25v AC going to the bridge and +-22.9v DC out from the bridge.
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If you measure this with a dc meter you should measure 33V X .707 ~ 23VDC.
Am I missing something here? What's the problem? He should be getting ~23DC and he IS getting 22.9! I don't think that he need worry about 0.1DC.
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Old 11th July 2003, 08:49 AM   #17
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Originally posted by rocktboy

I have a single 25v 0v 25v secondary so I hooked the two 25v wires to the two ac in's on the first bridge. I simply did the same thing to the second bridge (so in effect the 2 bridges are in parallel?) so I have 2 channels of +-V dc. And the 0v wire goes to the power star ground. Anything wrong with what I am doing?
If you have a centre-tapped transformer (25-0-25), use only one bridge.


Quote:
Originally posted by rocktboy
anyway i think i found my problem. i have a spst switch and i wired the "neutral" on to the switch instead of "hot". now i have 0.00v dc when the power plug is in and switch is off and +-22.9v dc when switch is on.
That's why I use double switches, as I told on a previous note.
That way you disconnect the two wires, and you don't have to be worried about incorrect wiring on your electrical system.
In continental Europe it's worst still, as you can connect the mains plug to the plug on the wall in any position.
UK plugs are better, as they have a central ground pin and you can't reverse them.
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Old 11th July 2003, 09:57 AM   #18
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Originally posted by Nuuk
Am I missing something here? What's the problem? He should be getting ~23DC and he IS getting 22.9! I don't think that he need worry about 0.1DC.
I think he's confused because he's expecting to get 25V times 1.414 (35V), but of course he won't get that until he's connected the resevoir capacitors.

How are you getting on with your buffer problem?

Cheers,

Mark
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Old 11th July 2003, 05:55 PM   #19
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Originally posted by mhennessy


I think he's confused because he's expecting to get 25V times 1.414 (35V), but of course he won't get that until he's connected the resevoir capacitors.

How are you getting on with your buffer problem?

Cheers,

Mark

what Mark said.....

the danger with gaincloning is that newbies like me who has absolutely zero knowledge in electronics will try to build one because it's simple and cheap enough.

i'll get it up and running this afternoon. thank you all for patiently answering my type of questions......
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Old 11th July 2003, 08:24 PM   #20
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the danger with gaincloning is that newbies like me who has absolutely zero knowledge in electronics will try to build one because it's simple and cheap enough.
That's one reason that I did the 'Gainclone beginner's page
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