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Old 19th November 2009, 11:13 AM   #51
teleman is offline teleman  Norway
diyAudio Member
Join Date: Jul 2008
Per Anders,
I think I know where/what the problem might be!!! I've not GROUNDED the center tap at all...left it just floating!!!I think I'll change my name to STUPID! any better suggestions? he..he.. Thanks.
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Old 19th November 2009, 02:43 PM   #52
teleman is offline teleman  Norway
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Join Date: Jul 2008
Would this be the correct way to ground the PSU?
1.Main Filter/socket ground NOT GROUNDED'... ie:no connection?
2.PSU '0'v grounded to PSU chassis?
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Old 20th November 2009, 05:26 PM   #53
teleman is offline teleman  Norway
diyAudio Member
Join Date: Jul 2008
I found out that I had inadvertently soldered the - leg of the 2200uF cap on the + rail between reg.adj/res/trim.This was the cause of the instability! After correcting it,both rails are now working as they should & the strange step like spike display on the scope too is gone now!.

Then I extended the connection from the common-'0'- rail as shown in the circuit dia, to the psu chassis...& then suddenly both LEDs went off.A closer inspection showed that although both the fuses were intact,yet they were completely burnt out!

I,then disconnected the "ground", fitted new they're working again.
Q:Has anyone any clue/explanation as to why this may have happened?

Reading from several articles,I find that some emphasize on the importance of this while others don't! It's all a bit confusing.

I think I was lucky,that I had 2 fuses on the secondaries,will,strongly recommend adding fuses to this circuit to anyone wishing build this psu! 'Though i accidentally shorted the rails a few times,the diodes & the fuses saved my day I am sure!
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Old 20th November 2009, 09:34 PM   #54
teleman is offline teleman  Norway
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Join Date: Jul 2008
Found this article on "Circuit Grounds & Grounding Practices by George Hunka which I'm sure would be of interest to novices like me.The web site would not upload!
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Old 8th January 2010, 11:19 PM   #55
teleman is offline teleman  Norway
diyAudio Member
Join Date: Jul 2008
I thought I'd write a few notes on this PSU project since it was completed a few weeks ago & is now in regular use on my bench!

The most important thing are the two trimming pots! I managed to burn 2 of these since I wasn't careful enough when adjusting the voltages.In my haste to finish it quickly,I had inadvertently turned them far to quickly I suppose,which resulted in these burning out!
So turn them VERY VERY slow folks!
The tell tale signs are that no matter how much you adjust the trimpots,the voltages would fluctuate regardless & will show different levels on power up every time!

Secondly,incorporating fuses on the secondary side of the trafo actually prevented major disasters I think. I blew about 25 fuses mostly by accidentally shorting test probes,bad soldering on various projects, damage was done either to my circuits or to the psu itself!

Adding LED's,as voltage indicators help the PSU from voltage drift on no load conditions I think.(Perhaps some expert out there would know why I'm sure)

It's VERY quiet & I cannot hear any additional noise at all (This could also be possible/plausible that man is going deaf!)

Thanks for everyone who have helped & guided me through this.Much appreciated.

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