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snimater1
 Post subject: 2A3 SE PROBLEMS
PostPosted: Wed May 05, 2010 12:26 am 
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DEAR CHUNG I JUST FINISHED THE PROJECT WITH THE 6SN7,2X ECC88 AND 2A3 BASED ON YOUR SCHEMATIC.PLEASE COULD YOU TELL ME THE PROPER VOLTAGES ON EVERY STAGE? I AM ASKING YOU BECAUSE ITS NOT WORKING WELL. I HEAR SOME NUSTY NOISES. I HAVE TO TELL YOU THAT I AM USING THESE TUBES: 6HC8, 2X 12AU7 AND SHUNGUANG 2A3'S. THANKS FOR YOUR TIME.
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Ivan Li
 Post subject: Re: 2A3 SE PROBLEMS
PostPosted: Wed May 05, 2010 9:44 am 
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snimater1 wrote:
DEAR CHUNG I JUST FINISHED THE PROJECT WITH THE 6SN7,2X ECC88 AND 2A3 BASED ON YOUR SCHEMATIC.PLEASE COULD YOU TELL ME THE PROPER VOLTAGES ON EVERY STAGE? I AM ASKING YOU BECAUSE ITS NOT WORKING WELL. I HEAR SOME NUSTY NOISES. I HAVE TO TELL YOU THAT I AM USING THESE TUBES: 6HC8, 2X 12AU7 AND SHUNGUANG 2A3'S. THANKS FOR YOUR TIME.


Is it 6H8C?

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Ivan Li

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snimater1
 Post subject: Re: 2A3 SE PROBLEMS
PostPosted: Wed May 05, 2010 5:28 pm 
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YES IT IS. SORRY FOR MY MISTAKE. THE SOUND IS DISTORTED AND THERE IS A NUSTY NOISE BUT NOT HUM. IT IS LIKE YOU ARE HITTING SOMETHING GUP... GUP...GUP. SOMETHING LIKE THAT. I SUSPECT THAT THERE IS AN OVERDRIVE BETWEEN THE STAGES.THANKS.
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chung
 Post subject: Re: 2A3 SE PROBLEMS
PostPosted: Thu May 06, 2010 3:51 pm 
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Hello snimater1,

Since it was an old project for a friend. Would you measure the DC voltage on cathode/grid/plate of each tube to find out the problem?

Regards

Chung
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snimater1
 Post subject: Re: 2A3 SE PROBLEMS
PostPosted: Thu May 06, 2010 6:59 pm 
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dear chung at last i found the problem. i tried to make a modification in the schematic by putting potensiometer in the cathode of the 2a3's. I got it away and the problem solved. Now my only problem is the hum. Can i put bigger caps in the psu?
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chung
 Post subject: Re: 2A3 SE PROBLEMS
PostPosted: Mon May 10, 2010 2:56 pm 
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Sure, you can add some more capacitor to test any improvement.

Chung
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amp_mangler
 Post subject: Re: 2A3 SE PROBLEMS
PostPosted: Tue May 11, 2010 7:09 am 
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Hi snimater1,

can we have picture of the amp please ?
underneath and on top :)

regards
Joe
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snimater1
 Post subject: Re: 2A3 SE PROBLEMS
PostPosted: Wed May 12, 2010 1:46 am 
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hi everybody and thanks for your replies. i added an 100μF cap in the psu and the hum gone completely. i will post some photos of my amp real soon.thanks jorge.
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chung
 Post subject: Re: 2A3 SE PROBLEMS
PostPosted: Wed May 12, 2010 5:23 pm 
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Excellent!! A simple 100uF solve the problem!!
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