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P/Supply board _ Which resistor to change?
P/Supply board _ Which resistor to change?
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Old 19th July 2019, 10:04 PM   #1
gigigirl is offline gigigirl
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Default P/Supply board _ Which resistor to change?

Hi Guys, A little help please. I stupidly ordered two of these boards without fully reading the description, Thinking they were adjustable, I need 18 VDC but got the default 5 VDC.

LT1963A LT1963 regulated power supply board for decoding, preamplifier coaxial | eBay

The vendor advises I just need to change the resistors, But can anyone advise what value? Or do I just need to increase or decrease the resistance by trial & error to get it right.

Cheers
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Old 19th July 2019, 10:08 PM   #2
gigigirl is offline gigigirl
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Default Picture of un-populated board

Picture of un-populated board
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Old 19th July 2019, 10:23 PM   #3
rayma is offline rayma  United States
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It's difficult to tell the resistor values on the board, but use

18V = 1.21V x ( 1 + R2/R1 ) .... and then 13.88 x R1 = R2

Keep R2 the same, and decrease R1.
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Old 20th July 2019, 01:45 AM   #4
gigigirl is offline gigigirl
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Hi, Thanks rayma I will give that a go.

Cheers
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Old 16th September 2019, 05:24 AM   #5
gigigirl is offline gigigirl
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Well finally got around to change the resistors.
Unit works OK, but is not what I would call now noise. Definitely not suitable for phono or dac. Cheers
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Old 16th September 2019, 08:38 AM   #6
johnego is offline johnego  Indonesia
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Yes, it is not low noise (see picture) but surprisingly it (something based on this chip) was in the fourth place in blind listening comparison just below Jung/Didden, Burson and Sjostrom.
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Old 16th September 2019, 08:52 AM   #7
Mooly is offline Mooly  United Kingdom
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P/Supply board _ Which resistor to change?
Quote:
Originally Posted by gigigirl View Post
Well finally got around to change the resistors.
Unit works OK, but is not what I would call now noise. Definitely not suitable for phono or dac. Cheers
Have you proved your phono stage to be silent when using a different supply as it is possible the noise is not related to the supply? Have you looked at the regulator outputs on a scope?
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Old 16th September 2019, 09:06 AM   #8
Ketje is offline Ketje  Belgium
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Not advisable to use the LT1963 for 18V out. The max input is 20V leaving not much space for a ripple on the rectified DC.
Mona
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Old 16th September 2019, 08:38 PM   #9
gigigirl is offline gigigirl
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Hi Guy's, Yes my AD797 Phono Amp is very, very quiet when using SLA batteries.
I was originally planning to use one of these at 18 V, but then they came in a pair to allow +/- operation. So initial test was done at 12 V.

Cheers
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