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Old 19th October 2007, 01:14 AM   #1931
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I use Chris VH's Flavor 2 cords. Its an excellent cord and fairly priced as well.

Yes, power cords make differences on gainclones.

Best,
Anand.
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Old 19th October 2007, 07:05 PM   #1932
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the dac kit is still available ?
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Old 22nd October 2007, 03:19 AM   #1933
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Default USB DAC

Hi Peter,

I'm just getting around to building my USB DACs, and hit a small problem. When I powered up the first one, C3 heated up to the point that it started swelling, and of course the DAC was not working.

I've checked all the component values, polarities (especially C1 and C3) , and pin orientations, and cannot find anything wrong.

I've removed C3, and in addition to being visibly swollen, it does not measure consistently in value.

I have 10Vac out from both legs of the transformer, and the following voltages at the input to the DAC:

R1-R2: 12.5Vdc in, 10.2Vdc out.
R3-R4: 9.2Vdc in, 6.2Vdc out (with C3 removed).

I doubt that C3 was defective before....any suggestions of where to look further before replacing C3?
Thanks,
Robert
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Old 22nd October 2007, 03:35 AM   #1934
jleaman is offline jleaman  Belgium
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No magic Smoke ?
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Old 22nd October 2007, 04:00 AM   #1935
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Quote:
Originally posted by jleaman
No magic Smoke ?
No smoke....
But C3 definitely heated up!
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Old 22nd October 2007, 04:22 AM   #1936
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Default Re: USB DAC

Quote:
Originally posted by rjkdivin
Hi Peter,

I'm just getting around to building my USB DACs, and hit a small problem. When I powered up the first one, C3 heated up to the point that it started swelling, and of course the DAC was not working.

I've checked all the component values, polarities (especially C1 and C3) , and pin orientations, and cannot find anything wrong.

I've removed C3, and in addition to being visibly swollen, it does not measure consistently in value.

I have 10Vac out from both legs of the transformer, and the following voltages at the input to the DAC:

R1-R2: 12.5Vdc in, 10.2Vdc out.
R3-R4: 9.2Vdc in, 6.2Vdc out (with C3 removed).

I doubt that C3 was defective before....any suggestions of where to look further before replacing C3?
Thanks,
Robert
Here a couple of photos just in case anyone can spot anything out of place:

Click the image to open in full size.
Click the image to open in full size.
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Old 22nd October 2007, 04:42 AM   #1937
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Default Found it

Nevermind.....duh. One whole bank of my rectifier diodes is backwards. How amateur is that.
Robert
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Old 22nd October 2007, 05:15 AM   #1938
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Default All Good

Okay....I re-installed the diodes in the correct orientation, and pirated another C3 from my next kit.....listening to Pink Floyd right now from the DAC to a Mini3 to some Sennheisers.....sounds awsome! Very good response at both ends. I did use Caddock TF020s and 2.2uf film capacitors at the outputs because I had tried that on the NOS DAC, and found I liked the high end better.

There doesn't seem to be any permanent damage to anything except C3, but is there anything else I should check?

Peter, I could use another C3....just tell me how much to PayPal you if you have any extras.
Thanks
Robert
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Old 24th October 2007, 06:13 AM   #1939
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Default 2nd One

I just finished up my second USB DAC PCB, and it works perfectly. I also realized I had replaced R8 & R9 Rikens with Caddock TF020s instead of R7 and R9. So I got those three resistors all sorted out on both boards....they sound even better now....a little smoother. To fit the Caddock at R7 without having it protrude on the bottom of the board, I swapped board sides with R8 and R7.

R7 and R9 are the correct ones to replace....correct Peter? I noticed you added the Caddock-spaced thru hole pads at R8 and R9, but not R7, and it threw me off a little.

I'm planning to build two more boards without the PSU section, or at least without the inlet and transformer, and put them into the cases I built for my two NOS DACs, sharing one PSU switched between the two DACs in each case.

It looks like the PCB cut could be made to feed the second board from the first transformer secondary (so the PSU diodes, caps and inductors would be duplicated); or you could cut it right behind the inductors and make the connection at R1,2,3,4 (so none of the PSU would be duplicated). To switch the PSU between the two boards would require a 4PDT switch? Any suggestions?

Peter I've also emailed you directly regarding buying another C3 to replace the one I toasted when my rectifiers were reversed.
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Old 25th October 2007, 01:46 PM   #1940
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Default Re: All Good

Quote:
Originally posted by rjkdivin
Peter, I could use another C3....just tell me how much to PayPal you if you have any extras.
Sorry for late reply, but I was away. No problem with another C3, however, you might consider that such "cooked" capacitors may actually sound better

http://www.goodsoundclub.com/GetPost...&Phrase=cooked
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