Pumpkin preamp - ordered by Steen , official making thread - Page 316 - diyAudio
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Old 29th December 2011, 10:09 AM   #3151
10y is offline 10y  Italy
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Hi,

I have finished my four shunty and pumpkin boards.

The shuntys work perfectly.

The pumkins have this problem: releved at the output of three of output cap DC wandering under 100 mV. Removed one of the 4,7 uF MKC and with the bypassed little MKC cap DC at output wander around 2 mV.
Tryed other plastic cap and always DC rises proportionally at cap value.

Only one C4 output shows DC zero value

What do you think about that?

Thank you.

Ciao,
Anto
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Old 29th December 2011, 10:11 AM   #3152
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I've got a thread going - Pumpkin Problems - you might like to add your comments there.

My faults have ALL been down to faulty PCBs. Look VERY VERY carefully for minute whiskers of copper.
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Old 29th December 2011, 10:35 AM   #3153
10y is offline 10y  Italy
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Join Date: Feb 2006
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Hi,

I have finished my four shunty and pumpkin boards.

The shuntys work perfectly.

The pumkins have this problem: releved at the output of three of output cap DC wandering under 100 mV. Removed one of the 4,7 uF MKC and with the bypassed little MKC cap DC at output wander around 2 mV.
Tryed other plastic cap and always DC rises proportionally at cap value.

Only one C4 output shows DC zero value

What do you think about that?

Thank you.

Ciao,
Anto
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Old 29th December 2011, 10:40 AM   #3154
10y is offline 10y  Italy
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sorry for the reposting !

For KatieandDad,

I do not thing that my problem is quality pcb related.

Ciao,
Anto
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Old 29th December 2011, 11:20 AM   #3155
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Mine looked perfect too. How different they looked whan looked at under a stong magnifying glass.
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Old 29th December 2011, 11:21 AM   #3156
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I've still got a strange "Whooshing" noise that I can't track down.
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Old 29th December 2011, 11:30 AM   #3157
10y is offline 10y  Italy
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Hi,

Discovered a little shortie at one r29 so relative output was shorted to ground.
Now all four cap output shows DC.
Anto
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Old 29th December 2011, 11:34 AM   #3158
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See what I mean !!!
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Old 29th December 2011, 11:44 AM   #3159
10y is offline 10y  Italy
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yes, but why this DC at output ?
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Old 29th December 2011, 11:48 AM   #3160
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It depends on what R49 was actually shorted to.
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