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Old 23rd December 2012, 10:50 PM   #1
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Default SIT Startup Problems - What did I miss?

I built the original circuit exactly as pictured here:
Click the image to open in full size.




I need help here figuring our what I missed when wiring my SIT.

Observations:

All four lamps light up what appears to be correctly and they increase or decrease in brightness when I adjust P1 on either channel. I also have an ammeter in line with the main power circuit so I can see current increase and decrease when P1 is adjusted.

Problem:

When drawing 2 amps bias I have 25vdc on the speakers terminals. If I increase the bias to 2.6 amps I get 8VDC on the speaker terminals.

Thoughts anyone?

Regards,
Dan
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Old 23rd December 2012, 10:56 PM   #2
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Strange. I measured the DC voltage on both sides of C6. It's the same voltage on both side of the capacitor. Hmmmm................

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Dan
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Old 23rd December 2012, 11:37 PM   #3
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Bad cap, reversed cap or mis-wiring.

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Old 23rd December 2012, 11:57 PM   #4
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besides bad cap , there is missing bleeder resistor on speaker side

that's the price when Pa is in a hurry to please everyone

it can be a problem when connecting speaker to still excited cap
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Last edited by Zen Mod; 23rd December 2012 at 11:59 PM.
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Old 24th December 2012, 12:14 AM   #5
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Slipped in a spare 47000uF/25v electrolytic and got the same results. My current vote goes to some sort of miswiring. Bias circuits and main PS supply circuits seem to be behaving 'normally' so I'm inclined to look elsewhere. Since both channels are consistent I think it's safe to assume I made the identical mistake in both channels. Hmmmmm........

Regards,
Dan
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Old 24th December 2012, 12:15 AM   #6
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Was that my schematic?

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Old 24th December 2012, 12:37 AM   #7
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally Posted by Nelson Pass View Post
Was that my schematic?

bad Pa ;

'twas your blessing

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Old 24th December 2012, 12:39 AM   #8
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Quote:
Originally Posted by dantwomey View Post
Slipped ....
pics are your friend ;

not just those from Playboy , when you were a teen , but also ones posted on forum , as additional info

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Old 24th December 2012, 12:42 AM   #9
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Quote:
Originally Posted by Zen Mod View Post
pics are your friend ;

not just those from Playboy , when you were a teen , but also ones posted on forum , as additional info


Built the identical circuit as displayed in the first post. Thinking.............

Click the image to open in full size.

Regards,
Dan

Last edited by dantwomey; 24th December 2012 at 12:45 AM.
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Old 24th December 2012, 12:54 AM   #10
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With C6 disconnected what voltage should I get from D to ground?

Regards,
Dan
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