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-   -   SIT Startup Problems - What did I miss? (http://www.diyaudio.com/forums/pass-labs/226319-sit-startup-problems-what-did-i-miss.html)

dantwomey 23rd December 2012 09:50 PM

SIT Startup Problems - What did I miss?
 
I built the original circuit exactly as pictured here:
http://i964.photobucket.com/albums/a...hemptone-1.jpg




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 :(

dantwomey 23rd December 2012 09:56 PM

Strange. I measured the DC voltage on both sides of C6. It's the same voltage on both side of the capacitor. Hmmmm................

Regards,
Dan :(

Nelson Pass 23rd December 2012 10:37 PM

Bad cap, reversed cap or mis-wiring.

:cool:

Zen Mod 23rd December 2012 10:57 PM

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 :clown:

dantwomey 23rd December 2012 11:14 PM

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........:confused:

Regards,
Dan :hohoho:

Nelson Pass 23rd December 2012 11:15 PM

Was that my schematic?

:cool:

Zen Mod 23rd December 2012 11:37 PM

Quote:

Originally Posted by Nelson Pass (Post 3297145)
Was that my schematic?

:cool:

bad Pa ;

'twas your blessing

:rofl:

Zen Mod 23rd December 2012 11:39 PM

Quote:

Originally Posted by dantwomey (Post 3297140)
Slipped ....

pics are your friend ;

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

:devily:

dantwomey 23rd December 2012 11:42 PM

Quote:

Originally Posted by Zen Mod (Post 3297164)
pics are your friend ;

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

:devily:


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

http://i964.photobucket.com/albums/a...womey/4601.jpg

Regards,
Dan :hohoho:

dantwomey 23rd December 2012 11:54 PM

With C6 disconnected what voltage should I get from D to ground?

Regards,
Dan


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