Need help with Tentlabs power supply

[gy21]

An externally hosted image should be here but it was not working when we last tested it.

I need some help with this power supply. I only get 2.63 V on pin 8.

I feed this circuit with 12.5 Volt, after the 7808 I measure 8 Volts. At the B of the transistor I measeare 3.2V The collectorhas 8 Volts.

If I measure straight over the 22k resistor (not from ground) I get 4,75V. If I measure straight over the 56k resister I get 3,2 Volts Wich is ofcourse the same as the basis at the transistor.

What am I doing wrong here?

 

[poynton]

An externally hosted image should be here but it was not working when we last tested it.

I need some help with this power supply. I only get 2.63 V on pin 8.

I feed this circuit with 12.5 Volt, after the 7808 I measure 8 Volts. At the B of the transistor I measeare 3.2V The collectorhas 8 Volts.

If I measure straight over the 22k resistor (not from ground) I get 4,75V. If I measure straight over the 56k resister I get 3,2 Volts Wich is ofcourse the same as the basis at the transistor.

What am I doing wrong here?

Blown transistor ? Have you tried changing it ?

 

[float]

Just change the 22k for 2.2k and the 56k for 5.6k. That should sort it. Tip courtesy of Guido himself.

HTH

 

[gy21]

Just change the 22k for 2.2k and the 56k for 5.6k. That should sort it. Tip courtesy of Guido himself.

HTH

Yup that fixed it.

Thanks Float!

P.s. I Got 4.6V now, is that close enough to 5 V that is needed for the clock to work correctly?

 

[gy21]

I read on the tentlabs site that the clock needs 5V +-5%. So that means 4,6V is to low.

Any suggestions to raise this voltage? Raising the 5,6K?

 

[float]

I'd adjust the res's to suit; the dac spec calls for 4.7-5.3v.

I got 5.01v when I built mine; maybe the transistor's slightly out of spec?

Also see here http://www.diyaudio.com/forums/showthread.php?s=&threadid=35082&perpage=10&highlight=&pagenumber=1

 

[gy21]

ok, lowered the 2k2 res to a 1k5.

got 5.15 now on pin 8.

that should do it I think.

thanks for your help Float.