Super Regulator

[jan.didden]

Still don't understand why the base of Q1 can be almost ground, and the emitter/output 14V.
Which transistor type did you use for Q1?

Jan

 

[buzzforb]

D44h11 and its compliment on negative side

 

[jan.didden]

Got to go but will be back tonight (couple of hours).

Jan

 

[buzzforb]

Pic

 

[buzzforb]

I appreciate the help. Every time I think I have learned a little, something like this happens.

 

[Salas]

Is it compatible with floating mid-point raw DC?

 

[Salas]

Are the sense connections set for closing the test circuit?

 

[buzzforb]

I had this thought as well Salas, but initially it was connected at the riaa board and yielded same results. All sense connections are closed and each board has a 500 ohm load across outputs.

 

[jan.didden]

The thing is, the base of the pass Q1 is at gnd and Vout is 14V. WTF??

Did you remove Q2, did the LED light up?

Edit: each board is fed from a separate isolated xformer winding through its own rectifier and cap? No connections whatever between the two raw supplies?

Jan

 

[buzzforb]

With q2 removed, the LED lights up. The rectification arrangement can be seen in pic. Common ground is created after the cap in pre filter.

 

[jan.didden]

Still 14V out?

 

[buzzforb]

yup. No change otherwise. not by the circuit at the moment. FWIW, I tested diode junction of the pass bjt's and it was good.

 

[jan.didden]

yup. No change otherwise. not by the circuit at the moment. FWIW, I tested diode junction of the pass bjt's and it was good.

And the base of the pass Q still at Gnd? Can you make sure?

 

[buzzforb]

I will check when I get home this evening.

 

[buzzforb]

Base of Q1 to ground is 6mV. Something has changed. There is no voltage across outputs of regulator

 

[jan.didden]

Finally something that makes sense. ;-)

Now put an R of say 10k from the raw input to the base of the pass Q and see what happens.
Does Vb go up towards 10V or so?

BTW can you double check that the pos pass Q is indeed a D44?

Jan

 

[buzzforb]

Will try when I get back to the boards. Zero doubt the pass transistor is a d44h11

 

[buzzforb]

Vb is 13V and output is 12.5v

 

[jan.didden]

That pass Q looks fully on with base at ground. So it is either broken or there's a soldering short.
Can you check and/or replace?

Jan

 

[buzzforb]

Pass Q replaced. 10k soldered from raw DC to base pin. Raw DC is 15.25V. Base of Q1 is 13.06V