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QUDOS - the brilliant new amplifier boards from Avondale

Chops54 said:
For initial testing without the output transistors, does the BD237 need to be in circuit?
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I didn't explain myself too well there I'm afraid. I've already put a 2N5551 in the T5 slot without thinking about it. I was going to remove it but as I haven't any BD237s yet I can just leave it like it is and carry on for the moment?
 
With all transistors removed and power applied I have readings across the 220R resistors feeding the input stage of 2mv positive and 276mv negative. Does this show a problem?
 
S-Man said:
Yes (must admit I wondered why you would want to run it without the Vbe multiplier).
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I hadn't actually thought of doing that at all but a combination of meds and tiredness is starting to muddy the waters I'm afraid. Maybe I shall have to restrict my posting until such times as I'm a bit more with it lol.
 
Not sure where the few uA in the positive supply are flowing - probably a bit of leakage in one of the caps, which is OK.
The 1.2mA in the negative supply is through the 22K bias resistor that feeds the 2 1N4148s, which implies your supply voltage is about -28V.

So, seems OK.
 
Chops54 said:
I hadn't actually thought of doing that at all but a combination of meds and tiredness is starting to muddy the waters I'm afraid. Maybe I shall have to restrict my posting until such times as I'm a bit more with it lol.
Click to expand...

No, it was my misunderstanding!
It's so easy to get the wrong end of the stick when reading posts. :confused:
 
S-Man said:
Not sure where the few uA in the positive supply are flowing - probably a bit of leakage in one of the caps, which is OK.
The 1.2mA in the negative supply is through the 22K bias resistor that feeds the 2 1N4148s, which implies your supply voltage is about -28V.

So, seems OK.
Click to expand...

Many thanks.
 
No worries S-Man, it's not your fault I decide to post when I'm not with it. I'd have been lost at sea a few times without the help I've had from members of this forum and it's always appreciated.
 
As far as I'm aware there's only been one version of the NCC220 (Qudos) boards, I've started a conversation and sent the circuit diagram to Chops54
 
I believe that I may finally be getting somewhere with my second board. Having changed the transistors; even though they measured ok on the Atlas I am now able to set the voltage across tp3/4 to 1.65V and having 2.5V across the 220R resistors I think I am good to go. No magic smoke so will solder in the output trannies this evening.
 
Marra said:
I believe that I may finally be getting somewhere with my second board. Having changed the transistors; even though they measured ok on the Atlas I am now able to set the voltage across tp3/4 to 1.65V and having 2.5V across the 220R resistors I think I am good to go. No magic smoke so will solder in the output trannies this evening.
Click to expand...

Good news...
 
Thanks Graham. The amp has been ticking over with the bias set at 12.7ma for a couple of hours so music time later this morning,
 
Big grin time!! We have music.

Many thanks to those who offered advice and in particular LesW who made this excellent amp available to we diyers.
 
I know a few of you built NCC200s with BUV20 output devices so has anyone done a comparison between that and the NCC220?
 
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