Apex AA14 Amp Class A 24V Supply

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#61
minek123 said:
How C12 can be 0.9V ? That should be rail voltage +20V.
What PSU are you using? What current amp draws without output devices?

Is your positive rail voltage going to 0.9V on idle amp that doesn't even draw significant current?

I'm assuming LOW current, so the positive rail shouldn't sag, and Voltage on C12 should show +20V (or whatever your voltage supplies exactly are, little bit over 20V I guess).
Click to expand...
ah...typo...sorry is bad if i missreading..

C12 is wrong! it is C10

if i desolder C6 should i measure?
 
#68
here is the actual "setup" 🤣
 

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#70
T1 needs biasing - usually it's R from the base of T1 to the GND.
Here R5 is connected to ground via R8, so some part of the feedback AC signal will be send to T1 (besides T5).
I've seen this before on some amps, but not sure what problem exactly it's trying to solve....
Value of R5 usually is similar (or the same) to R10 (feedback resistor).

Diode D1 is supposed to clamp IPS differential output voltage to prevent saturation of the current mirror (T2/T4) when the amp clips.
Usually there is 2 diodes in parallel, in opposite directions.
 
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#72
omg 🙄

i de solder D1 and T5 both components are checked and fine
C6 is out

all measurements from GND

now i get - 22.4 DC offset on the speakers and on the base of T5 too???!!!
T5 GND to Base -22,4V
T5 GND to Collector-22,9V
T4 GND Collector -22.9V
T2 is off
R3+R6 no Voltage
T1 GND Emitter -13,9V
R5 zero Volt

What??
 
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