I have NAD S300 amplifier and want to know current of output transistors.
Service manual says this:
Connect a digital millivoltmeter between TP301 and TP303, and adjust P501 to
obtain a reading of between 30mV and 35mV.
But in other place of service manual I can see this:
Adjust P501 for 75mV between TP301 and TP303.
Which of these variants is right?
Service manual says this:
Connect a digital millivoltmeter between TP301 and TP303, and adjust P501 to
obtain a reading of between 30mV and 35mV.
But in other place of service manual I can see this:
Adjust P501 for 75mV between TP301 and TP303.
Which of these variants is right?
If You are absolutely sure of the TPs, I would go for the later.
Perhaps You can tell us what value there is on the emitter-resistors in this amp?
Perhaps You can tell us what value there is on the emitter-resistors in this amp?
And are these test points across one or both of these resistors ?
Even taking the "best case" of 35mv across 0.3 ohms it still works out at 116ma which is high.
It would help to see the circuit or at least the output stage. Is it FET or bjt ? Emitter follower or CFP type output.
Post a snippet showing the output transistors and resistors 🙂
Even taking the "best case" of 35mv across 0.3 ohms it still works out at 116ma which is high.
It would help to see the circuit or at least the output stage. Is it FET or bjt ? Emitter follower or CFP type output.
Post a snippet showing the output transistors and resistors 🙂
These test points are across both of these resistors.
Emitter follower with 2 pairs of Sanken.
S300 have huge radiators and I think current should be higher than 53ma on one Sanken.
Maybe someone have this amplifier and can measure current of output transistors?
Emitter follower with 2 pairs of Sanken.
S300 have huge radiators and I think current should be higher than 53ma on one Sanken.
Maybe someone have this amplifier and can measure current of output transistors?
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It's because it don't use overall feedback, so a high bias current help to keep output impedance low and distortion "aceptable"... 😉
Hi! I have restored a NAD S300 and i have questions about the bias settings...
I have tuned it to 35mV (117mA 0,15+0,15=0,30ohm)
What i heard people say this unit runs very hot after idling some hours...
In the service manual it say two different settings 35mV and 75mV.
When it was relesed it had issues in the gain stage, and later NAD came with a "uppgrade" to lower the temperature in the E-line gainstage transistors. I suppose as well that it even had this higher bias setting (75mV). My unit runs "cold" at 35mV maybe around 40'c so it just dont make any sense...
75mV equals 250mA and have to operate in class-A. Are there two types of units out on the market??
I have tuned it to 35mV (117mA 0,15+0,15=0,30ohm)
What i heard people say this unit runs very hot after idling some hours...
In the service manual it say two different settings 35mV and 75mV.
When it was relesed it had issues in the gain stage, and later NAD came with a "uppgrade" to lower the temperature in the E-line gainstage transistors. I suppose as well that it even had this higher bias setting (75mV). My unit runs "cold" at 35mV maybe around 40'c so it just dont make any sense...
75mV equals 250mA and have to operate in class-A. Are there two types of units out on the market??
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