Just curious which amp did you pull that driver board from? Im keeping notes on the r44 and r36 resistors.
Aren't those chosen, to some degree, on rail voltage?
If you're using generic replacement boards, R30 is also an issue.
If you're using generic replacement boards, R30 is also an issue.
Both are 2.4k!
Can you explain better please?Perry Babin said:
If I am not mistaken R30 is used in the circuit that operates the overload protection. From what I know (and what I understand by looking at the schematics of some amplifiers that use this driverboard) the only thing that establishes the protection threshold is the value (and therefore the number) of shunts used to monitor the load on the output mosfets. I think the R30 is always 3.3k, or am I wrong?
R36 and 44 vary. They are not always (or have not always been) the same value. I've seen 2.4k and 3.3k.
R30 also varies. The threshold point must coincide with the voltage across the shunt resistors at a specific current flow to trip the over-current protection at a safe amount of current flow. If the shunt resistors or the safe current flow varies from one amp to another, the corresponding threshold resistor may need to be adjusted. I've seen both 270 ohm and 330 ohm in the 4070 boards. In smaller boards (non-21844), 270-390 ohms.
R30 also varies. The threshold point must coincide with the voltage across the shunt resistors at a specific current flow to trip the over-current protection at a safe amount of current flow. If the shunt resistors or the safe current flow varies from one amp to another, the corresponding threshold resistor may need to be adjusted. I've seen both 270 ohm and 330 ohm in the 4070 boards. In smaller boards (non-21844), 270-390 ohms.
Oh, of course! my mistake...
330ohm, not 3.3k, yes, but in years, i've never seen before 270ohm.
Same thing with r36 & r44, i've seen always 2.4k, rarely 2.7k but never 3.3!
very strange.
Another thing, R1 - R40 - R41 - R31 sometimes 10k and sometimes 15k (deadtime setting).
330ohm, not 3.3k, yes, but in years, i've never seen before 270ohm.
Same thing with r36 & r44, i've seen always 2.4k, rarely 2.7k but never 3.3!
very strange.
Another thing, R1 - R40 - R41 - R31 sometimes 10k and sometimes 15k (deadtime setting).
Is not the same diode, but probably work good.
Usually, even if only one Vb diode is shorted, i change always all 4.
Matched components are better.
Usually, even if only one Vb diode is shorted, i change always all 4.
Matched components are better.