Ummm that was from a very tired memory scratch that last reply:
The board is configure on the connector front to back as E C B . The MPSA6521 is E B C . I flipped legs 2 and 3. Draws 2.4A at idle until RCA is plugged in and then drops to 1.16A. Bias adjust not possible in that channel. On the connector shown in the picture in previous post pin 1 being the front of the amp (emitter as I think its is) I have :
pin 1 (E) -4.95V
pin 2 (C) .256V
pin 3 (B) -4.32V
The board is configure on the connector front to back as E C B . The MPSA6521 is E B C . I flipped legs 2 and 3. Draws 2.4A at idle until RCA is plugged in and then drops to 1.16A. Bias adjust not possible in that channel. On the connector shown in the picture in previous post pin 1 being the front of the amp (emitter as I think its is) I have :
pin 1 (E) -4.95V
pin 2 (C) .256V
pin 3 (B) -4.32V
Q110 was once again out of spec. Replaced. Audio is now not distorted. Bias is adjustable. But amp still draws 2A at idle until RCA's are plugged in then amp goes to 1.1A. Is this normal?
That's not leg 1-3, that's referenced to ground.
It appears that you have 3.6v across the gate and source of the N-channel FET. Confirm with the probes on those two terminals. I would expect that you would have significant DC offset toward the negative rail. Are you sure that the FETs are good?
It appears that you have 3.6v across the gate and source of the N-channel FET. Confirm with the probes on those two terminals. I would expect that you would have significant DC offset toward the negative rail. Are you sure that the FETs are good?
I confirmed and that is the case. It reads exactly the same on all other channels on the amp. At speaker out terminals there is no significant dc offset. These FET's straight from Future Electronics. Rcas plugged in same as they are unplugged except the amplifier draws 2 amp idle.. Weird... Amps plays clean audio. I'll put a 1000Hz wave and look at the scope.
Do you see a change in rail voltage or a change in the pulse width at the gates of the FETs when you plug the RCAs in?
If I measure it correctly I'm not really seeing anything significant. Amplifier plays and seems to work perfectly otherwise. No RCA plugged in and grounding the shield at the input jack makes a changed in Idle current (1.84A) but not as significant as completely plugging in the RCA. If amplifier is playing is this really going cause a problem, as the RCA's are always plugged in anyway?
It probably isn't a significant problem.
Does it make a difference if you set the crossovers to low pass?
Does it make a difference if you set the crossovers to low pass?
Any of the switch make no difference. I operated everything in the full range while watching the readout closely. Not even the 2ch/4ch switch. I left it on the bench playing 4 ohm all channels driven and its playing great. He'll who knows. Probably test it in my car on the way out of town tomorrow. Thanks Perry.
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