I have my grandson's amp which he said the blue power light comes on but, he is getting no sound output. from what I've seen on the net. this seems to be a pretty common problem with this amp especially, when being run on 2 ohms which I believe, he said he was doing need to double check with him on that. I also read that Q4901 and Z4901 were good possibilities to check I snipped the leads on Q4901 to test and tested Z4901 in circuit using diode check and both checked fine. I also, read that Q4901 normally runs very hot so, I hope not hot enough to melt solder after I re-solder the pins back together on it. 
I have a Corsair TX 850 watt peak, 50 amp single 12v rail ATX PS. would that be good enough just to make voltage checks in the amp or would I be better off to remove the board and just test components without power so I don't risk burning up any of them due to not being clamped to their heatsinks? All advice would be greatly appreciated, I have no scope just a digital mm. Fluke 87V.
I have a Corsair TX 850 watt peak, 50 amp single 12v rail ATX PS. would that be good enough just to make voltage checks in the amp or would I be better off to remove the board and just test components without power so I don't risk burning up any of them due to not being clamped to their heatsinks? All advice would be greatly appreciated, I have no scope just a digital mm. Fluke 87V.
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An oscilloscope is needed to see what the oscilators are doing and to check the dead time on class D amplifiers. However, it is good practice to test the output transistors first for short circuits. This can be done whilst still mounted on the boards. If none are faulty, check the power supply. A 12Volt 10Amp power supply should be OK if no audio is reunning through the amp and no load, to test the internal power supply. I use a motorcycle battery.
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