Here is the voltages from 1 amp board, and yes both are doing the exact same thing. I have ordered KSC3503D from digikey to swap out the 2SC3503 to see if that makes a difference. With no load the amp still will not go full rail voltage, the scope behavior is the same as with the load like the image I posted before.The gain on that looks a bit low (I get ~108). But, you also don't know how the device is behaving as the Vce increases as ther amp output swings between the two rails. The +ve side spike almost loops like the device is 'snapping' to some kind of short circuit mode.
I earnestly recommend that you never ever buy parts off eBay - always stick to mainstream disti's like Mouser, Digikey, RS etc. You do pay more, but you know what you are getting.
Below is a circuit diagram - you should check all your quiescent DC voltage against this with no input signal.
If the voltages are all ok, try please try this:
1. Connect the PSU to the amp (especially the Zobel connections - do not leave these off. Make sure the wires to and from the amp module are tightly bundled together
2. Run the amp with no load and a 1kHz input signal and see if it swings up to the rails - if it does, I would suspect the driver gains are dropping off at higher currents load currents. Check the 0 Ohm jumpers - make sure they are 0 Ohms and have not been damaged and gone high R during assembly.
Come back and let us know what you have found (are both channels behaving like this?)
Thanks!
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Yeah so how were the voltages? Should I just wait now to swap the transistor?The DC offset will typically settle to within a few mV of 0 V after about 2-3 mins.
Thanks, here is the voltage drops;The voltages so far look ok. Can you check the voltage drop across R22 and R23 and R30 and R31.
R22 - .542
R23 - .542
R30 - .400
R31 - .401
VAScurrent=26mA?Thanks, here is the voltage drops;
R22 - .542
R23 - .542
R30 - .400
R31 - .401
Thermal compound as recommended to help bias track with temp.
Any thoughts on what I should check next?They look like NTC’s to me. I should have said something earlier about it.
I will have one today. What voltages should I test at and what I'm I looking for. Thanks!I think the only way we can try to get to the bottom of this is to inject a DC input and look at the amp voltages with no load connected to the output.
Have you got a lab PSU where you can adjust the voltage that we can use to inject a DC signal?
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