I have two Arcam Alpha 10 Amps.
The FISRST ONE:
It works fine on headphones on both channels but I get no audio on Right Channel on both speakers SP1 and Sp2.
Where shall I start looking for faults please?
The MOFSETs seem fine.
The SECOND ONE:
The amp very briefly powers up and displays for less than a second and then it shuts down.
It had two MOFETS shot ( zero reststance ) on SP1.
SP2 MOFSETs are ok
I removed the two faulty MOFSETs from SP1 and powered it up, it stayed on for 5-6 seconds but I culd start see smoke from one of the resistor.
If I replace the MOFSETs could it fix the issue?
I'm wondering if you remove the MOFSETs from one set of speakers shouldn't really the amp stay on but not burning anything?
( Service Manual Attached )
Thanks
The FISRST ONE:
It works fine on headphones on both channels but I get no audio on Right Channel on both speakers SP1 and Sp2.
Where shall I start looking for faults please?
The MOFSETs seem fine.
The SECOND ONE:
The amp very briefly powers up and displays for less than a second and then it shuts down.
It had two MOFETS shot ( zero reststance ) on SP1.
SP2 MOFSETs are ok
I removed the two faulty MOFSETs from SP1 and powered it up, it stayed on for 5-6 seconds but I culd start see smoke from one of the resistor.
If I replace the MOFSETs could it fix the issue?
I'm wondering if you remove the MOFSETs from one set of speakers shouldn't really the amp stay on but not burning anything?
( Service Manual Attached )
Thanks
I need to power it up to see exactly where the smoke is coming from but I am a bit reluctant to do so just in case I damage it even further. I'll put a picture shortly
One of those top left resistors looks burned. They may be these.
That may be because with the FET's removed the feedback loop is broken and all DC conditions change. Would it work with new FET's its hard to say as there may be collateral damage around the driver transistor stages.
That may be because with the FET's removed the feedback loop is broken and all DC conditions change. Would it work with new FET's its hard to say as there may be collateral damage around the driver transistor stages.
Ok just bought some replacements from Mouser they will come next week I will test and find out.
Any thoughts on the first one?
I’ve actually got 4 of them !
Any thoughts on the first one?
I’ve actually got 4 of them !
Check the basic DC conditions on the faulty channel such as DC offset and correct output stage bias current. If those are good the amp is basically operational. Check continuity including any speaker relays etc from output to speaker socket.
If that doesn;t prove anything then you need to use a scope and confirm the audio input signal is actually reaching the input to the faulty channel power amp.
If that doesn;t prove anything then you need to use a scope and confirm the audio input signal is actually reaching the input to the faulty channel power amp.
