Hi guys
I've had an A60 for about 25 years. Suddenly today it has no phono stage output. Phono is ok, tested on another system so it's the amp. I'm not sure where to start on the A60. Can you give me some advice as to where to start please. A novice with amps.
Cheers
I've had an A60 for about 25 years. Suddenly today it has no phono stage output. Phono is ok, tested on another system so it's the amp. I'm not sure where to start on the A60. Can you give me some advice as to where to start please. A novice with amps.
Cheers
Found schematic here: Arcam A60 upgrade pictures.
Anyway the first thing is disconnect speakers and try measuring the output DC offset voltage on each channel. If its not small (<1V) the speakers would be in danger.
If its totally silent then the main fuse might have gone, easy to check this.
Or internal fuses could have blown, which means disconnecting mains power and opening the case and having a look. Worth looking for any signs of heat damage or bulging capacitors too while at it.
Fuses normally blow for a reason though, so just replacing them isn't sensible.
If its not fuses and if you're happy to work on the amp while powered up the next step is checking the main power supply rails are at correct voltage.
It likely has a protect circuit and relay and this could be active and holding the speakers disconnected. Sometimes the electrolytic caps in the protection circuit fail enough to trigger protection mode falsely.
Anyway the first thing is disconnect speakers and try measuring the output DC offset voltage on each channel. If its not small (<1V) the speakers would be in danger.
If its totally silent then the main fuse might have gone, easy to check this.
Or internal fuses could have blown, which means disconnecting mains power and opening the case and having a look. Worth looking for any signs of heat damage or bulging capacitors too while at it.
Fuses normally blow for a reason though, so just replacing them isn't sensible.
If its not fuses and if you're happy to work on the amp while powered up the next step is checking the main power supply rails are at correct voltage.
It likely has a protect circuit and relay and this could be active and holding the speakers disconnected. Sometimes the electrolytic caps in the protection circuit fail enough to trigger protection mode falsely.
OP talked about "no phono stage output" - may we suppose high level inputs and power amp are working ?
Thanks guys. Just to clarify, other inputs are working correctly and sound OK, it is just the phono stage with no output. Cheers
Phono Mag input shares 34 volts supply, reduced to 15 by Q201,
with the rest of the preamp.
There is only a single resistor for decoupling : R201 1k8 ohms.
Check this one and C201 100μF 16V, it my be short.
If this schem is not applicable to your particular amp, let me know.
with the rest of the preamp.
There is only a single resistor for decoupling : R201 1k8 ohms.
Check this one and C201 100μF 16V, it my be short.
If this schem is not applicable to your particular amp, let me know.
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Full set of schematics for various editions of this amp is on HiFiengine -
registration required.
You will see quite a few phono amps and different supplies.
registration required.
You will see quite a few phono amps and different supplies.