I have a Meridian 557 that I bought new with a balanced Meridian stack around 1998 (502, 500, 566-24, 557) but it's refusing to power up now. It goes through the soft start sequence, stays on for a couple of seconds then you hear one of the protection relays click and it does a power down. I haven't been able to find a Meridian expert that knows their classic audio components in the Seattle area and the local "official Meridian support" folks are a home theater showroom/installation place that thought I was confused because they didn't know what a 557 was.
I had the local MacIntosh expert check it out for me (reluctantly) and he said the bias is too high on the right channel and that is what is causing the shutdown to trigger. He said it appears to have an auto bias system with no settings (does anyone know if that's true?). He was pretty impressed once he opened the top and said he could probably fix it but would need to see a schematic first. I have found a Meridian 556 schematic but no 557 schematic.
Has anyone seen an issue similar to this in the past and hopefully know what the cause is? I'm an EE/CS with some analog knowledge but I would not attempt to repair this myself. However, I can pass along any detailed information to Mr. MacIntosh who has 25+ years experience fixing high quality amps and other components.
Thanks,
Dean
I had the local MacIntosh expert check it out for me (reluctantly) and he said the bias is too high on the right channel and that is what is causing the shutdown to trigger. He said it appears to have an auto bias system with no settings (does anyone know if that's true?). He was pretty impressed once he opened the top and said he could probably fix it but would need to see a schematic first. I have found a Meridian 556 schematic but no 557 schematic.
Has anyone seen an issue similar to this in the past and hopefully know what the cause is? I'm an EE/CS with some analog knowledge but I would not attempt to repair this myself. However, I can pass along any detailed information to Mr. MacIntosh who has 25+ years experience fixing high quality amps and other components.
Thanks,
Dean
I have found a schematic for the 557 so hopefully this will help. However, if anyone has seen a problem like this where the amp shuts itself down within a couple of seconds after power up, it would be very helpful for the guy who is working on this for me. He is the local MacIntosh tube/solid-state expert but hasn't worked on Meridian.
If you have the actual 557 schematic could you post it or a link to it ?
Forget the name-tag its just another safety relay operating because of fault conditions in a power amplifier of one sort or another .
You could start with the output devices for faults or components round them , if not work your way back ,if its chip controlled check that or round about it.
DIY Audio is full of this type of fault ---amazingly none of the power amplifiers I built have safety devices apart from one of JLH,s mosfet stabilized power amp designs and even there he changed the BJT pass device for mosfets.
Either designs have gone down in reliability / component quality isn't good or some users have "lead fingers " /accident prone as the stuff I built or designed is still working.
Forget the name-tag its just another safety relay operating because of fault conditions in a power amplifier of one sort or another .
You could start with the output devices for faults or components round them , if not work your way back ,if its chip controlled check that or round about it.
DIY Audio is full of this type of fault ---amazingly none of the power amplifiers I built have safety devices apart from one of JLH,s mosfet stabilized power amp designs and even there he changed the BJT pass device for mosfets.
Either designs have gone down in reliability / component quality isn't good or some users have "lead fingers " /accident prone as the stuff I built or designed is still working.