Hi All
I have a NAD L75 small format surround receiver that I use as a 2-channel amplifier for my PC speaker setup.
It has developed an issue when powering on the unit. You can hear one of the relays clicking away multiple times but the amp does not immediately switch on. Sometimes after just a few relay 'clicks', sometimes many clicks that could last a minute or two, the unit does eventually power on and there are no operating issues from then on; everything seems to work fine. Often if you turn the unit off again and then back on it will turn on fine without issue. If it's left for a few days then it's highly likely to have the initial startup issue again. Recently this was also accompanied by some popping from the speakers while it was trying to power on so I'm not sure if this is a related issue or not. There is a second relay click a second or two after the unit powers on which I assume is the speaker protection circuit. Another possible clue is that the display when in standby mode [it just shows the time] is very dim and flickers on and off. Once the unit powers on, the display works as normal.
Below is a link to the service manual with schematics:
https://www.manualslib.com/manual/1422086/Nad-L75.html
I isolated the clicking relay at startup to the "AC Outlet PCB - KUP11431-2" RY91 - BSL1A008ZE - RELAY - SDT-S-112DMR and thought that may have been the issue so I replaced it which made no difference at all.
There are no obviously swollen caps that I can see, no burnt components etc. I'm assuming that the issue lies somewhere in the initial power supply boards before all the amplifier, decoder etc. but I'm a bit out of my depth as to what it could be. If anybody can assist and give me some direction on what the issue could be... I'm more than capable with a multi-meter, soldering iron etc. so fixing the issue shouldn't be too hard if we can work out what it is!
Thanks
Dave
I have a NAD L75 small format surround receiver that I use as a 2-channel amplifier for my PC speaker setup.
It has developed an issue when powering on the unit. You can hear one of the relays clicking away multiple times but the amp does not immediately switch on. Sometimes after just a few relay 'clicks', sometimes many clicks that could last a minute or two, the unit does eventually power on and there are no operating issues from then on; everything seems to work fine. Often if you turn the unit off again and then back on it will turn on fine without issue. If it's left for a few days then it's highly likely to have the initial startup issue again. Recently this was also accompanied by some popping from the speakers while it was trying to power on so I'm not sure if this is a related issue or not. There is a second relay click a second or two after the unit powers on which I assume is the speaker protection circuit. Another possible clue is that the display when in standby mode [it just shows the time] is very dim and flickers on and off. Once the unit powers on, the display works as normal.
Below is a link to the service manual with schematics:
https://www.manualslib.com/manual/1422086/Nad-L75.html
I isolated the clicking relay at startup to the "AC Outlet PCB - KUP11431-2" RY91 - BSL1A008ZE - RELAY - SDT-S-112DMR and thought that may have been the issue so I replaced it which made no difference at all.
There are no obviously swollen caps that I can see, no burnt components etc. I'm assuming that the issue lies somewhere in the initial power supply boards before all the amplifier, decoder etc. but I'm a bit out of my depth as to what it could be. If anybody can assist and give me some direction on what the issue could be... I'm more than capable with a multi-meter, soldering iron etc. so fixing the issue shouldn't be too hard if we can work out what it is!
Thanks
Dave
Other than the usual checks for bad solder joints and a measurement of all power supplies, I don't have any specific suggestions.
Relay RY91 seems to be controlled by a signal from the microprocessor called "power_on". Since you already eliminated the relay, I guess now is the time to try to find the cause of why the processor shows this erratic behaviour. I have not looked at lengths at the schematics, but it looks like the AC out isn't equipped on all versions, so it may not strictly be needed for operation. Having said that, I don't know if the symptom may have an affect on other parts of the circuit preventing normal start up. That's for you to find out.
Relay RY91 seems to be controlled by a signal from the microprocessor called "power_on". Since you already eliminated the relay, I guess now is the time to try to find the cause of why the processor shows this erratic behaviour. I have not looked at lengths at the schematics, but it looks like the AC out isn't equipped on all versions, so it may not strictly be needed for operation. Having said that, I don't know if the symptom may have an affect on other parts of the circuit preventing normal start up. That's for you to find out.
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