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What might be wrong?

docstocker

docstocker

pfm Member
I recently tried to put together an old system for my son. Trying it out at home, before organising to take it to his new house.
System is a Thorens Td150, basic arm, AT95E, NAC 42-5 and Nap 110. Hasn't been used for a few years.
To my horror, once set up, all I got from both speakers, was a loud popping sound at approx 180/minute. This was without any input or signal. without running the turntable. Not sure where to start and trying to isolate the offending item, I started by substituting the Nac 42.5 into my own system in place of my NAC 32.5 but obtained the same result. This seems tome to suggest that it is the pre amp at fault.
Looking inside, there does not seem to be anything leaking. The only change since I last set this system up is the addition of a pair of RSL MM phono cards. Previously it had only been used with CD and streaming.

I am reluctant to experiment further. Unless anyone has a better idea, I think I had better ship this off for a service. Is Mark still doing the servicing at Witch Hat?.

John
 
I was about to suggest that you took all the cards out, but I think the 42.5 has active circuits on the main PCB and just the phono cards are replacable. Assuming the issue isn't just with the phono input and assuming the voltage source for the 42.5 when in your system was the one you use for the 32.5 then the fault lies with the preamp main PCB - odd that it's affecting both channels - try it without the phono cards, and make sure the +24v coming out of the 110 is ok. If it's still doing it, then there is a problem on the main PCB, possibly power supply rail, but it shouldn't be a difficult or expensive repair (unless you sent it to Naim!).
 
Without connecting the 110 to the 42 or loudspeakers check the 24.7v dc output from the regulator via the 4 pin socket on the 110.
 
I had the same with some equipment that hadn’t been used for years. Cured by cleaning the din lead from pre to power. And the din sockets on both. I had some deoxit cleaner - worked perfectly...
 
If you're using the 4 pin socket have you checked that the 5 pin socket has the "bridging" plug fitted. I think that the 42.5 power supply is split front to back -- one supply to the phono boards and the other the main pcb -- so whatever's wrong will affect both channels. If the plug is missing you might try something like a paper clip between the 2 24v pins in the din socket as a (very) temporary trial.
Regards,
Steve
 
Thank you everyone
I am going to try these ideas before sending the offending item for a service.
In the meantime the Td150/basikplus/AT95E is sounding very good through my CBNait into mission 752 loudspeakers
I also got to see and cuddle my six week old granddaughter, so yesterday was a very good day indeed
John
 
From experience I'd recommend Darran at Class A for servicing Naim gear, he's recommended by Naim and less expensive. Good luck with the 42/110, a great little combo plain or .5 with or without snaps or HiCap.
 
Came across this thread and thought I would update as it might help some one else.
I opened up the case and found one phono card not fully in place. I also cleaned all the contacts of the leads between the boxes and when re assembled sounded very good again.
Thank you everyone
 
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