Re: Diagnosing NAD receiver -- unexplained shut-downs
I have both, and will take another look, but I didn't see anything obvious. And the orange goo never hit the circuit board (just on the cap itself) and never made it to the side with the traces.
I was so excited when the receiver started up normally after replacing the cap -- and then it died. Could be that the cap I put in got fried within its first use ... or it could be something different....
JordanW
New Member
Last Activity: 02-05-2023, 04:54 PM
Joined: 01-02-2023
Location: Toronto, ON
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Re: Diagnosing NAD receiver -- unexplained shut-downs
An update -- Replacing C712 (the "coin cell" 0.1F cap responsible for maintaining the station memories) got the receiver back into working condition, and I was able to run it for about two hours with totally normal behaviour, including powering it off and on a few times. But after powering it down for the night, it now won't power back on again at all.
I got this receiver for a very low price, second-hand, about 10 years ago, so it doesn't owe me anything!
I'll try replacing that cap again...Leave a comment:
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Re: Diagnosing NAD receiver -- unexplained shut-downs
Sorry for the delay, I wasn't able to get to this until today.
I managed to find C712 on the board. As you suspected -- there is some kind of orange goo emanating from one side (see photo below). I removed it.
The radio doesn't power up at all now, so likely there needs to be something there. I will try to find a replacement tomorrow....Leave a comment:
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Re: Diagnosing NAD receiver -- unexplained shut-downs
I can do that -- just found it on the schematic. That is a big fat capacitance so it should be one of the largest things on the PCB and hopefully easy to find.
I have found that after the power cycles I've been trying out, the receiver "forgets" the last FM station it was tuned to (which I don't recall being its behaviour before) so perhaps that is also a clue in favour of C712 being an issue....Leave a comment:
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Re: Diagnosing NAD receiver -- unexplained shut-downs
Thank you so much for these tips.
In another forum, someone suggested that there may be an issue with D951, D952, D953, D954 (the discrete diodes that make up the bridge rectifier) and / or R951, the resistor that feeds them.
Their thinking is that if one of these diodes is "failing open" as it warms up, or if the resistor is increasing resistance as it warms up, that would explain why the receiver will stay on once powered on, but won't restart once powered down (that...Leave a comment:
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Re: Diagnosing NAD receiver -- unexplained shut-downs
Thanks for the advice. I replaced that cap, and while the radio seems to be behaving a bit better, and will stay on and behave normally for several hours, if I power down the radio it will still not power up again right away -- but will do so after what seems like 30+ minutes "rest".
Any ideas what to try next?...Leave a comment:
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Re: Diagnosing NAD receiver -- unexplained shut-downs
Thanks for the tip, I think the one you are referring to is C951 (the second number does look like a 6 at first) -- 220 uF 16 V capacitor that is part of that standby power supply stage across the four-diode rectifier component, correct?...Last edited by JordanW; 01-02-2023, 02:30 PM.Leave a comment:
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Diagnosing NAD receiver -- unexplained shut-downs
Everyone -- I am trying to troubleshoot my NAD C740 stereo receiver, which either won't power on or won't consistently stay powered on.
I will start by saying that I am a hobbyist, and while I am decently handy with basic DC stuff, I am more hesitant when it comes to mains-powered equipment (that is, reluctant to poke around with a multimeter when it is powered on)
The central issue is that after a long period of non-use, the receiver powers on and all functions seem to behave normally, but after a couple of minutes, it powers itself off.
If I attempt... -
Re: New Members - please post your introductions here
I'm glad I found this forum -- I am looking to repair a 1990s-era stereo receiver that *may* have a bad cap issue (not sure) and look forward to hearing what the experts here have to say about it.Leave a comment:
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