Hello,
I have a problem with my NAD C315BEE amplifier. When I turn it on, using a power switch on the back, I hear a loud Thumb in my speakers. It seems that a protection circuit does not work correctly because at the same time when I turn the rear power switch on a “soft start” relay makes “click” and the mentioned thumb in the speakers appears. I replaced the C334 with bigger one (470uF) but that does not help. I have two questions:
1. Does the protection circuit start counting the delay time from the moment when either the rear power switch is turned on or the power button from the front panel is pressed?
2. What might be root cause of that phenomenon?
Thank you in advance for all your advises.
Rafal
I have a problem with my NAD C315BEE amplifier. When I turn it on, using a power switch on the back, I hear a loud Thumb in my speakers. It seems that a protection circuit does not work correctly because at the same time when I turn the rear power switch on a “soft start” relay makes “click” and the mentioned thumb in the speakers appears. I replaced the C334 with bigger one (470uF) but that does not help. I have two questions:
1. Does the protection circuit start counting the delay time from the moment when either the rear power switch is turned on or the power button from the front panel is pressed?
2. What might be root cause of that phenomenon?
Thank you in advance for all your advises.
Rafal
The NAD C315BEE utilises the UPC1237 protection IC see the data sheet for operation details.
https://pdf1.alldatasheet.com/datasheet-pdf/view/6668/NEC/UPC1237.htmlPin 7 is used to set the time delay C334 should remain 100uf, 16 Volts.
Check components associated with the circuit for CB35 (UPC1237)
https://pdf1.alldatasheet.com/datasheet-pdf/view/6668/NEC/UPC1237.htmlPin 7 is used to set the time delay C334 should remain 100uf, 16 Volts.
Check components associated with the circuit for CB35 (UPC1237)
Hi Audio Service,
thank you for your answer. However, please note that the NAD C315BEE does not use the UPC1237 from NEC. I believe this is a typo in the service manual for the amplifier. In the NAD C315BEE they used kind of discreet solution for protection function - please see the below photo.
As per the provided before DS, the UPC1237 is molded device in plastic package. Please also note that there is no 56kOhm resistor between pin 7 and 8 in the schematic of NAD C315BEE (please see the schematic shown in my first post).
I would appreciate answer on my first question from someone who has that amplifier from NAD. Any other ideas are also more than welcome.
Rafal
thank you for your answer. However, please note that the NAD C315BEE does not use the UPC1237 from NEC. I believe this is a typo in the service manual for the amplifier. In the NAD C315BEE they used kind of discreet solution for protection function - please see the below photo.
As per the provided before DS, the UPC1237 is molded device in plastic package. Please also note that there is no 56kOhm resistor between pin 7 and 8 in the schematic of NAD C315BEE (please see the schematic shown in my first post).
I would appreciate answer on my first question from someone who has that amplifier from NAD. Any other ideas are also more than welcome.
Rafal
Rafal
The C315BEE version that has the surface mounted type protection board is not detailed in the service manual available in the public domain..
An authorised NAD service centre no doubt would have this version of the manual.
To answer your question when the main power from the power transformer is applied the protection circuit is also powered.
After approximately5 - 8 seconds the protection circuit will energise the speaker protection relay.
The time delay allows sufficient time for the large power supply capacitors to charge and eliminates the thud your hear in through the speakers.
The relay should not turn on immediately.
As this version of the protection circuit is using a combination of surface mount and conventional components, you should be able to check and confirm what is causing the issue.
The circuit normally has a charging circuit consisting of a resistor and capacitor that set the charge time, when the capacitor is fully charged a threshold will be reached ad the transistor operating the relay will turn on,
The circuit will also monitor for high DC for each output if either were high then the circuit would not turn on the relay until the fault had been fixed.
The C315BEE version that has the surface mounted type protection board is not detailed in the service manual available in the public domain..
An authorised NAD service centre no doubt would have this version of the manual.
To answer your question when the main power from the power transformer is applied the protection circuit is also powered.
After approximately5 - 8 seconds the protection circuit will energise the speaker protection relay.
The time delay allows sufficient time for the large power supply capacitors to charge and eliminates the thud your hear in through the speakers.
The relay should not turn on immediately.
As this version of the protection circuit is using a combination of surface mount and conventional components, you should be able to check and confirm what is causing the issue.
The circuit normally has a charging circuit consisting of a resistor and capacitor that set the charge time, when the capacitor is fully charged a threshold will be reached ad the transistor operating the relay will turn on,
The circuit will also monitor for high DC for each output if either were high then the circuit would not turn on the relay until the fault had been fixed.
I remembered this thread from a while back and I even did a simulation of the discrete version of the protection module. Perhaps there is something useful here:
https://www.diyaudio.com/community/threads/relay-timing.348117/
https://www.diyaudio.com/community/threads/relay-timing.348117/post-6058554
https://www.diyaudio.com/community/threads/relay-timing.348117/
https://www.diyaudio.com/community/threads/relay-timing.348117/post-6058554
Those are generic transistors and can usually be substituted with BC546/BC556 types
2SC1015? do you mean 2SA which is a PNP.
The sim was OK as far as I recall although I think there was some problem with the relay drive and level shifting. This value works fine.
2SC1015? do you mean 2SA which is a PNP.
The sim was OK as far as I recall although I think there was some problem with the relay drive and level shifting. This value works fine.
Hi would i be possible to share the ASC file, When i tried to test the discrete design i found that multisim some be eratic, Also i am not sure how to Park Pin 1 since i did notunderst the ISC circuit. every version of the datasheet changes external component values here and there a bit.Those are generic transistors and can usually be substituted with BC546/BC556 types
2SC1015? do you mean 2SA which is a PNP.
The sim was OK as far as I recall although I think there was some problem with the relay drive and level shifting. This value works fine.
the datasheet that i have has relay drive transistor as 22k, I think that is the relay for protection and the other RL0xx are for switching Speaker A and B
@Mooly if i want to use a VOM1271 or similar device ( Photo Mos driver - Opto Coupler ) instead of Relay to make it SSR - than i should connect the PNP transistors Collector to the Anode and let the Cathode go to Ground. this question is in reference to use a module instead of the IC.
Am I correct or did i miss something
Am I correct or did i miss something
You must add a series resistor with the LED in the coupler and the value depends on the supply voltage. In your diagram you attached you show 12 volts as the supply and so you would need approx 1k to give a 10 milliamp LED current.
In my sim of the NAD circuit it runs on 34 volt and would need about 3k for the LED.
Pin 1 of the coupler (anode) goes to the most positive point so the collector of the PNP.
In my sim of the NAD circuit it runs on 34 volt and would need about 3k for the LED.
Pin 1 of the coupler (anode) goes to the most positive point so the collector of the PNP.