C-Audio XR3801 Help

RobertG.be · 10th April 2009, 07:57 PM

Hello, I have a C-audio XR3801 amplifier that have problems.
I have 2 shematics for this amplifier, the first version of the schematic is without thermistance. The second have a reference to TH D370.

I found the shematic here : http://www.chaudio.co.uk/ServiceInfo/C-Audio/

The amplifier I have has no thermistance, I it has problem on a resistance : the R1 47R/23W becomes warm, and finally burns.
See XR3801 soft start sheet.

THe solution could be the use of these thermistances, but I can't find many informations about these. Can you help me about these D370 ???

Thanks a lot in advance for your help
Robert

ceharden · 10th April 2009, 09:58 PM

Hi there, glad my archive is useful! I only really ever set it up for my own use. It's only hosted from my house.

When the soft start resistor (R1) burns out, is the amp running normally at the time or does it have a fault?

If the amp powers up normally then the problem will be to do with the relay that is supposed to bypass the resistor once the amp has started up. If the amp doesn't power up then you have another fault which needs to be fixed first.

Replace the fuse in series with the resistor with a 60 or 100W lightbulb. This will limit the current and stop anything burning out immediately while you look for the main fault.

DubHertz · 9th May 2010, 07:42 PM

Hi I am looking for a service manual/schematic for the XR3801 but the link to your manuals require login details. Can you help?

AudioSystemsEng · 8th May 2011, 07:57 PM

Hi I wonder if either of you could send me a copy of the schematic. I'm used to working on RA-3000's so until i hear different, i'm going to assume its one of those with way too many output fets to be stable ;-D
thanks
jonathan

AudioSystemsEng · 8th May 2011, 08:04 PM

Scratch that... i've found a nice resource that really is free (at the moment).
Free Diagrams, Schematics and Service Manuals

It turns out the XR output design is slightly mad... 2 sets of supply rails, like a class g or h, then 2 sets of o/p devs, in series, with a floating driver for the high set. so its possibly a class h.
feel free to contradict me.. as long as it makes the thread useful to other visitors :-)

10th April 2009, 07:57 PM	#1
RobertG.be diyAudio Member Join Date: Apr 2009	C-Audio XR3801 Help Hello, I have a C-audio XR3801 amplifier that have problems. I have 2 shematics for this amplifier, the first version of the schematic is without thermistance. The second have a reference to TH D370. I found the shematic here : http://www.chaudio.co.uk/ServiceInfo/C-Audio/ The amplifier I have has no thermistance, I it has problem on a resistance : the R1 47R/23W becomes warm, and finally burns. See XR3801 soft start sheet. THe solution could be the use of these thermistances, but I can't find many informations about these. Can you help me about these D370 ??? Thanks a lot in advance for your help Robert

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10th April 2009, 09:58 PM	#2
ceharden diyAudio Member Join Date: Nov 2005 Location: Southampton	Hi there, glad my archive is useful! I only really ever set it up for my own use. It's only hosted from my house. When the soft start resistor (R1) burns out, is the amp running normally at the time or does it have a fault? If the amp powers up normally then the problem will be to do with the relay that is supposed to bypass the resistor once the amp has started up. If the amp doesn't power up then you have another fault which needs to be fixed first. Replace the fuse in series with the resistor with a 60 or 100W lightbulb. This will limit the current and stop anything burning out immediately while you look for the main fault.

9th May 2010, 07:42 PM	#3
DubHertz diyAudio Member Join Date: Mar 2010	Hi I am looking for a service manual/schematic for the XR3801 but the link to your manuals require login details. Can you help?

8th May 2011, 07:57 PM	#4
AudioSystemsEng diyAudio Member Join Date: Dec 2007	Hi I wonder if either of you could send me a copy of the schematic. I'm used to working on RA-3000's so until i hear different, i'm going to assume its one of those with way too many output fets to be stable ;-D thanks jonathan

8th May 2011, 08:04 PM	#5
AudioSystemsEng diyAudio Member Join Date: Dec 2007	Scratch that... i've found a nice resource that really is free (at the moment). Free Diagrams, Schematics and Service Manuals It turns out the XR output design is slightly mad... 2 sets of supply rails, like a class g or h, then 2 sets of o/p devs, in series, with a floating driver for the high set. so its possibly a class h. feel free to contradict me.. as long as it makes the thread useful to other visitors :-)

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