Quad 405-2 limiter circuit - Page 4

vzs · 1st June 2006, 09:30 AM

Hello Tibi!

Did you managed to do the modification of the current source into QUAD 405 class A stage?

If yes, could you share the schematics with us.

Thanks,
Zsolt

Thomo · 17th May 2007, 10:37 AM

Hi everyone. I know this is an old thread but I have modded my Quad 405 and think I have a problem and I would very much appreciate any help given.

It does make music, but I am unsure of the quality as I daren't connect to decent speakers.

I have done the dc daylight mods, but now I think R31 is overheating. It gets very hot, very quickly and smells like it's going to give up! It is like this on both channels.

Please help, anyone.

Regards, Lee.

dcd · 17th May 2007, 11:07 AM

Lee

R31 and R30 are in series and so should have exactly the same current flowing through them - they should both get hot as they are dissipating about 1.1W - my mods do not affect this area of the circuit.

If R31 is significantly hotter than R30 then you have a problem with C10 which is passing d.c. - is it connected correctly ?? please tell me you did NOT fit a bipolar cap for C10.

Regards

Keith

DCD

Thomo · 17th May 2007, 11:24 AM

Quote:

Originally posted by dcd

If R31 is significantly hotter than R30 then you have a problem with C10 which is passing d.c. - is it connected correctly ?? please tell me you did NOT fit a bipolar cap for C10.

Regards

Keith

DCD

Thanks for the reply.

Nope, no bipolar. It is a correctly fitted 100uF 100v Panasonic FC.

Should I also have upgraded tr1? Your M12368 to mod-3 schem shows 2sa1085 but this is not mentioned in your upgrade text.

I read correct voltages on both sides of r31 but insure of current.

Regards, Lee.

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1st June 2006, 09:30 AM	#31
vzs diyAudio Member Join Date: Dec 2005 Location: Cluj-Napoca, Romania	Hello Tibi! Did you managed to do the modification of the current source into QUAD 405 class A stage? If yes, could you share the schematics with us. Thanks, Zsolt

17th May 2007, 10:37 AM	#32
Thomo diyAudio Member Join Date: Nov 2006	Hi everyone. I know this is an old thread but I have modded my Quad 405 and think I have a problem and I would very much appreciate any help given. It does make music, but I am unsure of the quality as I daren't connect to decent speakers. I have done the dc daylight mods, but now I think R31 is overheating. It gets very hot, very quickly and smells like it's going to give up! It is like this on both channels. Please help, anyone. Regards, Lee.

17th May 2007, 11:07 AM	#33
dcd diyAudio Member Join Date: Jan 2006	Lee R31 and R30 are in series and so should have exactly the same current flowing through them - they should both get hot as they are dissipating about 1.1W - my mods do not affect this area of the circuit. If R31 is significantly hotter than R30 then you have a problem with C10 which is passing d.c. - is it connected correctly ?? please tell me you did NOT fit a bipolar cap for C10. Regards Keith DCD

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