Mezmerize DCB1 Building Thread - Page 51

KatieandDad · 12:29 PM

Your heatsinks are all wrong.

At low current ie 10R (60mA) nothing will cook, but if you are HOTRODDING you will need to reorientate your heatsinks.

KatieandDad · 22nd April 2012, 12:41 PM

One other thing to check is that you haven't got any hairline shorts around the B1 buffer section.

OK my PCB was homebrew but I had minute shorts around the relay. That is why I decided to use the Salas Shunt Reg on its own with a regular B1 PCB.

Salas · 22nd April 2012, 01:17 PM

The Mosfets don't make full contact on the sinks in the picture! Dangerous.

Salas · 22nd April 2012, 01:22 PM

For the (L) offset the problem can be a dead JFET or wrongly matched by much in the right hand horizontal pair on the pic.

AndrewT · 02:04 PM

The output offset depends on what you feed into the DCB1 and on what the operating Id is, in comparison to the measured Idss of the amplifying jFET. It does not depend on the PSU voltages. It does not depend on the LED voltages. It does not depend on the CCS current.

Why have you braided your cable pairs/triplets for high inductance?
Twisting for low inductance, is much preferred for attenuating interference.

andreas w. · 22nd April 2012, 05:18 PM

Thank you for your answers and for your recommendations.

At first I will remove it out of the case (I didn´t expect problems ...) and will check and measure all the things you mentioned.

@Salas
I disconnected the heatsinks cause I thought it effects something.
I know they are oversized and will remove them.

Andreas

johnwmclean · 22nd April 2012, 07:55 PM

andreas, I don’t see any thermal grease applied, I would recommend to apply some.

andreas w. · 24th April 2012, 10:19 AM

Quote:

Originally Posted by Salas

For the (L) offset the problem can be a dead JFET or wrongly matched by much in the right hand horizontal pair on the pic.

I changed the JFET you mentioned.
Now I measure R -0,8 mV and L -1,7 mV DC offset.

It's better but good enough?

Andreas

Salas · 24th April 2012, 10:42 AM

Its very good. Are the supply voltages still alright? Check that you got 1.5-2VDC drop on the current set resistors too. Then you are good to play.

andreas w. · 25th April 2012, 06:40 PM

I measured 1.6VDC and it´s connected to Symasyms and sounds good at "Plastic Speakers" in the celler.
I have to finish the front plate and than it moves to my second setup which is DCB1, Symasym, Pearl (my first is ONO, Aleph P1.7, Aleph J :-).
I will post some pictures later.

Thank you very much for your help!

Andreas

22nd April 2012, 02:01 PM	#505
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	The output offset depends on what you feed into the DCB1 and on what the operating Id is, in comparison to the measured Idss of the amplifying jFET. It does not depend on the PSU voltages. It does not depend on the LED voltages. It does not depend on the CCS current. Why have you braided your cable pairs/triplets for high inductance? Twisting for low inductance, is much preferred for attenuating interference. Last edited by AndrewT; 22nd April 2012 at 02:04 PM.

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22nd April 2012, 12:41 PM	#502
KatieandDad diyAudio Member Join Date: Nov 2011 Location: UK	One other thing to check is that you haven't got any hairline shorts around the B1 buffer section. OK my PCB was homebrew but I had minute shorts around the relay. That is why I decided to use the Salas Shunt Reg on its own with a regular B1 PCB.

22nd April 2012, 01:17 PM	#503
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	The Mosfets don't make full contact on the sinks in the picture! Dangerous.

22nd April 2012, 01:22 PM	#504
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	For the (L) offset the problem can be a dead JFET or wrongly matched by much in the right hand horizontal pair on the pic.

22nd April 2012, 05:18 PM	#506
andreas w. diyAudio Member Join Date: May 2008 Location: NRW	Thank you for your answers and for your recommendations. At first I will remove it out of the case (I didn´t expect problems ...) and will check and measure all the things you mentioned. @Salas I disconnected the heatsinks cause I thought it effects something. I know they are oversized and will remove them. Andreas

22nd April 2012, 07:55 PM	#507
johnwmclean diyAudio Member Join Date: Oct 2009	andreas, I don’t see any thermal grease applied, I would recommend to apply some.

24th April 2012, 10:42 AM	#509
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Its very good. Are the supply voltages still alright? Check that you got 1.5-2VDC drop on the current set resistors too. Then you are good to play.

25th April 2012, 06:40 PM	#510
andreas w. diyAudio Member Join Date: May 2008 Location: NRW	I measured 1.6VDC and it´s connected to Symasyms and sounds good at "Plastic Speakers" in the celler. I have to finish the front plate and than it moves to my second setup which is DCB1, Symasym, Pearl (my first is ONO, Aleph P1.7, Aleph J :-). I will post some pictures later. Thank you very much for your help! Andreas