First Aleph troubleshooting help!

dantwomey · 4th December 2004, 06:44 PM

I'm about to ask some questions that have been asked many, many times in this forum so bear with me please. I've just completed my first DIY Aleph 5 and I have a problem. One channel works fine and the other channel produces nothing.

So far I've checked the following. Both LEDS light fine and the power supply produces the correct voltages for each channel. Both heatsinks seem to heat up evenly.

Would anyone like to get me started with some stuff to check? Any hints, tips, previous threads would be greatly appreciated.

Regards,
Dan

kilowattski · 4th December 2004, 07:15 PM

Start with the easy stuff. It seems as if the power supply is working because the LED is lit and you said you measured it coming into the bad channel. See you have half split the problem already. Is the input signal getting into the bad channel? If you have an oscilloscope check to see if the signal is getting into the bad channel. It seems that something may be working correctly because the bad channel is dissapating heat. Get the schematic from Passlabs.com and start noting some of the voltages on the bad channel on the schematic. Then start comparing the bad channel voltages with the good channel voltages. Pay particular attention to the voltages noted on the schematic from Passlabs. They are in the ballpark and your good channel voltages should be close to these. Once you come across a voltage that is wildly different chances you are in the problem area. Then check back and we can see if we can help narrow it down. This will help get you started.

Nelson Pass · 4th December 2004, 10:10 PM

If both heat sinks heat up evenly, then you are 80% there.

What is the DC offset of the 2 channels?

dantwomey · 5th December 2004, 12:17 AM

With an eight ohm resistor connected across the speaker terminals I get a DC offset of 38mV on the working channel and 44mV on the non-working channel after 60 seconds of power on.

Regards,
Dan

Brian Donaldson · 5th December 2004, 01:42 AM

If the heat sinks heat up evenly and you have less than 1v offset, I think you're 95% there. Look for a short in the input protection zeneers. If you have no offset, I'de guess the diff pair is working, but check voltage in current source resistor.

eLarson · 5th December 2004, 02:43 PM

Check for the dreaded cold solder joint anywhere from the input jack to the input of the "bad channel," too.

dantwomey · 5th December 2004, 05:08 PM

Haven't had time to do anything yet except make one more observation. Very faint 60hz hum coming from non-working channel with a signal.

Regards,
Dan

Taco · 6th December 2004, 08:01 AM

Quote:

Originally posted by dantwomey
Haven't had time to do anything yet except make one more observation. Very faint 60hz hum coming from non-working channel with a signal.

Regards,
Dan

As said before, you're almost there (I think) check your input cables. Also check on the XLR /RCA connector for shorts.

cowanrg · 6th December 2004, 07:55 PM

i had a problem similar to this with my aleph3's... it turned out to be a bad zener on the input. i would check all the zeners.

dantwomey · 6th December 2004, 08:08 PM

I'm using Kristijan's boards so I'm assuming D1 and D2 would be a good place to start or would I check all five Zeners?

http://web.vip.hr/pcb-design.vip/aleph-5.html

Regards,
Dan

4th December 2004, 06:44 PM	#1
dantwomey diyAudio Member Join Date: Feb 2002 Location: Canada	First Aleph troubleshooting help! I'm about to ask some questions that have been asked many, many times in this forum so bear with me please. I've just completed my first DIY Aleph 5 and I have a problem. One channel works fine and the other channel produces nothing. So far I've checked the following. Both LEDS light fine and the power supply produces the correct voltages for each channel. Both heatsinks seem to heat up evenly. Would anyone like to get me started with some stuff to check? Any hints, tips, previous threads would be greatly appreciated. Regards, Dan

4th December 2004, 07:15 PM	#2
kilowattski diyAudio Member Join Date: Aug 2003 Location: Long Island, New York	Start with the easy stuff. It seems as if the power supply is working because the LED is lit and you said you measured it coming into the bad channel. See you have half split the problem already. Is the input signal getting into the bad channel? If you have an oscilloscope check to see if the signal is getting into the bad channel. It seems that something may be working correctly because the bad channel is dissapating heat. Get the schematic from Passlabs.com and start noting some of the voltages on the bad channel on the schematic. Then start comparing the bad channel voltages with the good channel voltages. Pay particular attention to the voltages noted on the schematic from Passlabs. They are in the ballpark and your good channel voltages should be close to these. Once you come across a voltage that is wildly different chances you are in the problem area. Then check back and we can see if we can help narrow it down. This will help get you started. __________________ ----------------------------------------------- Kilowattski

5th December 2004, 02:43 PM	#6
eLarson diyAudio Member Join Date: Aug 2002 Location: Gaithersburg, MD	Check for the dreaded cold solder joint anywhere from the input jack to the input of the "bad channel," too. __________________ Would a woodchuck bother to chuck MDF?

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4th December 2004, 10:10 PM	#3
Nelson Pass The one and only Join Date: Mar 2001	If both heat sinks heat up evenly, then you are 80% there. What is the DC offset of the 2 channels?

5th December 2004, 12:17 AM	#4
dantwomey diyAudio Member Join Date: Feb 2002 Location: Canada	With an eight ohm resistor connected across the speaker terminals I get a DC offset of 38mV on the working channel and 44mV on the non-working channel after 60 seconds of power on. Regards, Dan

5th December 2004, 01:42 AM	#5
Brian Donaldson diyAudio Member Join Date: Jan 2003 Location: Texas, Love it or leave it	If the heat sinks heat up evenly and you have less than 1v offset, I think you're 95% there. Look for a short in the input protection zeneers. If you have no offset, I'de guess the diff pair is working, but check voltage in current source resistor.

5th December 2004, 05:08 PM	#7
dantwomey diyAudio Member Join Date: Feb 2002 Location: Canada	Haven't had time to do anything yet except make one more observation. Very faint 60hz hum coming from non-working channel with a signal. Regards, Dan

6th December 2004, 07:55 PM	#9
cowanrg diyAudio Member Join Date: Apr 2002 Location: Lafayette, CO	i had a problem similar to this with my aleph3's... it turned out to be a bad zener on the input. i would check all the zeners.

6th December 2004, 08:08 PM	#10
dantwomey diyAudio Member Join Date: Feb 2002 Location: Canada	I'm using Kristijan's boards so I'm assuming D1 and D2 would be a good place to start or would I check all five Zeners? http://web.vip.hr/pcb-design.vip/aleph-5.html Regards, Dan

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