| dantwomey |
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 |
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| kilowattski |
| 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. |
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| Nelson Pass |
If both heat sinks heat up evenly, then you are 80% there.
What is the DC offset of the 2 channels? |
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| dantwomey |
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 |
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| Brian Donaldson |
| 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. |
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| eLarson |
| Check for the dreaded cold solder joint anywhere from the input jack to the input of the "bad channel," too. |
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| 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 |
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| Taco |
| 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. |
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| cowanrg |
| 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. |
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| eLarson |
| Might as well check all 5. |
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