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Old 2nd May 2006, 04:24 AM   #1
SteveA is offline SteveA  United States
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Default New Aleph 30

Well, I got my Aleph 30 "up and running". I used an Antek 800VA 39-0-39 wired for 230V as suggested by another member. With a CRC arrangement I end up with somewhat lower rail voltages (+/- 19.5V under load, down a bit from the 25V rails per design).

The DC offset measured very low <10 mV for both channels.

It plays music nicely but one channel gets hotter than its mate. The "hot" side has ~0.50-56 V drop across the source resistors (Vgs 4.00-4.10V for all FET's). The "cool" side has ~0.40 V drop and Vgs's at 3.96V for all three on one rail and two at 3.64V and one at 3.24V on the other).

I will replace the 3.24V FET with one to match the other two.

I'll check the source resistors to make sure they are all the correct value. Other than that is there any other reason for the discrepancy between the channels? Or should I be even be concerned?

SteveA
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Old 2nd May 2006, 04:46 AM   #2
Blues is offline Blues  United States
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Check value of R19 on both channels. Increasing R19 increases Vrsource. Also match Q5 if you can.
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Old 2nd May 2006, 06:03 AM   #3
SteveA is offline SteveA  United States
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Quote:
Originally posted by Blues
Check value of R19 on both channels. Increasing R19 increases Vrsource. Also match Q5 if you can.

Hi Blues,
R19 from the Pass schematic corresponds to R13 on BrianGT's boards (which I am using). Both channels have the correct 47.5k resistors in place (or at least the 47.5k found on the schematic).


Are you suggesting replacing both Q5's with matched units?
SteveA
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Old 2nd May 2006, 07:39 PM   #4
SteveA is offline SteveA  United States
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I had an FET or two come loose (screw was not tightened enuf). After tightening, I remeasured the amp and now see very consistent values (0.45-55V drops, Vgs's ~4V both rails, both sides). The heatsinks seem to be warming to temperature at the same rate.

Steve
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