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Aleph J illustrated build guide
Aleph J illustrated build guide
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Old 28th June 2020, 09:33 PM   #5241
6L6 is offline 6L6  United States
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Aleph J illustrated build guide
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Old 29th June 2020, 04:11 AM   #5242
freejazz00 is offline freejazz00  United States
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Thanks Iíll keep it in mind.

I completed both the continuity test on the transformer (no issues) and floating the transformer ground (no help). Iíll call Antek tomorrow.

If anyone can think of another test I should run in the meantime please let me know. Thanks
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Old 29th June 2020, 04:33 AM   #5243
Extreme_Boky is offline Extreme_Boky
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NOTE: this is a long shot... do it if you are keen on experimenting and you have time.

Connect the secondary windings to the power supply PCB, load the power supply PCB with amp PCB's, and then use a series combination of 0.1uF /50V AC film capacitor and a 20-ohm potentiometer (you'll need two sets of these), across each secondary winding. While the amp is ON (transformer fully loaded with both amp PCB's), rotate the potentiometers to see if the buzz changes... If you have an oscilloscope, monitor the AC windings for oscillations and see if you have any, and if you do, if the potentiometer rotation is affecting oscillations' amplitude.
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Old 29th June 2020, 04:59 AM   #5244
freejazz00 is offline freejazz00  United States
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I don’t have an oscilloscope. I can try it otherwise. Can you send me a wiring diagram?
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Old 29th June 2020, 05:28 AM   #5245
Extreme_Boky is offline Extreme_Boky
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Old 30th June 2020, 11:07 PM   #5246
kengler13 is offline kengler13  United States
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Default Bias issue

I finished assembly of my Aleph J, and am having an issue with the left channel bias. Right channel I was able to adjust offset and bias with no issue. however in the left channel, I can adjust offset to 0, but I cannot get the bias to go past .274 V. I have turned R27 to it's maximum and it will go no further.
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Old 1st July 2020, 05:15 AM   #5247
freejazz00 is offline freejazz00  United States
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I spoke with Antek today. They want me to measure the temp of the transformer and rectifiers. They asked me to swap out rectifiers, if possible. I may have one extra one, but I’m not likely to have two. I also imagine that it is more likely that the transformer is problematic than the rectifiers. They also want me to swap out this transformer for the one I have in my M2x. I said no to the last point since Im not going to break anything that works well to test another that doesn’t. That’s not good engineering practice as I may end up with two amps with problems. I’ll go for the measurements and rectifiers and report back. Thanks
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Old 1st July 2020, 07:43 AM   #5248
eddyvb is offline eddyvb  Belgium
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Best to isolate the problem. Take the transfo out, and put some load on the secondaries with resistors. Say if you have wired the diode bridge wrong, and a diode shorts half the cycle of the AC. Maybe you make the same error again when replacing the diodes or bridge. And you then make the wrong conclusion that the transfo is faulty.
(About temperature of the transfo, when connecting only the power supply without the amp's, the transfo must stay at about room temp.)
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Old 1st July 2020, 01:40 PM   #5249
freejazz00 is offline freejazz00  United States
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How do I put a load on the secondaries with resistors with the transformer out? Thanks
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Old 1st July 2020, 04:48 PM   #5250
Ben Mah is offline Ben Mah  Canada
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Aleph J illustrated build guide
To calculate load resistors use Ohm's Law. It works with AC voltage when the load is resistive (V = I x R).

The power rating of the resistors will need to be quite large though.

First to determine the load. You pointed out earlier that the transformer hummed with one channel connected. Each channel has two mosfets up and two mosfets down with the following current demand:

.40V across .47R for each mosfet

I=V/R= .40v/.47R = 0.85A per mosfet = 2 x 0.85A = 1.70A per V+ and V- per channel

Transformer secondary = 18VAC

Resistive load = V/I = 18VAC/1.70A = 10.6R

So the resistive load across each 18VAC secondary is 10.6R to approximate the load of one channel. Round up to standard resistor value.

Power requirement of the resistors P = IxIxR = 1.70A x 1.70A x 11R = 31.8W

As I mentioned at the beginning, the power handling requirement is quite high. You can series and parallel a bunch of 10W resistors to get say 60W at 11R. The resistors will get hot!

You will need a resistor load for each 18VAC secondary.

Or, swap out the rectifiers and also check temperature as suggested by Antek.

The 11R resistor loads are for one half amplifier load or one channel of the amplifier. You can perhaps try loading the transformer less (higher R value) to see if it hums if you do not have enough high wattage resistors.
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