DIY progress report

Pass X2.2

Hello and good day, this is my first post in the forum.
I have purchased a X2.2 recently. The preamplifier should be complete according to the seller. When I received the goods missing on 2 of the modules respectively 2SK389BL and 2SK109BL. As a substitute I matched 2SK170BL and 2SJ74BL used. Can anyone give a guide how to measure and adjust the bias current on the modules?
Many thanks in advance
 
Hello diy community! I was not quite sure where to write, so let it be this topic now :) I got my hands on couple of pcb:s that claim to be Aleph 5 clone, little bit of google and those are probably kk-pcb Aleph 5 - clone boards. So, im building my first amplifier (monoblock pair) based on these. Now i wish i had chosen a bit easier project at first!

I have two 2 x 30v 545VA toroids, CRC and 176 000uF capacitance, so far only part that is ready is psu..and my question is about that. I tried to measure psu voltage after capacitors, without dummy load, or load at all. Results confuse me, voltage raised to 38v or so, then it start slowly to climb down. Is this normal, is it possible to measure whole psu without load?

Sorry my english..

Thanks!
 
pictures please

Here is couple before soldering. What is missing from pictures are 25w 0.1ohm resistors where wires are cut in the middle. 2,2kohm 5w bleeder resistors and 4,7uf capacitors for filtering also added before test.

But pictures wont solve my questions, how voltage should act when powering psu up without any load? Stable from the beginning? I kept those powered up only a short while. First start was of course with light bulb current limiter without problems. Did not dare to keep power on for longer while, got worried about voltage readings :)
 

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The Mains Bulb Tester will protect your transformer from damage if you have a wiring fault. For this early stage of wiring/testing use a 25W, or 40W bulb.

Have you measured the input and output at the transformer without any PSU connected?
Post results.

Then add the bridge rectifier. Post results.
Then add one pair of smoothing caps. Post results.
 
The Mains Bulb Tester will protect your transformer from damage if you have a wiring fault. For this early stage of wiring/testing use a 25W, or 40W bulb.

Have you measured the input and output at the transformer without any PSU connected?
Post results.

Then add the bridge rectifier. Post results.
Then add one pair of smoothing caps. Post results.

Should i measure with bulb tester, or without it, does it matter? With bulb tester everything seems ok, i used 40w and 75w bulbs. I have fired it up already with normal power cord also.

I havent measured part by part yet, i will do it and post results when ready :) thanks for helping me out!
 
you are trying to find out why the voltage starts to drop.
So go back to the start and test in stages.

You need input AND output voltages so that you can check that the transformer is giving an expected output.
And you can leave the Tester in circuit because the current draw is near zero (the leakage through the smoothing caps when you attach them).
 
you are trying to find out why the voltage starts to drop.
So go back to the start and test in stages.

You need input AND output voltages so that you can check that the transformer is giving an expected output.
And you can leave the Tester in circuit because the current draw is near zero (the leakage through the smoothing caps when you attach them).

Ok, now were getting somewhere. I must have some kind of problem with my measurings earlier or my old & cheap multimeter; i made several measurements now and there was no decreasing voltage!

Input from wall: 230v
Output from transformer: 2 x 31v
After bridge rectifier: 28.4v, both same
Rails: +/-42.4v

Final stupid question, but i have to be sure..measuring rail voltages:
Multimeter black wire to ground, red wire to positive lead (42.4v). Black stays grounded, red wire to negative lead (-42.4v).

Multimeter red to positive lead, black to negative lead (84.8v).

Sorry for these newbie questions, as i said; this in my first amplifier project and it feels kinda hard time to time, so much learning and nothing with my language. Next one will likely to be much easier!

Oh, btw! I heard that these PCB:s are not "authorized" by mr. Pass, is this correct? It's definetly not too late to change plans if so, and make another Pass amplifier if there is any version that accept my existing psu?
 
.................
Input from wall: 230v
Output from transformer: 2 x 31v
After bridge rectifier: 28.4v, both same
Rails: +/-42.4v
this looks good.
...........measuring rail voltages:
Multimeter black wire to ground, red wire to positive lead (42.4v). Black stays grounded, red wire to negative lead (-42.4v).

Multimeter red to positive lead, black to negative lead (84.8v).
This confirms your measurements are good.

You measured 230:31Vac.
this is the unloaded voltage from the secondary. You probably have a 28Vac transformer. That's the voltage when the all the secondaries are delivering their rated currents, simultaneously.
............... I heard that these PCB:s are not "authorized" by mr. Pass, is this correct? It's definetly not too late to change plans if so, and make another Pass amplifier if there is any version that accept my existing psu?
Did you buy them from N.Pass?
If so then they are "authorised".

If you bought fakes/clones from a crook selling someone else's IP, then you can't expect any support from N.Pass.
 
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this looks good.This confirms your measurements are good.

You measured 230:31Vac.

Did you buy them from N.Pass?
If so then they are "authorised".

If you bought fakes/clones from a crook selling someone else's IP, then you can't expect any support from N.Pass.

Great, thank you!

I got these PCB's second handed. Hmm, i have to study a little where and what i could get to replace these. I guess rail voltage is kinda high for most Pass desings.
 
Most Pass designs are ClassA.
Expect the transformer VA to be between 6times and 10times the maximum ClassA output.
i.e. a 50W+50W ClassA stereo amplifier would need a minimum of a 600VA transformer and may perform better with a 1000VA transformer of the correct voltage.

I know, that's why i have these huge heatsinks also :) one pair of 545VA toroids, so monoblock build it is..
 
545VA allows from 55W of ClassA to 90W of ClassA
42Vdc will drop down to ~+-38Vdc when biased to ClassA
That would give you >>90W into 4ohms
or around 70W to 80W into 8ohms.
Your transformer is fixing your output into an 8ohms speaker with a maximum ClassA of around 75W
Output bias would be >2.1A and dissipation will be ~160W

This is well beyond a standard F5.
Have a good read of the F5 and F5t to see if these are what you want.
I don't know tha Aleph range.
 
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