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Old 18th March 2017, 10:09 AM   #2331
AndrewT is offline AndrewT  Scotland
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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).
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Old 18th March 2017, 02:37 PM   #2332
Juntuin is offline Juntuin  Finland
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Quote:
Originally Posted by AndrewT View Post
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?
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Old 18th March 2017, 03:03 PM   #2333
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by Juntuin View Post
.................
Input from wall: 230v
Output from transformer: 2 x 31v
After bridge rectifier: 28.4v, both same
Rails: +/-42.4v
this looks good.
Quote:
...........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.
Quote:
............... 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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Last edited by AndrewT; 18th March 2017 at 03:05 PM.
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Old 18th March 2017, 03:17 PM   #2334
Juntuin is offline Juntuin  Finland
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Quote:
Originally Posted by AndrewT View Post
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.
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Old 18th March 2017, 03:37 PM   #2335
AndrewT is offline AndrewT  Scotland
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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.
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Old 18th March 2017, 03:43 PM   #2336
Juntuin is offline Juntuin  Finland
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Quote:
Originally Posted by AndrewT View Post
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..
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Old 19th March 2017, 09:49 AM   #2337
AndrewT is offline AndrewT  Scotland
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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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Last edited by AndrewT; 19th March 2017 at 09:56 AM.
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