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Project: M³ home studio speaker amp (now finished!! pics at page 10) - Page 7

post #91 of 153
1/25/10 at 8:29pm
Quote:
Originally Posted by Jaypee View Post
Do you think it's safe to test the PSUs (meaning inital check) without heatsinking the MOSFET's?
Deep inside, I think you already know the answer to that question
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post #92 of 153
1/25/10 at 8:32pm
Thread Starter 
LOL.. you know it, just checking
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post #93 of 153
1/25/10 at 8:38pm


The single most important DIY lesson I have learned is patience. Never rush anything.
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post #94 of 153
1/27/10 at 7:41pm
Thread Starter 
Well, IT'S ALIVE!!
...or at least the PSU's are.. turned on the power and the led goes on (and I do mean ON, christ, that thing almost blinded me!! might haveto swich to a more subtle one...)

I started running voltage checks, and I was hoping for 36VDC, but instead the other board gives me 34,1VDC and the other 33,7VDC ...?

I'm using 30VAC 100VA transformers, the BZX55C12 for D5 and 4,99kohm resistor for R10 so what's wrong?

the only difference between the two boards is that other one doesn't have LED or R16, which shouldn't affect much..

hints anyone?
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post #95 of 153
1/27/10 at 7:48pm
Quote:
Originally Posted by Jaypee View Post
Well, IT'S ALIVE!!
...or at least the PSU's are..
Good to hear

Quote:
turned on the power and the led goes on (and I do mean ON, christ, that thing almost blinded me!! might haveto swich to a more subtle one...)
What size resistor do you have at R16? In my experience you shouldn't go lower than the default of 10k, and even higher is still probably OK.

Quote:
I'm using 30VAC 100VA transformers, the BZX55C12 for D5 and 4,99kohm resistor for R10 so what's wrong?
There can be reasonable variation between zeners, so don't fret the difference between boards. As for the lower voltage...... how sure are you that your multimeter is accurate?

Honestly, I wouldn't bother with the difference. My S11 is half a volt lower than it is 'supposed' to be.
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post #96 of 153
1/27/10 at 7:49pm
Measure the DC voltage across your D5 zener diode. Its voltage tolerance percentage translates directly into the output voltage error.
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post #97 of 153
1/27/10 at 7:58pm
Thread Starter 
Voltages across D5: 11,2V and 11,3V
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post #98 of 153
1/27/10 at 8:02pm
Quote:
Originally Posted by Jaypee View Post
Voltages across D5: 11,2V and 11,3V
11.2 * 3 = 33.6
11.3 * 3 = 33.9

Pretty damn close, so you just got low value zeners.
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post #99 of 153
1/27/10 at 8:03pm
11.2V is ~93.33% of 12V, so output is also ~93.33% of 36V at 33.6V.
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post #100 of 153
1/27/10 at 8:12pm
Thread Starter 
okay, so no biggie? phew..

I'll post pics as soon as I get the final wiring done. The amp is also almost done, and I might be able to fire it up tomorrow.

And I'll swich the value of R16 'til I find a suitable lighting.
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post #101 of 153
1/28/10 at 2:02am
Yep, it's no biggie. Low noise, good line and load regulation, low impedance, speed/bandwidth and other factors are important for an audio amp power supply, but absolute voltage accuracy isn't.
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post #102 of 153
1/28/10 at 6:18pm
Thread Starter 
Quick initial setup question:
does my setup (unbalanced inputs - balanced outputs without ground channel) affect my inital setup values? Cause I'm really alarmed right now..

tested for shorts - all clear. inserted opampr and put on power = no smoke or anything and the led goes on as planned.
start measuring - setting up the voltage over R5R to 0,45V with BIASOPR.
THEN:
Measured voltage between IG and OR and do I get under 100mV? No, ! get 10,2V ???
and measured across R9R I get 0,8mV?
need urgent help

EDIT: also pin 7 to IG and pin 4 to IG are cleared.
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post #103 of 153
1/28/10 at 6:28pm
Quote:
Originally Posted by Jaypee View Post
does my setup (unbalanced inputs - balanced outputs without ground channel) affect my inital setup values?
No.

Quote:
Measured voltage between IG and OR and do I get under 100mV? No, ! get 10,2V ???
and measured across R9R I get 0,8mV?
Make sure the correct MOSFETs are installed in all positions -- Q1+ should be IRFZ24N while Q1- should be IRF9Z34N.
Check solder joints.
Check virtual ground split.
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post #104 of 153
1/28/10 at 6:43pm
Thread Starter 
MOSFET's -Check
Solder joints - check (with eyesight)
How do I check virtual ground? The correct component is there if that's what you mean?

Installed OPAMPL and OR-IG is now about 4,5mV, but across R9R+ there's nothing..
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post #105 of 153
1/28/10 at 7:02pm
Quote:
Originally Posted by Jaypee View Post
How do I check virtual ground? The correct component is there if that's what you mean?
Last part of M³ Initial setup step 4.

Quote:
Installed OPAMPL and OR-IG is now about 4,5mV, but across R9R+ there's nothing..
It would be nothing until you turn the BIAS trimpot clockwise for a number of turns.
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