audio1st said:
I am using the same rectifier to test each side. I will use separate rectifiers when both + & - supplies are running simultaneously
Yes I swapped the resistors over
I'm just going to remeasure the v+ side
-V
'A' -28.2v
'B' -34.1v
'C' -35.3v
Output -26.2v
+V
'A' +27.5v
'B' +28.7v
'C' +28.7v
Output +25.6v
If I take a reading from the drain pin I get +35.2V
Do you know why the connection to J309 is different to the negative side?
'A' -28.2v
'B' -34.1v
'C' -35.3v
Output -26.2v
+V
'A' +27.5v
'B' +28.7v
'C' +28.7v
Output +25.6v
If I take a reading from the drain pin I get +35.2V
Do you know why the connection to J309 is different to the negative side?
Hi Richard,
The point of the readings was to find the voltage across each component.
V-
A is V across zener (28.2)
Difference between A, B is V across J-Fet (5.9)
Difference between B, C is V across 130r, (1.2)
V+
A is V across zener (27.5)
Difference between A, B is V across 130r, (1.2)
Difference between B, and total V, is V across J-Fet, ( 6.5)
Current across 130r is (ohms law), 1.2/130 =9.2mA.
I should avoid the maths, I'm bound to get pulled up on it
Barry.
The point of the readings was to find the voltage across each component.
V-
A is V across zener (28.2)
Difference between A, B is V across J-Fet (5.9)
Difference between B, C is V across 130r, (1.2)
V+
A is V across zener (27.5)
Difference between A, B is V across 130r, (1.2)
Difference between B, and total V, is V across J-Fet, ( 6.5)
Current across 130r is (ohms law), 1.2/130 =9.2mA.
I should avoid the maths, I'm bound to get pulled up on it
Barry.
there's nothing wrong with your arithmetic.
One can measure the voltage drops direct across the components. It might be slightly easier on the striped side. Or add some soldered test points to clip on to.
One can measure the voltage drops direct across the components. It might be slightly easier on the striped side. Or add some soldered test points to clip on to.
Hi
I have finally built the second power supply and have also change the zener on the -V of the first.
Would you mind casting your eyes across these figures?
Thanks
Richard
First Power Supply with -V Zener replaced
-V
'A' -28v
'B' -33.4v
'C' -34.5v
Output -25.8v
Voltage across JFet -5.4v
Voltage across 130R -1.1v
Current across 130R 8.5mA
+V
'A' +27.6v
'B' +28.6v
'C' +28.6v
Output +25.5v
Voltage across 130R +1v
Voltage across JFet +3.1v
Current across 130R 7.7mA
Second Power Supply
-V
'A' -27.8v
'B' -33.8v
'C' -34.8v
Output -25.6v
Voltage across JFet -6v
Voltage across 130R -1v
Current across 130R 7.7mA
+V
'A' +27.8v
'B' +29.1v
'C' +29.1v
Output +25.9v
Voltage across 130R +1.3v
Voltage across JFet +3.2v
Current across 130R 10mA
I have finally built the second power supply and have also change the zener on the -V of the first.
Would you mind casting your eyes across these figures?
Thanks
Richard
First Power Supply with -V Zener replaced
-V
'A' -28v
'B' -33.4v
'C' -34.5v
Output -25.8v
Voltage across JFet -5.4v
Voltage across 130R -1.1v
Current across 130R 8.5mA
+V
'A' +27.6v
'B' +28.6v
'C' +28.6v
Output +25.5v
Voltage across 130R +1v
Voltage across JFet +3.1v
Current across 130R 7.7mA
Second Power Supply
-V
'A' -27.8v
'B' -33.8v
'C' -34.8v
Output -25.6v
Voltage across JFet -6v
Voltage across 130R -1v
Current across 130R 7.7mA
+V
'A' +27.8v
'B' +29.1v
'C' +29.1v
Output +25.9v
Voltage across 130R +1.3v
Voltage across JFet +3.2v
Current across 130R 10mA
why do you show the B & C voltages the same on the +ve supply and yet you calculate the voltage drop as 1.0V or 1.3V?
AndrewT said:
Thanks for pointing out my mistake!
First Power Supply with -V Zener replaced
-V
'A' -28v
'B' -33.4v
'C' -34.5v
Output -25.8v
Voltage across JFet -5.4v
Voltage across 130R -1.1v
Current across 130R 8.5mA
+V
'A' +27.6v
'B' +28.6v
+34.5v (Total voltage taken from drain pin of J309)
Output +25.5v
Voltage across 130R +1.0v
Voltage across JFet +5.9v
Current across 130R 7.7mA
Second Power Supply
-V
'A' -27.8v
'B' -33.8v
'C' -34.8v
Output -25.6v
Voltage across JFet -6v
Voltage across 130R -1v
Current across 130R 7.7mA
+V
'A' +27.7v
'B' +29.0v
+34.3v (Total voltage taken from drain pin of J309)
Output +25.9v
Voltage across 130R +1.3v
Voltage across JFet +5.3v
Current across 130R 10mA
So, if I read this correctly, to drive my 8 ohm speakers my LM3886 amps will be fed with plus and minus 28 to 35 vdc for a total of 56 to 70 volts dc?
Hi Richard,
Your results all seem fine, as long as the output voltage is close to being equal for all rails, you have correctly made the circuits..😉
I have been trying to get a closer match of rail voltages without critical zener matching.
So I added a trimmer to each side and can now match voltages, I tested it on LTspice and found no abnormal readings.
Your results all seem fine, as long as the output voltage is close to being equal for all rails, you have correctly made the circuits..😉
I have been trying to get a closer match of rail voltages without critical zener matching.
So I added a trimmer to each side and can now match voltages, I tested it on LTspice and found no abnormal readings.
Attachments
audio1st said:Hi Richard,
Your results all seem fine, as long as the output voltage is close to being equal for all rails, you have correctly made the circuits..😉
I have been trying to get a closer match of rail voltages without critical zener matching.
So I added a trimmer to each side and can now match voltages, I tested it on LTspice and found no abnormal readings.
Hi Barry
Thanks for letting me know 🙂
What value trimmer did you use on your board?
Richard
Hi Richard,
I haven't said were I put it yet😉
I will have to show on diagram later, I can't explain it easily. It is probably a no-no anyway.
Barry.
I haven't said were I put it yet😉
I will have to show on diagram later, I can't explain it easily. It is probably a no-no anyway.
Barry.
When you two are quite ready, there is the small matter of how you like the sound with the regulated supply! If you wait much longer you will need to replace those lytics! 😀
I must remember my manners....thanks for all of your help so far!
I'll probably be back sooner than you think😉
I'll probably be back sooner than you think😉
was this Q ever answered?Redshift187 said:
Start with the lowest power of bulb.
If it goes off after the initial flash then all is probably OK. Check some voltages to confirm correct operation.
If it glows slightly, check the voltage entering the transformer. If this is >95% of mains voltage AND the circuit voltages are all OK, then operate the bypass switch without going to a higher wattage bulb.
If the low wattage bulb is causing a significant voltage drop on the mains side AND the checked voltages are OK, then change to a higher rated bulb and recheck operating voltages. If OK then operate bypass switch.
The only need for higher wattage bulbs is to suit amps that dissipate a higher quiescent power.
An amp that is biased to 10mA from +- 28Vdc is only half a watt + transformer loss.
An amp that is biased to 200mA from +-50Vdc is 20W + transformer loss. A different load that will requires a different bulb. Start low to be safe, it does no harm.
The one exception is to a soft start resistor. This must not stay in circuit if the input voltage is too low. It will overheat if a low voltage is fed to the primary.