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Old 15th March 2014, 10:08 PM   #21
infinia is offline infinia  United States
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Quote:
Originally Posted by Trileru View Post
Red is top side and is ground, and bottom is blue and is power plane and stops at the regulator. I don't know how to show the bottom side as all the information is already in that picture Later on, after I replace the oil in my bike and give it a nice wash I will add some more capacitance on the output of the board and make the tests. I have a couple of 8ohm 100W resistors.
take a snap shots of the actual board and I can compare to the earlier image to see if the ground plane overlaps. I used to use MOSFETs and a function generator to make dynamic PS tests with dummy loads too.
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Old 16th March 2014, 02:32 AM   #22
Trileru is offline Trileru  Romania
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I have done some more tests with various output capacitor configurations.
Basically there is no change. I used 50hz as test frequency for the input signal into the amp. I should have chosen something else but anyway I made a test with 16ohm resistance load and I saw no ripple whatsoever.
So this is with 2x10uF tantalum output capacitance (the way I'm using it right now):
Click the image to open in full size.

This is with one 330uF/25V Panasonic FC:
Click the image to open in full size.

This is with 1500uF/25V Samwha RD (standard capacitor, not low-esr):
Click the image to open in full size.

This is with the same 1500uF Samwha capacitor but I added another Samwha SD series (same, standard capacitor, normal ESR) 4700uF/50V half way between the PS board and TDA amp:
Click the image to open in full size.

This is with 16ohm resistor (two 8ohm in seris) added directly on the output of the PS board. I want to mention that with 8ohm the board did not output the full voltage/current. With 16ohm I got 16.5V at 1A.

Click the image to open in full size.

Also I'd like to mention that this is what the oscilloscope shows when I have the PS turned off, so it's some noise picked by the whole circuit from the surroundings. So between on/off there's no change.
My oscilloscope was set on AC coupling, 10x probe and I had my DMM measuring the current.

This is what the PCB looks like:

Top side:

Click the image to open in full size.

Bottom side:

Click the image to open in full size.
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Old 16th March 2014, 02:38 AM   #23
Trileru is offline Trileru  Romania
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Quote:
Originally Posted by sextaafondo View Post
Hi, as I stated earler in the thread I think you will benefit from extra capacitance (large value) on the output side if you install a high current and gain device like a darlington transistor. That way you will unload the regulator transfering the job to the pass device. It will also take care of the large capacitance charging current and keep the voltage value steady.
At the moment I would prefer to "fix" this board if that's possible. Adding other components outside the board + heatsink etc would be too much effort. I'd prefer to make the board all over again.
Also, since I'm using this amp at about 0.05 - 0.1W usually, I don't see why I'd change anything. I'm just curious about this effect that I'm seeing, I would like to learn about it and know what I did wrong. And maybe fix it. But I wouldn't make the whole pcb again, not worth it.
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Old 16th March 2014, 02:47 AM   #24
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Where are you connectiong your probes? At the load or PSU output?
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Old 16th March 2014, 03:10 AM   #25
Trileru is offline Trileru  Romania
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Quote:
Originally Posted by funk1980 View Post
Where are you connectiong your probes? At the load or PSU output?
At the PSU output. As I've said before, ground is on C5 negative leg and signal from C6 positive leg.
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Old 16th March 2014, 10:40 AM   #26
infinia is offline infinia  United States
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Hi
so your static load test shows you are losing regulation somewhere between 1 and 2 amps. > seems low for an audio power amp driving two 8 ohm speakers?
IMO you should be able to support at least 6-4 ohm (short term) static load and still have good regulation if you want full volume from the power amp for stereo 8 ohm speakers. otherwise you will be seeing ripple and noise at peaks. IDK lower the output voltage some?


PS I can recommend some AC enhancements to the power supply later , but you'll probably have solve the ambient noise pickup 1st.
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Last edited by infinia; 16th March 2014 at 11:09 AM.
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Old 16th March 2014, 11:22 AM   #27
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[QUOTE=Trileru;3856885]this is with 16ohm resistor (two 8ohm in seris) added directly on the output of the PS board. 8ohm the board did not output the full voltage/current.I want to mention that with With 16ohm I got 16.5V at 1A.



What is the spec of the transformer you are using
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Old 16th March 2014, 11:25 AM   #28
infinia is offline infinia  United States
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my back of the of hand the calculations 15+15 W output at 50% eff = 60W total dynamic power from the power supply so @ at 16.5 = 3.6 A of short term power ie don't expect continuous sine waves ( lab conditions )
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Old 16th March 2014, 11:27 AM   #29
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[QUOTE=Trileru;3856885]this is with 16ohm resistor (two 8ohm in seris) added directly on the output of the PS board. I want to mention that with 8ohm the board did not output the full voltage/current. With 16ohm I got 16.5V at 1A.




What is the spec. of the transformer you are using .


Apologies for the double post . I did try to fully edit post 27 but ended up with 2 posts .

Last edited by epicyclic; 16th March 2014 at 11:33 AM.
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Old 16th March 2014, 12:21 PM   #30
Trileru is offline Trileru  Romania
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My transformer is a toroidal 16VAC/80VA.
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