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Old 7th June 2012, 07:46 PM   #1
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Default ESP P27 PCB - Needs checking

Hi folks!

I have been working on the layout of Sir Rod Elliot's Guitar Amplifier.
I built the the power amp module but I am unable to set the quiescent current. On the minimum position of the 4k7 preset, I get the voltage at the collectors of the transistors at around 100mV!!
I also tried changing the pot twice...But it doesn't work....

Rod suggests us to set it at 11mV Which will set the quiescent current at a desirable 22mA.

Also when I run the amplifier, There is distortion and a lot of phasing too.
I don't understand what the problem is :/
It would be really thankful if someone could help me out with this problem
I have attached the layout that I have prepared for the amplifier.

Regards

Brutus
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File Type: jpg P27 Ver.1.JPG (867.8 KB, 446 views)

Last edited by brutus89; 7th June 2012 at 07:47 PM. Reason: forgot to mention something
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Old 8th June 2012, 05:58 AM   #2
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Anyone there???
I'm stuck!!
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Old 8th June 2012, 08:10 PM   #3
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Where does the power supply ground (0 V) connect to the circuit?

Where/how does the input signal ground connect to the amplifier ground?
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Old 9th June 2012, 05:33 AM   #4
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Quote:
Originally Posted by discrete View Post
Where does the power supply ground (0 V) connect to the circuit?

Where/how does the input signal ground connect to the amplifier ground?
It is done offboard, But I attached the layout with the connections now.

Thanks and Regards

Brutus
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File Type: jpg P27 Ver.2.JPG (869.5 KB, 295 views)
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Old 9th June 2012, 02:50 PM   #5
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Not sure if this is your problem, but the ground circuit is not ideal.
See the attachment. The highlighted track is the signal ground and has been modified to not share tracks with 1000 uF caps or the 10 ohm/100 nF zobel network.

How does the speaker return 0.1 ohm resistor connect?
It could be air-wired above or below the circuit board as shown in the attachment.
Can you show a complete diagram or photo, including the power supply?
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File Type: png P27 Ver.2 edit2.png (50.4 KB, 252 views)
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Old 9th June 2012, 04:11 PM   #6
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As well as the grounding issues Discrete has noticed, you include fuses yet some parts of the circuit (filter capacitors, input transistor connections) are connected before the fuses. I know this may simplify layout, but it also leaves these parts without the protection of the fuse if one of them was to go bang.
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Old 9th June 2012, 06:54 PM   #7
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Quote:
Originally Posted by discrete View Post
Not sure if this is your problem, but the ground circuit is not ideal.
See the attachment. The highlighted track is the signal ground and has been modified to not share tracks with 1000 uF caps or the 10 ohm/100 nF zobel network.

How does the speaker return 0.1 ohm resistor connect?
It could be air-wired above or below the circuit board as shown in the attachment.
Can you show a complete diagram or photo, including the power supply?
Quote:
Originally Posted by jackand08 View Post
As well as the grounding issues Discrete has noticed, you include fuses yet some parts of the circuit (filter capacitors, input transistor connections) are connected before the fuses. I know this may simplify layout, but it also leaves these parts without the protection of the fuse if one of them was to go bang.
Thanks a lot for your help!
I have modified the layout as per as your suggestions!

discrete : The 0.1E resistor is air-wired on the board!
jackand08 : I just feel so idiotic when you made me realize my mistake!!

Please check out the new layout!

Thanks and Regards!

Brutus!
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File Type: jpg P27 Ver.3.JPG (899.3 KB, 252 views)
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Old 10th June 2012, 09:43 PM   #8
alex mm is offline alex mm  Romania
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Default ESP 27 project PCB

...... @brutus89 just few hours of layout and PCB it's ready .
regards Alex .
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File Type: jpg PCB ESP27 BRUTUS.jpg (337.3 KB, 272 views)
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Old 11th June 2012, 03:06 PM   #9
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Absolutely Great work Mr. Alex!
Your PCBs are just amazing!!
Your PCBs always have that professionalism in them!!

I am able to see some modifications in the amplifier design...can you please explain me the change in the functions due to the modifications?
Thanks once again!

Awaiting your reply

Brutus!!
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Old 11th June 2012, 05:26 PM   #10
alex mm is offline alex mm  Romania
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Location: Baia Mare ,
...... I change, only thermal sensor, from BC 549 to BD 139 and aditional , optional power indicator LED for positive and negative rails . That's all , nothing special , folowed same schematic from ESP site Thanks for your kind words .
I'm glad, to help you, and others . BTW at home my wife call me also Brutus
That was the main reason for making this PCB .....
all the best Alex.
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