MI Audio - Blues Pro  [traced]

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MI Audio - Blues Pro

Postby tonymcbony » 07 Jul 2015, 12:48

Hi folks, I was just building a blues pro up on vero and I have the weirdest issue.

All the knobs work (Gain does *something*, tone and vol work as they should) but it doesn't amplify the signal, but instead cuts out every second, like a slow tremolo. I changed out all the power caps just in case that was the problem but no dice.

I was using this http://tagboardeffects.blogspot.co.nz/2 ... s-pro.html layout.

Things I did differently; I did not include the fuzz or fat switch. I instead put a jumper between that trace that both switches connect to and the + of the 22uF cap going to ground. I also used a 51pf in place of the 30pf

Voltages on the IC are:

1 bounces around
2 0.07
3 0.01
4 0
5 0.65
6 0.09
7 bounces around
8 9.02

I've changed IC's no difference too. Something weird is happening though!
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Re: Blues Pro - weird pulsing and no gain?

Postby DrNomis » 08 Jul 2015, 08:16

tonymcbony wrote:Hi folks, I was just building a blues pro up on vero and I have the weirdest issue.

All the knobs work (Gain does *something*, tone and vol work as they should) but it doesn't amplify the signal, but instead cuts out every second, like a slow tremolo. I changed out all the power caps just in case that was the problem but no dice.

I was using this http://tagboardeffects.blogspot.co.nz/2 ... s-pro.html layout.

Things I did differently; I did not include the fuzz or fat switch. I instead put a jumper between that trace that both switches connect to and the + of the 22uF cap going to ground. I also used a 51pf in place of the 30pf

Voltages on the IC are:

1 bounces around
2 0.07
3 0.01
4 0
5 0.65
6 0.09
7 bounces around
8 9.02

I've changed IC's no difference too. Something weird is happening though!



That basically suggests to me that the circuit is motor-boating (oscillating) at a low frequency rather than amplifying, somehow the output-signal is being fed back into the input, have you tried turning the volume pot right down to zero and seeing if the voltage on pin 1 stops bouncing around?, if it does stop bouncing around then that suggests that the fault involves the volume pot.... :thumbsup


Have you made sure that all the copper track-cuts have been made in the correct places?, also, check to make sure that you haven't made any unintended short-circuits between the tracks while soldering the components.... :thumbsup


Hope that helps.... :thumbsup
Genius is not all about 99% perspiration, and 1% inspiration - sometimes the solution is staring you right in the face.-Frequencycentral.
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Re: Blues Pro - weird pulsing and no gain?

Postby tonymcbony » 09 Jul 2015, 01:12

Yep, that fixed the pulsing; I had 300k resistors instead of 330k.

Still doesn't actually raise the volume past unity for some reason.
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Re: Blues Pro - weird pulsing and no gain?

Postby DrNomis » 09 Jul 2015, 06:03

tonymcbony wrote:Yep, that fixed the pulsing; I had 300k resistors instead of 330k.

Still doesn't actually raise the volume past unity for some reason.




Hmmmm....a 300k resistor shouldn't have affected the operation of the circuit enough to cause the pulsing..... :hmmm:



Glad you fixed it though..... :thumbsup
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MI Audio Blues Pro  [traced]

Postby animalejo » 06 Mar 2018, 21:50

Hi !!

This is the MI Audio Blues Pro, i took the Tagboardeffects Rev 2, wich have the Fat Mode, and add to the premedit schematic:

MIAudioBluesProRev2layout.jpg
MIAudioBluesProRev2sch.jpg
MIAudioBluesProRev2pcb.jpg


Cheers ! :horsey:
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Re: MI Audio Blues Pro

Postby michael_ibrahim » 07 Mar 2018, 00:52

:roll:
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