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PostPosted: Tue Sep 06, 2022 10:48 pm 
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Hello everyone,
i hope someone can assist me with this issue. When i turn the Mid knob beyond about 50% the Crown Jewel starts oscillating and gets progressively worse from that point on. Can someone point me in the right direction as to what is wrong. Everything appears to be correct regarding component placement and solder joints.

Thank You


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PostPosted: Wed Sep 07, 2022 11:33 am 
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Please provide pics.

1. What make/model power supply are you using?
2. If you remove the charge pump and switch to 9v mode, does the problem persist?

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PostPosted: Thu Sep 08, 2022 12:09 am 
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Hi, thank you for your reply.

I have tested this with an analog power supply, switching ps and a 9v battery. No change with either power source.

I tested the pedal with and without the 18v ic with no change in the issue.

I have attached a display dump of my small scope as well as pictures of the pcb. Please note the peripherals and pots were removed to examine and photograph the pcb.


Attachments:
PCB_2.jpg
PCB_2.jpg [ 792.78 KiB | Viewed 580 times ]
PCB_1.jpg
PCB_1.jpg [ 367.35 KiB | Viewed 580 times ]
1.jpg
1.jpg [ 72.86 KiB | Viewed 580 times ]
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PostPosted: Thu Sep 08, 2022 10:52 am 
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You didn't need to remove the pots and jacks. Did you put them back yet? Does the problem persist?

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PostPosted: Sun Sep 25, 2022 11:24 pm 
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Hi,
i have done quite a lot of testing. The same issue is still present.
I am starting to think it may be a fault on the PCB itself.

Regards
Peter Gooch


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PostPosted: Mon Sep 26, 2022 10:49 am 
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Couple of things:

  • How do the MID FREQ pot and the MID Q toggle switch affect the oscillation behavior?
  • It appears that two eyelets for capacitor C10 may be solder-bridged, but that's difficult to judge conclusively from the photo of the back of the PCB (see mark-up below). Not sure if this could be a factor in your problem, but it should be checked and fixed if I'm correct.

Attachment:
CJ_C10_solder.jpg
CJ_C10_solder.jpg [ 31.49 KiB | Viewed 405 times ]

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PostPosted: Tue Sep 27, 2022 7:12 pm 
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Thank You for the reply.
Unfortunately the issue remains. I am going to try retouching all the solder joints(again) to see if there is a bad joint somewhere.
Changing the switch and adjusting the Mid dial does change the tone of the oscillation.

Regards
Peter Gooch


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PostPosted: Wed Sep 28, 2022 12:35 pm 
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Please do not start removing components unless instructed to. That is the worst thing you can do.

Reflowing your solder joints is a good idea. If that doesn't help, please take voltage readings of all the ICs.

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Please do not PM me. email is prefered. keith@buildyourownclone.com


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PostPosted: Wed Sep 28, 2022 5:01 pm 
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Hi,
thank you for your reply. I have reflowed the board with no change. I have also replaced the TL072 with no change.
The related caps and resistors appear to be within tolerance.

Regards
Peter Gooch


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PostPosted: Thu Sep 29, 2022 6:52 am 
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Can you please post voltage readings for each of the ICs? If you've never used your meter to check voltages, let us know and we can provide more guidance.

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PostPosted: Fri Sep 30, 2022 6:20 am 
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Thank you for the voltage hint.
The voltages to the two opamps were as expected. However the pic microcontroller voltage was incorrect. Turns out IC3 and Q3 were in the wrong places.

Pedal works as expected now.
Thank You for you help.


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PostPosted: Fri Sep 30, 2022 9:57 am 
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Glad to hear that you found & fixed the problem. Enjoy!

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My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2


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