Loud machine gun noise....

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jdubzamplification
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Loud machine gun noise....

Post by jdubzamplification »

Hello all! I haven't ever worked on this circuit, and here is what one is doing that was brought to be to fix... any idea what this is? Obviously it's the tremolo channel \ circuit, didn't know if anyone had encountered this before... Thanks!

https://youtu.be/A1GFn3OKzfs
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jdubzamplification
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Re: Loud machine gun noise....

Post by jdubzamplification »

NOTE: I already cleaned up the wiring a bit, most is neater and against the chassis now....still same issue.
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Bieworm
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Re: Loud machine gun noise....

Post by Bieworm »

Djeez... you've got Woody Woodpecker in there! :D
Provide us with the schematic and some detailed pics of your build.
Did you already try tube rolling?
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Daviedawg
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Re: Loud machine gun noise....

Post by Daviedawg »

This and related circuits can suffer from tremolo thump. But that seems extreme. Which version is it, i.e. do you have two channels one of which has tremolo? Does it change at all when you move knobs? Is it limited to one or both channels?
As asked already we need to know more about the circuit.

Dd
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jdubzamplification
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Re: Loud machine gun noise....

Post by jdubzamplification »

Bieworm wrote:
Mon 12/06/21 2:39 am
Djeez... you've got Woody Woodpecker in there! :D
Provide us with the schematic and some detailed pics of your build.
Did you already try tube rolling?
Yes. I have tried different tubes, actually new ones as well with same issue.
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jdubzamplification
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Re: Loud machine gun noise....

Post by jdubzamplification »

Here is what it appears to be, the Mojotone kit basically.

The WD matches what I am seeing. I will have to take pictures and post them, but everything appears to match the attached diagram \ schematic.
You do not have the required permissions to view the files attached to this post.
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jdubzamplification
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Re: Loud machine gun noise....

Post by jdubzamplification »

Daviedawg wrote:
Mon 12/06/21 3:14 am
This and related circuits can suffer from tremolo thump. But that seems extreme. Which version is it, i.e. do you have two channels one of which has tremolo? Does it change at all when you move knobs? Is it limited to one or both channels?
As asked already we need to know more about the circuit.

Dd
It does not change with volume\tone. It also appears that the trem channel does not respond to input.
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Bieworm
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Re: Loud machine gun noise....

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jdubzamplification wrote:
Mon 12/06/21 8:48 am
Here is what it appears to be, the Mojotone kit basically.

The WD matches what I am seeing. I will have to take pictures and post them, but everything appears to match the attached diagram \ schematic.
Aaaaahhh.. Mojotone docs!!! They are almost prone to get you in trouble! I really don't like the location of the footswitch jack. Like this the very sensitive wires have to cross/pass the entire output wiring. Mojotone completely ignores the rules of a good grounding scheme. Noisy trem is very often a layout or grounding problem. I wouldn't know where to begin honestly...first of all, very big mistake: the too long hot more to the footswitch jack lies parallel with the heater wiring... no no no!!!
Take a look in the Downloads section on this site and look for the modern classic 18W.. that's how it should be done in order to achieve a build that's bullit proof
Last edited by Bieworm on Mon 12/06/21 9:30 am, edited 1 time in total.
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jdubzamplification
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Re: Loud machine gun noise....

Post by jdubzamplification »

Bieworm wrote:
Mon 12/06/21 9:23 am
jdubzamplification wrote:
Mon 12/06/21 8:48 am
Here is what it appears to be, the Mojotone kit basically.

The WD matches what I am seeing. I will have to take pictures and post them, but everything appears to match the attached diagram \ schematic.
Aaaaahhh.. Mojotone docs!!! They are almost prone to get you in trouble! I really don't like the location of the footswitch jack. Like this the very sensitive wires have to cross/pass the entire output wiring. Mojotone completely ignores the rules of a good grounding scheme. Noisy trem is very often a layout or grounding problem. I wouldn't know where to begin honestly...
Take a look in the Downloads section on this site and look for the modern classic 18W.. that's how it should be done in order to achieve a build that's bullit proof
Yes, I am starting to realize that. I figured it was a grounding issue when I realized that the trem channel is dead to input. Also, I noticed the sweet layout in the layout section. Thank you!
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Re: Loud machine gun noise....

Post by JMPGuitars »

jdubzamplification wrote:
Mon 12/06/21 9:13 am
It does not change with volume\tone. It also appears that the trem channel does not respond to input.
In the video, the lead dress looks a mess. If you're seeing the mojotone layout, then the ground scheme is probably horrific. Look at the ground scheme thread in my signature, and try to get it to match that. I'd also make sure the amp is correct based on a SCHEMATIC.

With the amp off, highlighter verify the build with a SCHEMATIC. Start at the input and work your way through. Compare your schematic with one of the verified schematics from our Downloads section.

If there's a footswitch connection, try killing the tremolo with a footswitch. If not, with the amp off, you can carefully ground out the tremolo the same way a footswitch would (see schematics in Downloads section). Once the trem is canceled, see if you get any signal coming through that channel.

Thanks,
Josh
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Bieworm
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Re: Loud machine gun noise....

Post by Bieworm »

.first of all, very big mistake: the too long hot wire to the footswitch jack lies parallel with the heater wiring... no no no!!!
I would move that wiring to the ext speaker jack... and the ground wire should be at the preamp ground
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jdubzamplification
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Re: Loud machine gun noise....

Post by jdubzamplification »

JMPGuitars wrote:
Mon 12/06/21 9:29 am
jdubzamplification wrote:
Mon 12/06/21 9:13 am
It does not change with volume\tone. It also appears that the trem channel does not respond to input.
In the video, the lead dress looks a mess. If you're seeing the mojotone layout, then the ground scheme is probably horrific. Look at the ground scheme thread in my signature, and try to get it to match that. I'd also make sure the amp is correct based on a SCHEMATIC.

With the amp off, highlighter verify the build with a SCHEMATIC. Start at the input and work your way through. Compare your schematic with one of the verified schematics from our Downloads section.

If there's a footswitch connection, try killing the tremolo with a footswitch. If not, with the amp off, you can carefully ground out the tremolo the same way a footswitch would (see schematics in Downloads section). Once the trem is canceled, see if you get any signal coming through that channel.

Thanks,
Josh
Thanks man! I already addressed most of the wiring, dress issues after the video was taken. I will provide info one day this week once I can look at it again!
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jdubzamplification
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Re: Loud machine gun noise....

Post by jdubzamplification »

Bieworm wrote:
Mon 12/06/21 9:36 am
.first of all, very big mistake: the too long hot wire to the footswitch jack lies parallel with the heater wiring... no no no!!!
I would move that wiring to the ext speaker jack... and the ground wire should be at the preamp ground
Ok, will make that change and let you know.
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jdubzamplification
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Re: Loud machine gun noise....

Post by jdubzamplification »

Ok, here is an update. I changed the grounding scheme to match the WD in the downloads section and removed the footswitch jack (for now).

Before, the TREM channel was dead, but now is responsive to input.

The problem still exists, but is now affected by the volume, tone, etc.

This is the strangest thing I have ever encountered....

Any help is appreciated.
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Re: Loud machine gun noise....

Post by Bieworm »

jdubzamplification wrote:
Sat 12/18/21 4:56 pm
Ok, here is an update. I changed the grounding scheme to match the WD in the downloads section and removed the footswitch jack (for now).

Before, the TREM channel was dead, but now is responsive to input.

The problem still exists, but is now affected by the volume, tone, etc.

This is the strangest thing I have ever encountered....

Any help is appreciated.
Maybe you can post new pics of the amp after the changes you've made?
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