Chassis Shielding
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- jpmucka
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Chassis Shielding
All,
I am in the process of fitting my 18 Watt Chassis (GDS Amps) to a Mojo 18 Watt 1x12 Cabinet. The Mojo cabinet comes without the braces that allow you to suspend the chassis from the cabinet internally so I have made some braces myself and I fitting the braces using the chassis as a guide.
My question is twofold. First, has anyone applied shielding material, e.g. thin aluminum, to the upper back panel of the cabinet. My thought is that this is done on 50 and 100 Watt heads so there must be a reason. Second, if you have a cabinet with internal braces to suspend the chassis, did you secure the upper back panel with screws into the chassis. The only reason I could see doing this is to prevent vibration, which is probably reason enough!
Thanks in advance for any help!
Jim Mucka
I am in the process of fitting my 18 Watt Chassis (GDS Amps) to a Mojo 18 Watt 1x12 Cabinet. The Mojo cabinet comes without the braces that allow you to suspend the chassis from the cabinet internally so I have made some braces myself and I fitting the braces using the chassis as a guide.
My question is twofold. First, has anyone applied shielding material, e.g. thin aluminum, to the upper back panel of the cabinet. My thought is that this is done on 50 and 100 Watt heads so there must be a reason. Second, if you have a cabinet with internal braces to suspend the chassis, did you secure the upper back panel with screws into the chassis. The only reason I could see doing this is to prevent vibration, which is probably reason enough!
Thanks in advance for any help!
Jim Mucka
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Jim
I think the extra shield on the backplate for the chassis is a good idea. It will keep out stray interrference and this is why you see it on some amps. If you go with the shield you will need some way so make an electrical connection between the chassis and the aluminum plate. This is done by securing the upper backpanel to the chassis with screws. It will also make for a more sturdy mounting of your chassis.
Nothing worse than starting out a song with "Breaker Breaker 19.........."
Dana
I think the extra shield on the backplate for the chassis is a good idea. It will keep out stray interrference and this is why you see it on some amps. If you go with the shield you will need some way so make an electrical connection between the chassis and the aluminum plate. This is done by securing the upper backpanel to the chassis with screws. It will also make for a more sturdy mounting of your chassis.
Nothing worse than starting out a song with "Breaker Breaker 19.........."
Dana
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HVAC Tape over the inside of the back panel does the trick and it is cheap and easy. As long as the back panel is in contact with the chassis, you'll be ok. There are other methods that are equally good, but more expensive and a little more challenging to implement (brass screen or plate, aluminum screen or plate, etc.).
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- bob-i
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I kinda like getting AM radio on my 18watt....
ya it gives you something to play along with. Unfortunatly the only thing on AM these days seems to be talk radio and I just cant picture Rush Limbaugh singing along with the band.
Like Dartanion said, you should check your cable and I would also look at your lead dress (keep wires as short as posible) Look for cold solder connections inside the amp chassis. Sometimes a bad connection will act like a diode. If you are picking up radio without the cable plugged in you may have a input jack that isn't grounding properly. Sometimes these can be a b@#ch to track down.
ya it gives you something to play along with. Unfortunatly the only thing on AM these days seems to be talk radio and I just cant picture Rush Limbaugh singing along with the band.
Like Dartanion said, you should check your cable and I would also look at your lead dress (keep wires as short as posible) Look for cold solder connections inside the amp chassis. Sometimes a bad connection will act like a diode. If you are picking up radio without the cable plugged in you may have a input jack that isn't grounding properly. Sometimes these can be a b@#ch to track down.
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If you get interference it can be hard to determine where it comes from - I used to have a Gibson SG that picked up Radio Moscow if you cranked everything up!
My contribution to this thread is to tell you how to solder to the aluminium tape so it can be grounded properly.
Aluminium forms an oxide coat on its surface which defies soldering. Furthermore, some of that aluminium tape has a plastic coat on top of the aluminium layer, which makes soldering even harder. On the other hand, connection is vague unless solder is used - you can connect mechanically in the first instance, but the connection will oxidise with age.
To get round this you need a craft knife, some flux, a 25W iron and some solder. Pick the location you want to join on the tape - don't go too close to the edge or end, as the adhesive will be no good under the area you solder. Put a blob of flux on it. Scratch the surface beneath the flux with the tip of the craft knife blade - the flux will stop the air getting to the area, and the oxide layer is scratched off. If the tape is plastic coated, you have to be careful - you can scratch through the plastic and expose the aly just the same, but the aly layer tends to be thinner (and therefore penetrable). Get a good loading of solder of the tip of the iron, and try to solder a blob on the scratched area - it does work as long as the area is thoroughly scratched to remove the oxide. Do not try to join the earthing wire at the same time until you have practised this technique a few times. With practise you can screen and earth anything using nothing more sophisticated than duct tape! You can solder to an aluminium chassis the same way, but you do need a big iron.
My contribution to this thread is to tell you how to solder to the aluminium tape so it can be grounded properly.
Aluminium forms an oxide coat on its surface which defies soldering. Furthermore, some of that aluminium tape has a plastic coat on top of the aluminium layer, which makes soldering even harder. On the other hand, connection is vague unless solder is used - you can connect mechanically in the first instance, but the connection will oxidise with age.
To get round this you need a craft knife, some flux, a 25W iron and some solder. Pick the location you want to join on the tape - don't go too close to the edge or end, as the adhesive will be no good under the area you solder. Put a blob of flux on it. Scratch the surface beneath the flux with the tip of the craft knife blade - the flux will stop the air getting to the area, and the oxide layer is scratched off. If the tape is plastic coated, you have to be careful - you can scratch through the plastic and expose the aly just the same, but the aly layer tends to be thinner (and therefore penetrable). Get a good loading of solder of the tip of the iron, and try to solder a blob on the scratched area - it does work as long as the area is thoroughly scratched to remove the oxide. Do not try to join the earthing wire at the same time until you have practised this technique a few times. With practise you can screen and earth anything using nothing more sophisticated than duct tape! You can solder to an aluminium chassis the same way, but you do need a big iron.
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