I recently bought a new power amp board for my old Gallien Krueger 700rbII - it had been broken for a while.
When i connected it everything was good but it has since developed a loud ground hum every time I turn it on. The noise sometimes disappeared when i moved the amp or tapped it in a certain place so I looked inside and the problem seemed to be something mechanical related to the speaker output jacks, I looked and saw tiny pieces of metal poking out of the front of them. thinking i had found the problem, i filed them down, but now the amp just makes the sound all the time and I can't get rid of it.
I now think that the problem was the main board needs a ground and those tiny pins were the only way it was grounded to the chassis. But here's the thing im confused about - I can't see any way that the main board should be grounded - the IEC inlet is grounded to the chassis, but nothing on the secondary side of the transformer is. Were those *tiny* pins really the *only* ground for the power amp board?
maybe someone can tell me if this is normal to have only the IEC inlet ground and the power board not connected to ground? Or should the power amp board definitely be grounded?
any help much appreciated 🙂
When i connected it everything was good but it has since developed a loud ground hum every time I turn it on. The noise sometimes disappeared when i moved the amp or tapped it in a certain place so I looked inside and the problem seemed to be something mechanical related to the speaker output jacks, I looked and saw tiny pieces of metal poking out of the front of them. thinking i had found the problem, i filed them down, but now the amp just makes the sound all the time and I can't get rid of it.
I now think that the problem was the main board needs a ground and those tiny pins were the only way it was grounded to the chassis. But here's the thing im confused about - I can't see any way that the main board should be grounded - the IEC inlet is grounded to the chassis, but nothing on the secondary side of the transformer is. Were those *tiny* pins really the *only* ground for the power amp board?
maybe someone can tell me if this is normal to have only the IEC inlet ground and the power board not connected to ground? Or should the power amp board definitely be grounded?
any help much appreciated 🙂
The amplifier has a single point ground and yes those metal spikes were the ground.
Order new connectors, fit them and ensure the fixings are hand tight.
Order new connectors, fit them and ensure the fixings are hand tight.
ah... not the answer I was hoping for but thankyou!
I contacted the distributor to ask for a part number, do you know what the correct term for those pins on the front is? I'll try and find them on mouser etc. too
I contacted the distributor to ask for a part number, do you know what the correct term for those pins on the front is? I'll try and find them on mouser etc. too
You could use a large tag washer to fit around the stem of the socket, making good contact with the chassis and solder the tag to the point that the tags were connected to, forming a ground bond between the chassis and the ground point on the pcb behind the socket.
Have you got a socket on the old board you could use?
Have you got a socket on the old board you could use?