Powered up: no scratchy volume pot!
DC on the outer pins: fluctuating between 2,5 and 3,2 mV tendency slowly rising, but I'll have to measure that again in half an hour or so to confirm it's actually rising.
It looks we're on the right track to get this board to behave like it should!
Regards Jan.
DC on the outer pins: fluctuating between 2,5 and 3,2 mV tendency slowly rising, but I'll have to measure that again in half an hour or so to confirm it's actually rising.
It looks we're on the right track to get this board to behave like it should!
Regards Jan.
Hi Chris,
The only error I can find/measure is that pin 1 of the right hand IC and pin 7 of the left hand IC are not connected.
DC update: fluctuating between 1,9 and 2,9mV.
Regards, Jan.
Hi Jan,
No, the pin 1 of the right hand IC and pin 7 of the left hand IC are not connected on the PCB layout and schematic.
Bypassing the two 3.3µF capacitors suggested by @MarcelvdG does the trick!👍
You can remove the capacitor on the volume pot as it is not needed anymore.
No, the pin 1 of the right hand IC and pin 7 of the left hand IC are not connected on the PCB layout and schematic.
Bypassing the two 3.3µF capacitors suggested by @MarcelvdG does the trick!👍
You can remove the capacitor on the volume pot as it is not needed anymore.
Just being curious: does it work now without any capacitor on the volume potmeter, so with the TL072 and the two shorted 3.3 uF capacitors as the only modifications?
Hi Marcel,
The board is now working with just the two 3,3uF NP capacitors bridged.
I left the NE5532P in place; I did swap it for a TL072 on a previous occasion, which had no effect on the scratcing pot, so the NE5532P was put back, see post #5: https://www.diyaudio.com/community/threads/scratchy-pot-on-tenghong-low-pass-filter.401145/
The board that is operational, is the one I added the two 10K resistors to (no effect); these have been removed, together with the two 3,3uF near the volume pot
The board I removed the volume pot from and added the capacitor to the wiper doesn't work (at all), after I put the pot back in it's place. I'll have to check if I damaged something to cause this, I had to use a large soldering iron to have sufficient heat to get the leadfree solder off, this may have been too much...
If I don't get this board to work, it's no big deal; I have a replacement underway with a 50% discount from the seller.
Regards, Jan.
The board is now working with just the two 3,3uF NP capacitors bridged.
I left the NE5532P in place; I did swap it for a TL072 on a previous occasion, which had no effect on the scratcing pot, so the NE5532P was put back, see post #5: https://www.diyaudio.com/community/threads/scratchy-pot-on-tenghong-low-pass-filter.401145/
The board that is operational, is the one I added the two 10K resistors to (no effect); these have been removed, together with the two 3,3uF near the volume pot
The board I removed the volume pot from and added the capacitor to the wiper doesn't work (at all), after I put the pot back in it's place. I'll have to check if I damaged something to cause this, I had to use a large soldering iron to have sufficient heat to get the leadfree solder off, this may have been too much...
If I don't get this board to work, it's no big deal; I have a replacement underway with a 50% discount from the seller.
Regards, Jan.
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