Page 1 of 9
Noise section trimmer voltage?
Posted: Jan 15th, '14, 20:44
by effegee
I don't know if it is significant, but I cannot get 130mV on pin 1 of the 4558 when adjusting the trimmer in the noise section. The closest I can get is 120mV.
Re: Noise section trimmer voltage?
Posted: Jan 18th, '14, 00:45
by Patrick
I got arround 250mV AC but have to check on monday with a better DMM with 6 digits 0.01% Tolerance.
Most cheap dmm have in AC measurement a high Tolerance.
Re: Noise section trimmer voltage?
Posted: Jan 18th, '14, 08:03
by e-licktronic
Dear,
Try to change R127 Value by 4.7Kohm.
Best regards,
e-licktronic
Re: Noise section trimmer voltage?
Posted: Jan 19th, '14, 16:28
by effegee
e-licktronic wrote:Try to change R127 Value by 4.7Kohm.
Changing it to 18K seems to work. I guess the proof will be when it's all put together and I can do some audio tests.
Re: Noise section trimmer voltage?
Posted: Jan 21st, '14, 14:30
by e-licktronic
Changing it to 18K seems to work. I guess the proof will be when it's all put together and I can do some audio tests.
Glad to ear you say
Best regards,
e-licktronic
Re: Noise section trimmer voltage?
Posted: Jan 21st, '14, 22:55
by 4teenth
Hmm... The closest I could get it is 180mV...
Have I gone wrong somewhere?
Re: Noise section trimmer voltage?
Posted: Jan 21st, '14, 23:16
by 4teenth
Yes, i appears so : Wrong value caps in C16, 18, and 20
Re: Noise section trimmer voltage?
Posted: Jan 21st, '14, 23:50
by 4teenth
Okay.... corrected my error but still can only get down to 160mV..
Re: Noise section trimmer voltage?
Posted: Jan 22nd, '14, 00:36
by 4teenth
Okay, just went through everything, tested all values of resistors and checked values of cpacitors. All good. So still confused as to why I'm getting a different minimum mV value....
Re: Noise section trimmer voltage?
Posted: Jan 22nd, '14, 03:46
by klingklang
I too am having issues with trimming to the correct voltage on pin 1 of U24, the lowest I can get is about 250mV.
All components have been checked and rechecked and they appear to be correct.
However while checking for errors, I noticed that the resistor pictured for R127 does not match the one listed in the build guide. The image is of a 47K resistor as opposed to the listed 4K7 and due to my excessive voltage problem I'm wondering which value is correct? I currently have a 4K7 in R127.
Edit: I've just noticed that the original 808 schematic lists a 4K7 for R127, so that's likely the correct value (and the image must be mismatched). I'll have to look for the source of the problem elsewhere.