Hello.
I just finished this preamp.
http://www.albertkreuzer.com/preamp.htm
And now for the big question.. It wont play.
The problem is not in the psu. That delivers +/- 15V as expected.
Should I take off all potmeters and switches and put them on one by one or how would you errortest it?
When I've had power on it and I turn it off, the threshold LED turns on for ½ sec as the caps are discharging I suppose.
When I put in a pair of headphones and turn up the gain I hear a click-like sound when the meter is about 2/3 turned up.. P1 and P7 are both in middle position. As well are all meters.
Any ideas or could the problem be anywhere?
Thanks
I just finished this preamp.
http://www.albertkreuzer.com/preamp.htm
And now for the big question.. It wont play.
The problem is not in the psu. That delivers +/- 15V as expected.
Should I take off all potmeters and switches and put them on one by one or how would you errortest it?
When I've had power on it and I turn it off, the threshold LED turns on for ½ sec as the caps are discharging I suppose.
When I put in a pair of headphones and turn up the gain I hear a click-like sound when the meter is about 2/3 turned up.. P1 and P7 are both in middle position. As well are all meters.
Any ideas or could the problem be anywhere?
Thanks
First check the voltage on all + parts of the transistors, and the both supplies of the op-amp.
If it doesn´t help, then I would suggest making a signal-probe. As it is a bass preamp, you could take a tape player and connect it to the input. Then connect a jack-jack wire to some combo, make the shield grounded to your circuit, and start touching the signal part of the ciruit with the tip of the jack, and listen where the signal ends.
If it doesn´t help, then I would suggest making a signal-probe. As it is a bass preamp, you could take a tape player and connect it to the input. Then connect a jack-jack wire to some combo, make the shield grounded to your circuit, and start touching the signal part of the ciruit with the tip of the jack, and listen where the signal ends.
First I got an arrormessage that it was too big.. then i reduced the size and the message was posted
Here ill try again.
If you want you can send me a mail on nlindhardt@hotmail.com or put it on msn and ill send you the pcb
If its any help the resistance between my grounplane and ground on the psu is around 1 ohm.. all supplys are ok and DGS voltages on the fets seem to be ok..
Here ill try again.
If you want you can send me a mail on nlindhardt@hotmail.com or put it on msn and ill send you the pcb
If its any help the resistance between my grounplane and ground on the psu is around 1 ohm.. all supplys are ok and DGS voltages on the fets seem to be ok..
600ohms is not enough, even thoug it is far better than 16 or 32.
Check the signal, and also have a look at cold joints and check if the transistors are connected right - D goes to D, G to G and S to S
Then the Q2 and Q3 gate voltages seem a bit suspicious. Try if G2 changes with changing the P2, and the G3 should be 3.5V, and not 2V, but this could be due to high values of R23 and R24.
Check the signal, and also have a look at cold joints and check if the transistors are connected right - D goes to D, G to G and S to S
Then the Q2 and Q3 gate voltages seem a bit suspicious. Try if G2 changes with changing the P2, and the G3 should be 3.5V, and not 2V, but this could be due to high values of R23 and R24.
kubeek said:600ohms is not enough, even thoug it is far better than 16 or 32.
Check the signal, and also have a look at cold joints and check if the transistors are connected right - D goes to D, G to G and S to S
Then the Q2 and Q3 gate voltages seem a bit suspicious. Try if G2 changes with changing the P2, and the G3 should be 3.5V, and not 2V, but this could be due to high values of R23 and R24.
Hehe.. all t's are connected right. G2 changes between 0 when turned up and and 5.2 V when turned down when i change P2 and I still get 1,99V on G3.
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