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.
kubeek said: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.
What do u mean by +parts?
Do you mean measureing the gate on the fets? And in that case how should i measure? What should i look for.
I just tested the opamps.. they get +/- 15V on the correct legs.
Im a beginner so bare with me
Thank you
ok the drainvoltages arekubeek said:by the +parts I meanrt the legs of the transistors which are connected to the +voltage, check the voltage by multimeter.
8,4V on T1
5,89v on T2
15,25V on T3
but i dont know if this is what its suppose to be..
Any ideas
Thanks
about this signalcheck.. Could I plug in a mp3 player, and then use a pair of headphones, grounding the common and one of the speakers and using the tip on the headphonejack to probe on my pcb? That way just listen how "far" the signal gets in the path.
Or how would you do it?
Thanks
Or how would you do it?
Thanks
XXLPeanut said:about this signalcheck.. Could I plug in a mp3 player, and then use a pair of headphones, grounding the common and one of the speakers and using the tip on the headphonejack to probe on my pcb? That way just listen how "far" the signal gets in the path.
Or how would you do it?
Thanks
I did this and I could only get a signal until i hit the first resistor... after this I coudnt find any signal anywhere.
Any ideas?
anatech said:Hi XXLPeanut,
Are you sure your jacks are wired with the resistor between them and the summing point? Are the resistors the correct value?
-Chris
Yes they are the correct value..
Here you can see the first half of my pcb
edit: I cant attach a picture or can I just not see it.. hmm
anatech said:Hi XXLPeanut,
Problems in the engine room. Please stand by, do not adjust your set .....
They will be fixed.
-Chris
lol.. like your humour chris hahaha.. let me know when I can upload
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..
Mp3 is ok, but I think headphones don´t have high enough impedance. You should use something with amplification to check the signal - like mike input on computer´s sound card + headphones or speakers set to listen to the mike.
Oh and a great thing would be oscilloscope, if you have.
Oh and a great thing would be oscilloscope, if you have.
kubeek said:Mp3 is ok, but I think headphones don´t have high enough impedance. You should use something with amplification to check the signal - like mike input on computer´s sound card + headphones or speakers set to listen to the mike.
Oh and a great thing would be oscilloscope, if you have.
Ill take another look in an hour or so.. I have a pair of beyer dt990 2x600 ohm headphones.
And yeah.. a scope would be sweet... Read: have none hehe.
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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