kmj,
I would love to help, but I don't have enough information. I would have to know what kind of trafo you are using and how you have it connected, what your PS circuit looks like, etc....
Pictures would help a lot.
Cheers!
Russ
I would love to help, but I don't have enough information. I would have to know what kind of trafo you are using and how you have it connected, what your PS circuit looks like, etc....
Pictures would help a lot.
Cheers!
Russ
trafo is 2x12V and 2,25VA per secondary winding.
capacitors are 150uF-150uF-100nF before the regulator and 100nF-220uF after.
I tested the supply with a 4,7K and later a 1K load and it worked fine, then I connected it to the preamp and one of the regulators stopped working.
they are (+ - )12V and rated to 1,5A
capacitors are 150uF-150uF-100nF before the regulator and 100nF-220uF after.
I tested the supply with a 4,7K and later a 1K load and it worked fine, then I connected it to the preamp and one of the regulators stopped working.
they are (+ - )12V and rated to 1,5A
Attachments
Maybe, if you draw some current, the secondary voltage of the transformator drops too far, so that it becomes lower than the sum of output voltage and dropout voltage.
Mick
Edit: I just see that you have a 12V trafo. That should be fine....
Mick
Edit: I just see that you have a 12V trafo. That should be fine....
Well, I had at bigger transformer earlier. 17,5V and 85mA per winding.
I went over to the local supermarket just now and bought a 9V battery. The Preamp works, thats for sure. I did however blow a pair of speakers earlier trying it with the powersupply. Cheap pieces of crap but the were useful when testing amps.
I went over to the local supermarket just now and bought a 9V battery. The Preamp works, thats for sure. I did however blow a pair of speakers earlier trying it with the powersupply. Cheap pieces of crap but the were useful when testing amps.
Hi again, I built a powersupply using the datasheet for the 7812-regulators and etched a new pair of Mono-yardbird PCBs. I have 47pF on the cap designated CRF and on the RG I have 0,85R since I didn't have the exact value.
My casing is made of MDF with aluminumfoil on the inside connected to ground. Internat wire is unshielded.
The problem is a buzz combined with a sparking sound that is more or less constant. What should I look after to solve this?
My casing is made of MDF with aluminumfoil on the inside connected to ground. Internat wire is unshielded.
The problem is a buzz combined with a sparking sound that is more or less constant. What should I look after to solve this?
An update and some changes. I added 470uF between each fuse and the first capacitor.
So on the positive rail it's fuse->470uF->0,33uF->reg->0,1uF
and on the negative it's Fuse->470uF->2,2uF->reg->1,0uF
The positive, negative and common rail ends with a dual pinhead which connects to the two boards.
So the powerstarground is at the PSU-board and the signalground is as specified on the board. The signalground of each channel is separated from the common with a 0,82ohm resistor.
When the CD is connected to the poweramp directly there's no buzzing sound so it should be the pre that is the source.
Attaching a schematic of the PSU (one psu to two channels)
So on the positive rail it's fuse->470uF->0,33uF->reg->0,1uF
and on the negative it's Fuse->470uF->2,2uF->reg->1,0uF
The positive, negative and common rail ends with a dual pinhead which connects to the two boards.
So the powerstarground is at the PSU-board and the signalground is as specified on the board. The signalground of each channel is separated from the common with a 0,82ohm resistor.
When the CD is connected to the poweramp directly there's no buzzing sound so it should be the pre that is the source.
Attaching a schematic of the PSU (one psu to two channels)
Attachments
No, Swedish apartmentbuildings doesn't have i mainsground in the wall-socket. It is stated in some law that when renovating a threepronged socket containing mainsearth must be installed but that is when and if thers a renovation. So no.
And I can't seem to think of a way to seperate the ground of the two channels.
Oh, one more thing. If I disconnect the ampboards from the PSU and drive one channel only with a 9V battery, when there's still buzzing.
And I can't seem to think of a way to seperate the ground of the two channels.
Oh, one more thing. If I disconnect the ampboards from the PSU and drive one channel only with a 9V battery, when there's still buzzing.
kmj said:
You could not power it from a single 9Volt.
You would need two, connect in series, with the mid point (where you connect the two) being your ground.
Cheers!
Russ
Ok, I just tested but Batterypower is not an option i'm sorry to say. It's for a friend not fond of the idéa.
kmj said:
And did it work?
If it did then the problem is with the PS.
Do you have a dual scondary trafo?
If so I would use two bridges.
Oh, you missunderstood me. I just tested with the one battery. I only have one but I could buy another tomorrow. And I have more bridges to add if it might help. And the trafo has dual secondaries
The key thing will be to test that you have a good clean +12 to GND and -12V to GND from the respective outputs of the the PS.
I would test the preamp itself with two batteries first though, just to be sure there is not a problem there.
I would test the preamp itself with two batteries first though, just to be sure there is not a problem there.
Not if you turn the paper upside-down when putting it in the UV-box
I managed to etch it on the wrong side and that's why the OPs are on the copperside, they are however correct. Forgot to mention it 🙂
I went for a run to the nearest gasstation and I'm now in possesion of two 9V batteries. Stay tuned!
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