buschfsu
Well-known member
anyone?
fet boy
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maxheadroom
Well-known member
what is the current consumption?
skipwave
Well-known member
[quote author="buschfsu"]ok, im a bit tired but i have it hooked up and im using scotts voltage regulator so i get 23.94V dc to the board. problem is i get 23.94v everywhere. all of the bias points, R5, before C2, can this be right? i don't have another meter here to check, but it appears to be working ok with a 1.5v battery. won't pass signal through DI either
any suggestions?[/quote]
If you don't have the fet installed, don't worry about 24 volts at C2. You are feeding 24V to the fet drain resistor, and without the fet attached to draw some current there won't be a voltage drop across the drain resistor, so the 24V will show up on the low side of it, where it connects to the base of the output darlington pair.
On the other hand, if R5, 100 ohms, actually has 24V across it, the dissipation will be several watts and it will die a quick death.
Check grounding. Is the board ground connected to the same 0V reference as the power supply?
any suggestions?[/quote]
If you don't have the fet installed, don't worry about 24 volts at C2. You are feeding 24V to the fet drain resistor, and without the fet attached to draw some current there won't be a voltage drop across the drain resistor, so the 24V will show up on the low side of it, where it connects to the base of the output darlington pair.
On the other hand, if R5, 100 ohms, actually has 24V across it, the dissipation will be several watts and it will die a quick death.
Check grounding. Is the board ground connected to the same 0V reference as the power supply?
imloggedin
Well-known member
can someone point me to where i can buy a fetboy PCB?? i cant seem to find anywhere to buy it. ive been searching through threads, maybe i just missed something.
thanks
thanks
buschfsu
Well-known member
yes that was it, connected fets biased to 12v and everything is happy. thick gooey fet goodness!!
www.braudio.com gil may have some fetboys. he distributes them in the us.
www.braudio.com gil may have some fetboys. he distributes them in the us.
fucanay
Well-known member
Ok, after messing with these things for a real long time, I finally finished putting them together. But I have massive hum with anything plugged in or not and when I turn the pot up it squeals like a pig. This is on both channels.
I'm convinced it's a grounding issue. But I don't know how. Could some one tell me how this is supposed to be grounded? Like from where to where?
Or do you have any other suggestions of what to try?
Matt
I'm convinced it's a grounding issue. But I don't know how. Could some one tell me how this is supposed to be grounded? Like from where to where?
Or do you have any other suggestions of what to try?
Matt
maxheadroom
Well-known member
hi matt,
have you got a photo?
i got also problems with my fetboy, but in my case it is oszillating.
how did you connect the TS-Jack?
have you got a photo?
i got also problems with my fetboy, but in my case it is oszillating.
how did you connect the TS-Jack?
fucanay
Well-known member
No Photo yet, but I tried just about everything I could think of, including some things that blew the fuse. I just haven't really seen detailed pictures of the inside of anyone else's fetboys. I'd love to see some.
And call me crazy, but is the pin 1 on the PCB for input and output connected to nothing at all, other than the pad itself?
Matt
And call me crazy, but is the pin 1 on the PCB for input and output connected to nothing at all, other than the pad itself?
Matt
lofi
Well-known member
[quote author="fucanay"]
And call me crazy, but is the pin 1 on the PCB for input and output connected to nothing at all, other than the pad itself?
Matt[/quote]
:?:
my son was 18 yesterday so i have my thick head on this morning, but do you mean the wire from pin 1 on the mic input that goes to pin 1 on the mic connector thats also connected to ground?
as i said, my head is a bit simple this morning so not in full control
Iain
And call me crazy, but is the pin 1 on the PCB for input and output connected to nothing at all, other than the pad itself?
Matt[/quote]
:?:
my son was 18 yesterday so i have my thick head on this morning, but do you mean the wire from pin 1 on the mic input that goes to pin 1 on the mic connector thats also connected to ground?
as i said, my head is a bit simple this morning so not in full control
Iain
3nity
Well-known member
http://www.diyfactory.com/projects/fetboy/fetboy.htm
Do you have all the transistor placed in the good way?
Caps? ???
Power supply is fine?
For grounding you should go from pin 1 XLR to star ground.
I'm finishing mines this week too if everything goes fine!
Do you have all the transistor placed in the good way?
Caps? ???
Power supply is fine?
For grounding you should go from pin 1 XLR to star ground.
I'm finishing mines this week too if everything goes fine!
fucanay
Well-known member
[quote author="lofi"][quote author="fucanay"]
And call me crazy, but is the pin 1 on the PCB for input and output connected to nothing at all, other than the pad itself?
Matt[/quote]
:?:
my son was 18 yesterday so i have my thick head on this morning, but do you mean the wire from pin 1 on the mic input that goes to pin 1 on the mic connector thats also connected to ground?
as i said, my head is a bit simple this morning so not in full control
Iain[/quote]
I mean the pad in these pictures looks like it's not attacked to the ground plane. And don't worry about the thick head, it happens. Currently to me too.
Matt
And call me crazy, but is the pin 1 on the PCB for input and output connected to nothing at all, other than the pad itself?
Matt[/quote]
:?:
my son was 18 yesterday so i have my thick head on this morning, but do you mean the wire from pin 1 on the mic input that goes to pin 1 on the mic connector thats also connected to ground?
as i said, my head is a bit simple this morning so not in full control
Iain[/quote]
I mean the pad in these pictures looks like it's not attacked to the ground plane. And don't worry about the thick head, it happens. Currently to me too.
Matt
fucanay
Well-known member
[quote author="3nity"]http://www.diyfactory.com/projects/fetboy/fetboy.htm
Do you have all the transistor placed in the good way?
Caps? ???
Power supply is fine?
For grounding you should go from pin 1 XLR to star ground.
I'm finishing mines this week too if everything goes fine![/quote]
Transistor are in the right way. I think the power supply is ok, I mean, I have the right voltages.
For the overall grounding scheme, I have IEC ground pin to chassis and Input XLR pin 1 to the same point on the chassis. When that didn't work, I added the sleeve of the Output TRS and that didn't work either.
I'm going to look at it with fresh eyes this morning and I'll take photos if I can't figure it out.
Matt
Do you have all the transistor placed in the good way?
Caps? ???
Power supply is fine?
For grounding you should go from pin 1 XLR to star ground.
I'm finishing mines this week too if everything goes fine![/quote]
Transistor are in the right way. I think the power supply is ok, I mean, I have the right voltages.
For the overall grounding scheme, I have IEC ground pin to chassis and Input XLR pin 1 to the same point on the chassis. When that didn't work, I added the sleeve of the Output TRS and that didn't work either.
I'm going to look at it with fresh eyes this morning and I'll take photos if I can't figure it out.
Matt
lofi
Well-known member
Would you ming arrowing the pad your on about Matt please
fucanay
Well-known member
Ok, I must just be crazy on that pad, because I figured out the problem. Which was a short between the PSU and it's mounting hardware. putting some plastic washers in there fixed the hum. There is a little 60hz down at around -85db, which is pretty low I guess.
This sucker does still oscillate at the highest gain setting. I'm going to read back in this thread to see if the fix was there for that. I think I remember there being some about adding a cap or removing a cap or something.
Sorry about my dumbness.
Matt
This sucker does still oscillate at the highest gain setting. I'm going to read back in this thread to see if the fix was there for that. I think I remember there being some about adding a cap or removing a cap or something.
Sorry about my dumbness.
Matt
fucanay
Well-known member
Ok, here is another strange thing. When I have the fetboy plugged into my RME Fireface with the power on, everything is fine. If I turn it off, a 60hz hum grows gradually until it is pretty loud. However if I do the same thing plugged into the Behringer ADA, it doesn't do that at all. Anyone have an idea on what could be causing it?
As far as the other stuff goes, I'll be taking C1 out, as even before the bad oscillation, this thing has plenty of gain for my SM7. If that doesn't totally fix the oscillation, I'll through the resistor off the wiper on the gain pot. And, I'm going to order some more 2N5457 to get my voltages a little closer, which mine weren't so much. I think I matched a pair of 13.1V and 12.9V on the other channel using the fairchilds. Sound good?
Matt
As far as the other stuff goes, I'll be taking C1 out, as even before the bad oscillation, this thing has plenty of gain for my SM7. If that doesn't totally fix the oscillation, I'll through the resistor off the wiper on the gain pot. And, I'm going to order some more 2N5457 to get my voltages a little closer, which mine weren't so much. I think I matched a pair of 13.1V and 12.9V on the other channel using the fairchilds. Sound good?
Matt
fucanay
Well-known member
I pulled C1, no noticeable difference in oscillation. The only 2 watt resistors I have are 470R, so putting that between the wiper and the gate seems pointless. I don't really know what to do with it at this point.
On top of al of that my PSU is still running too hot. The transformer puts out 28.7VAC, rectifies to about 40VDC then having to regulate it down by about 16 volts is getting that thing hot. Now, I read in another thread about putting a resistor in before the regulator to drop the voltage the regulator sees, but I'm having a hard time figuring out my current consumption to fit in the formula I found. Could someone explain to me how I should check that? I'm starting to think that this modified Green Pre PSU wasn't worth the trouble I'm having with it. I think the problem I'm having is using to toroidal in series and it's doubling the the amount that the voltage is over spec and forcing me to regulate too far down.
Matt
On top of al of that my PSU is still running too hot. The transformer puts out 28.7VAC, rectifies to about 40VDC then having to regulate it down by about 16 volts is getting that thing hot. Now, I read in another thread about putting a resistor in before the regulator to drop the voltage the regulator sees, but I'm having a hard time figuring out my current consumption to fit in the formula I found. Could someone explain to me how I should check that? I'm starting to think that this modified Green Pre PSU wasn't worth the trouble I'm having with it. I think the problem I'm having is using to toroidal in series and it's doubling the the amount that the voltage is over spec and forcing me to regulate too far down.
Matt
3nity
Well-known member
Are you using a 24-ov-24 transformer?
i;m using a 12-0v-12v one and still i havent tried it!
i;m using a 12-0v-12v one and still i havent tried it!
fucanay
Well-known member
I'm using the 12-0-12. I put a 10R 1 watt resistor between the positive leg of the rectifier and the place where that leg is supposed to enter the board and it used up about 8 volts (from ~ +40 to ~ +32). I'd like to use up a little more voltage, but I can't find any resistors locally. I hate Radio Shack. They have almost nothing of use.
Matt
Matt
fucanay
Well-known member
Update: I put another 10R 1 Watt resistor in series, for a total of 20 ohms, and it's a 28.5 VDC now. Should be pretty good now. It's at 40º C when it's max temp is 125º C. I think I'm happy with that. On my next parts order I'll get a 20ohm 2 Watt resistor to put in there and I'm still putting small clip on heatsinks on both regulators just to be on the safe side.
Now to fix the other problems. Oscillation, Noise with the power shut off, etc.
Matt
Now to fix the other problems. Oscillation, Noise with the power shut off, etc.
Matt
fucanay
Well-known member
This is what it sounds like when I turn up the gain pot too far.
http://www.fucanay.fischerworks.com/diy/fetboy_osc.mp3
This is what it sounds like if the track is armed but the fetboy's power is turned off.
http://www.fucanay.fischerworks.com/diy/fetboy_power_off.mp3
Any ideas on how to fix either of these? Should I change my gain pot from 10k to something else?
Matt
http://www.fucanay.fischerworks.com/diy/fetboy_osc.mp3
This is what it sounds like if the track is armed but the fetboy's power is turned off.
http://www.fucanay.fischerworks.com/diy/fetboy_power_off.mp3
Any ideas on how to fix either of these? Should I change my gain pot from 10k to something else?
Matt
