Dx Blame MKIII-Hx - Builder's thread

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#2,061
AndrewT said:
R17 is not a signal current. Connect it to the Power Ground (the other end of R31).

If the Q7 is passing the correct current (~1mA) then R17 will also pass ~1mA.
It should drop ~1V
P = IV = 1*0.001 = 1mW
It can't burn out.

It is there to prevent Q7 burning out.
Click to expand...

Hi Drew,

Thanks for the info....

bonfis said:
Hi Willy-
I made this mod also and had no problem with R17. It doesn't make sense that moving that end of R17 from the lifted signal ground to main ground could cause the problem. You are only reducing the resistance from collector to ground by 10 ohms (1%). I think you must have a wiring error or short somewhere. Are you sure you cut the correct trace?
Steve
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Hi Steve,

Yes I’m pretty sure I cut the correct trace, anyway let me try once more tonight I might miss somewhere that causing this error….

Thanks Steve.

Regards,
Willy
 
#2,062
#2,063

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#2,066
Hello guys 😀

This is a bit crazy what I'm doing right now but I will post it any way, this is an old layout I did last year and I never have the change to try out is basically Dx Blame MKIII same circuit that Carlos design already I just want it to try different style layout.

What I have in mind about the layout is the distance between main power transistors so this might change later on, also the fuses I also have to relocate them too, any way this is my project to have fun 🙂.




Regards
Juan
 

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#2,070
I see on this layout that the only thing on the lifted ground is the input itself. I also notice that the ground runs continuous around the entire board. I see like 5 different locations for attaching to ground. I don't know a lot about it but since I had trouble getting rid of ground hum issues on my boards I look for that. It will be interesting to see if this ground scheme fixes it.

Blessings, Terry
 
#2,071
still4given said:
I see on this layout that the only thing on the lifted ground is the input itself. I also notice that the ground runs continuous around the entire board. I see like 5 different locations for attaching to ground. I don't know a lot about it but since I had trouble getting rid of ground hum issues on my boards I look for that. It will be interesting to see if this ground scheme fixes it.

Blessings, Terry
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Hi Terry well the design from mister Carlos I simulated many times and respond really well I fallow all tips and I have been going back and forward reading all changes I still using Carlos schematic as always the only thing I did is add one more pair and also I increase the voltage a bit 75V supply.

Juan
 

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#2,072
Hi Terry,

If I turn this resistance 8k2 as shown on picture and cut the tracers and make the 2 jumpers then it is good?
I'm asking just for the security so I make no error.
Tomorrow I make this modification, and hear if the hum is away 😉

Regards,
Rudy
 

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#2,076
Hi Rudy,

Yes, that is exactly what I did. That makes the PCB match the schematic. I still have a very slight hum but it is very slight. Not noticeable unless you are very close to the speaker.

Hi Juan,

You say you have no hum. Is you amp mounted in a case with earth ground attached? Mine didn't hum until I put it in a case. Even then it didn't hum without something attached to the input. It took the modifications that Rudy is showing to get rid of it. As I said, with those mods, it matches the schematic.

Blessings, Terry
 
#2,078
still4given said:
Hi Rudy,

Yes, that is exactly what I did. That makes the PCB match the schematic. I still have a very slight hum but it is very slight. Not noticeable unless you are very close to the speaker.

Hi Juan,

You say you have no hum. Is you amp mounted in a case with earth ground attached? Mine didn't hum until I put it in a case. Even then it didn't hum without something attached to the input. It took the modifications that Rudy is showing to get rid of it. As I said, with those mods, it matches the schematic.

Blessings, Terry
Click to expand...

I never has the chance to have it in a chassis yet, probably is because the magnetic waves from the toroid transformer or earth problems affect yours, did you rated the toroid ? I read a long time ago that on building amps the toroid has to rated to specific way to keep magnet waves to it lowest level possible.

Juan
 
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