if you change R33 = 22R, the V-out is still that, you can change trimmer 200R bay 500R or 1K!
Quanghao
From the source to the gate of the second fet, i get the same voltages as the outputs. Surely this is incorrect?
The design by salas says it should be 4.07v across them...
http://www.audiodesignguide.com/DACend2/Sala-shunt-for-DAC.jpg
Which in turn leads me to think that something is wrong with that drivers part...
What v drop should we be getting across the led's?
Apellizo if you have your voltages about right ~5.5v. Could you possibly check the voltages you get around that part of the board.
Thanks.
The design by salas says it should be 4.07v across them...
http://www.audiodesignguide.com/DACend2/Sala-shunt-for-DAC.jpg
Which in turn leads me to think that something is wrong with that drivers part...
What v drop should we be getting across the led's?
Apellizo if you have your voltages about right ~5.5v. Could you possibly check the voltages you get around that part of the board.
Thanks.
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If you use a 470R as test dummy load, then 10mA will be running to the dummy, rest to the shunt mos element. If it works like that with measurable Vgs circa 3-4V, there is nothing malfunctioning in the reg itself. The thing here is that a shunt reg feeds many little shunt regs at about the same set voltage. See what is the consumption by using a dvm in series current mode when feeding the DAC board directly from the main filter cap with crock clips also. Is the running current you set enough so the shunt mosfet has at least +20% to work with so not to cut off? Maybe you have consumption differences between builds and some are asking beyond your typical CCS settings? I am afraid that the TLs rob the main CCS current and set the voltage themselves, starving the main mosfet. Vdrop across the Leds should be their number X individual Vf.
Salas, i think you are right. my build showed around an 85ma pull from the dac board without chips in, so we should be lookign at 115ma+ which is what.... 2.2/r = 0.120, R= 18ohms minimum max?
I have a couple of 33r in parallel so 16r, and its still close...
but as i said, if you adjust to say 5.15 so vgs comes up, the tl431 still do the job (albeit adding there own noise), they dont want much overhead. I'll try going downt 10r or 8r to put a bit more current through the shunt mos.
I have a couple of 33r in parallel so 16r, and its still close...
but as i said, if you adjust to say 5.15 so vgs comes up, the tl431 still do the job (albeit adding there own noise), they dont want much overhead. I'll try going downt 10r or 8r to put a bit more current through the shunt mos.
Thanks for your input Salas. I just pulled out my wire from the shunt to the dac board, i popped my multimeter in place of it and got 64ma across the digi 5v without the chips in.
Hmmm... So if thats the case, or like adamus, can you think of any explanation of why the vgs of the second fet is 0 (when only a single 27r is used, considering i always get 3.5+v across the second fet on the +5v analog, considering they're identical?
Is it just as the tl431's are using such a high current draw?
Is it ok to run the fets as low as 5.15v? if they have values above 3.5v for vgs.
Also sorry what is CCS?
Sorry, noob learning.
Hmmm... So if thats the case, or like adamus, can you think of any explanation of why the vgs of the second fet is 0 (when only a single 27r is used, considering i always get 3.5+v across the second fet on the +5v analog, considering they're identical?
Is it just as the tl431's are using such a high current draw?
Is it ok to run the fets as low as 5.15v? if they have values above 3.5v for vgs.
Also sorry what is CCS?
Sorry, noob learning.
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2.2/r is ballpark, measure your individual vdrop across r and divide by r. Use same vdrop for projecting new r. Watch to be conservative with heat.
Hmmmm... after running my PS up for my I/V end I got 250v after about 2 mins.
Is that normal?
It's still increasing but even slower than upto 250v.
I have a 300v input and the fet gets warm, quite warm after only a few mins, however it is well mounted to a sink so the sink gets warm, yet the fet stay relatively cool.
Sound about right?
Is that normal?
It's still increasing but even slower than upto 250v.
I have a 300v input and the fet gets warm, quite warm after only a few mins, however it is well mounted to a sink so the sink gets warm, yet the fet stay relatively cool.
Sound about right?
My resistors are smelling like paint on my I/V board. They read 11.64K (4 x 47k paralleled)
So it's not too far off ~11.75.
Is it bad that they smell, they don't smell a huge amount, just a lil wiff of paint after a few mins of operation. No 6.3v connected, nor valves in.
As soon as i smelt it off it went. I've never worked on anything from scratch before, so do resistors having some considerable power through them smell to start off with? It's not like the burnt resistor smell, which i've smelt before...
I guess my voltage out of my supply is too high, right?
So it's not too far off ~11.75.
Is it bad that they smell, they don't smell a huge amount, just a lil wiff of paint after a few mins of operation. No 6.3v connected, nor valves in.
As soon as i smelt it off it went. I've never worked on anything from scratch before, so do resistors having some considerable power through them smell to start off with? It's not like the burnt resistor smell, which i've smelt before...
I guess my voltage out of my supply is too high, right?
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