quick question about R3x and R6x values based on Q2,3,5x IDSS values
it the build guide, the following values are mentioned:
normal; R3x=9.1K ;R6x=22R
high; R3x=6.2K ; R6x=33R
in the KIT (from the first page of the thread:
normal: R3x=9.1K ;R6x=33.2R
high; R3x=6.2K ; R6x=27.4R
which values should I choose for "normal"?
thank you
it the build guide, the following values are mentioned:
normal; R3x=9.1K ;R6x=22R
high; R3x=6.2K ; R6x=33R
in the KIT (from the first page of the thread:
normal: R3x=9.1K ;R6x=33.2R
high; R3x=6.2K ; R6x=27.4R
which values should I choose for "normal"?
thank you
If your Q2x are 3-4mA IDSS use the 27.4R. If around 5mA IDSS use the 33.2R. If you delta button your DMM while having your probes shorted first, and then remeasure, they are probably 27R & 33R components. I would suggest you use the R3x 9.1k anyway and if this gives you a bit more max range it should still be within the control of VR2x
There is also the unknown DMM tolerance + last digit uncertainty spec which maybe tricks us that the components are coming from a more detailed range. Those are fine there anyway since the Q2x IDSS chance and its degeneration for keeping its dissipation lower is an approximation
I suspect that many of our builds would work with ±10% resistor values.
It's rare that we actually need very tight tolerances for resistors.
But we do need to learn how to use what few instruments we have at our disposal.
Just reading the DMM digits is not always reliable.
It's rare that we actually need very tight tolerances for resistors.
But we do need to learn how to use what few instruments we have at our disposal.
Just reading the DMM digits is not always reliable.
It depends on each circuit's nature. In this phono for instance which has no loop feedback the tight selection and matching weight falls on the shoulders of JFETS & LEDS to have good channel gain agreement but for its RIAA filter portion falls on the shoulders of film capacitors and resistors again
Salas, firing up a simplsitic based on documentation on page 1. Not sure if there are revisions. On one channel, Jfet ccs Q2x and Q3x are functioning properly, the Q1x is passing appropriate current, but i have no adjustablity on shunt regulator. Q6x is dropping full rail voltage. Does this mean it is cooked or is there an issue with its reference? I always forget how Q4x and Q6x intereact.
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It may happen with MOSFETS if not wearing grounded wristband but not all the time. I am playing with them on breadboards grabbing them by the pins many times, but that one time it was dead just after assembled. Alright, DIY fun assembly standard, its not for NASA use anyway
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