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Old 30th December 2013, 04:58 PM   #1
acumos is offline acumos  Italy
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Default f5 no voltage through R11 R12

Hi to all. I've built my new F5 power amp but I can't measure voltage through R11 and R12. I've found few errors Q5 and Q6 were placed in ebc cbe wrong position and my soldering iron had 30-40v on the tip. The rail voltage is ok 23.5v. Is the ground wiring important in this step. Can an error in grounding affect the voltage? Following a guide I've added 2.2k resistor to R3 and R4 but...
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Old 30th December 2013, 05:21 PM   #2
Zen Mod is offline Zen Mod  Serbia
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post exact schematic you're reffering to

your soldering is somewhat messy - wires needs more solder , additional resistors aren't looking as soldered at all

besides that - with repeated color of wires , one need to have extensive experience , to not mix things

confirm both PSU polarities present on pcb , same as proper gnd from PSU

confirm that you mount functional Jfets on pcb ;

from where you purchase them ?
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Old 30th December 2013, 05:43 PM   #3
acumos is offline acumos  Italy
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cviller 2.0 boards and JojoD818 build guide;
about the colors in this step I'm wiring only v+ v- gnd
Are you coming out from my usb port? Now I do have voltage and mosfet are warming!!!
Perhaps I really needed more ohms and at first the resistors were badly soldered. Now when I put full voltage to the board the voltage through r11 starts from 0.3v and rapidly goes up to 0.5. Then I disconnected the voltage cause the trans are not heatsinked. I have to solder the resistors to mount the board. Can I keep these resistors values?
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Old 30th December 2013, 05:52 PM   #4
Zen Mod is offline Zen Mod  Serbia
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keep new resistor values - trimpots are dominative

check all solder points , check isolation of mosfets from heatsink , when you finish mounting

be sure that they're screwed firmly

find any of F5 biasing procedure tutorials , and read it several times - please

ground inputs during entire setting procedure
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Old 30th December 2013, 07:02 PM   #5
acumos is offline acumos  Italy
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Ok now with only 8 turn I have 0.5v Is it normal that if I measure the output from psu with board disconneted I have 23.5v and when I plug the board I see 22.5?
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Old 30th December 2013, 07:05 PM   #6
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when you are higher :

-standing free and looking in Venezia direction ,or
- doing the same , with 50kg sack of cement , on shoulders ?

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