green pre : problem with the led-meter

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ricothetroll

Well-known member
Joined
Jul 5, 2005
Messages
325
Location
Bruxelles
hi, i built a 4-channels green pre. everything works fine, excepted the led meter of one of the preamps (everything works on this preamp excepted that).

i built the v14 of the green pre.

i tested a few things but didn't manage to find where the problem is:

- i changed the 4 leds

- i switched the tl074 and the lm339 with another preamp : the other one works still fine and the problematic one still doesn't work

- i measured the voltages on the pins of the tl074 and the lm339 and some aren't the right ones : pin 11 of the tl074 and pin 1, 2, 12, 13, 14 of the lm339.

as i found no scheme of the v14 i don't know exactly which parts of the circuit are concerned with the led meter. of course, i compared the problematic circuit with the 3 others but i found no difference...

can someone help me with this?

thanx a lot.
 
Pin 11 of the 074 is the + power rail. What does it read?

Trace back from pin 11 & make sure the 2 10R resistors are in circuit. Do a DC resistance check from pin 11 back to the +ve voltage rail, should be about 20R

Peter
 
that was it! there was a bad soldering just after the second 10R resistor and that's why the tl074 wasn't powered correctly! now it works fine.

thanx a lot for your help, peter!!!! :grin:
 
Hello guys, i just finished the green pre ver14 and i have a problem with the led meter

all the leds are on, not full power and from brighter to darker more or less

any advice?

i saw in the thread somebody else got the same problem but i didnt see any resolution

thanks
 
> ...i didnt see any resolution

ricothetroll said:
there was a bad soldering just after the second 10R resistor and that's why the tl074 wasn't powered correctly! now it works fine.
 
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