All things Green Pre

[3nity]

of course on the bench work! :grin:
gotta work on the rack now..

 

[Jonkan]

Two of my green pre meters light up one led after i have had the unit running for about half an hour. Even when theres no signal present.

Do i need to adjust the peak meter dc offset or what?

/J

 

[peterc]

Jonkan

Have you done the meter calibration (20k) trimmer?

P

 

[3nity]

PeterC could you give some where to star troubleshooting this pre??
phanton when engaged make this big and loud noise???like a 80's synth!
I will look at it once again.

cheers

 

[Jonkan]

Yup, i calibrated the meters as good as i could.

The problem starts after the unit has been on for half an hour or so.

/J

 

[peterc]

Jonkan: The offset trim is quite fine. Wait for an hour or so after powering up, & then trim the 20k to read -10mV.

3nity:

Does it sound like a Moog or an Oberheim? :green:

Is your phantom 48v? What is the ripple on the Phantom? Check the polarity of the input caps.

Peter

 

[3nity]

A cheap CASIO :green:

 

[3nity]

btw: Phantom i got 37 volts.

 

[peterc]

3nity

What is the Phantom before & after the 6k8 resistors? What is the ripple on it?

Peter

 

[3nity]

37.6v before resistors and 37.4v after. when phantom engaged i have 36.4v.
Is there a problem if my modded my PSU? i did took off a Diode from the 48V i don't remember why! should i put it back??

 

[peterc]

3nity

Do those measurements with a mic plugged in:

The Phantom between the PSU & the 6k8 should be 48v, when the mic is plugged in the voltage between the mic & 6k8 should be in the region of 30-38v.

Peter

 

[3nity]

Peter before anything i'm using your PSU.
Now the trannie i'm using gives me 22v-0v-22v.
Talking phantom section with the three diodes put on place i have 80 volts after the regulator, if i take out one diode i fall to 37 volts.
instead of doing this could i change the resistor values maybe the 8k2???

I wanna do this to talk about the same volts..

 

[peterc]

3nity

If you have 80v AFTER the regulator, then it sounds like the reg is blown. Try changing that first as I'm sure the noise is coming from the faulty part.

Peter

 

[3nity]

Well actually the reg was good i still have the 80 volts... even after changed..don't know!
now i have a problem with the other one, there is no sound i only hear the click when i plug the mic that's it.

 

[3nity]

Peter may the 3 diodes in the multiplier section be tooked apart?? i meant if i have 80 volts after the las diode shoul i take that one and jumper it to have a lower voltage?? maybe other diode model could not multiplied it that much??

 

[peterc]

Well actually the reg was good i still have the 80 volts... even after changed..don't know!

Short circuit maybe?

Peter may the 3 diodes in the multiplier section be tooked apart??

Well, you need 51v or more before the reg, & you said if you take out a diode, there is only 37v. Enough to test phantom mics, but some will not like it.

First things first, get 48v for Phantom

Peter

 

[3nity]

:green: :green: :green: I got it :green: :green: :green:
47 volts!!!!!! arrrrrrg bad soldering on the 8k2 resistor... :roll:

 

[3nity]

Alright Channnel 1 Done thank you Peter, after this i can say those are like your children's you know them well!!
that resistor make so much trouble! aghhhhh( deep breath)

Sounds better than my ex Behringer, better than my 002r pres, and at first conclusions still better than my Sony's MXP channels.
sounds amazing.!!!!!!!

Now channel 2.....no sound.....

 

[3nity]

Peter how comes i can't hear any difference when i engage the HPF switch???

 

[peterc]

Peter how comes i can't hear any difference when i engage the HPF switch???

It is quite a subtle HPF. Try sticking a 60Hz sine through there & then switch it in......

Peter