the sound of frying eggs

[pucho812]

if it's on every module of a desk and can be heard on direct outs, buss outs,  and monitored skipping the master section, we can assume it's a PSU.  old and rickety might be time to replace the lamba that is at least 25-30 years old. the upside is single supply voltage 48VDC @ 17 amps.

 

[gridcurrent]

IMHO, Lambda linear power supplies are worth repairing.
Even though they used high quality capacitors, might be time to check and/or replace.
Easy to determine psu noise with a VTVM and osciloscope, or your audio analyzer.
The LM series should read less than 1 mV  noise  (RMS ripple) under load.
LC and LD series are even quieter.
I could not find any reference of a 48 VDC Lambda linear @ 17 amperes, that would be a monster.

 

[pucho812]

yes... I didn't have an o-scope in the portable kit at the late night emergency call but I would  do that. 
This is a rack mount.  and was installed some time ago. I would agree it's worth fixing,  however the studio is in a bind and they want to replace it asap.  I have loaned them mic pre's for now.
The power supply in question....
Lambda  lmg-48 max output of 17A @ 40 degrees C.
The only  confusing part is that whoever wired it prior to me ever visiting  used the same color of wires for V+ and V-.  To further complicate the issue it's in a rack where physical access is limited. On an initial visit I was having to use my cell phone for photos of the rear as I couldn't get the rack  unit completely out without disconnecting wires I could not see.  So arm over the top snap photo and go from there. 

 

[mjrippe]

Just curious, what is the board that runs on +48vdc?

 

[gridcurrent]

Trident A range operates on +48 VDC.

Lambda LM-g
1300 watts with output loaded,  40 degrees C
72 pounds net
5 3/16"  X  19"  X  16 1/2"

ripple and noise:
1 mV RMS
3 mV peak to peak

load regulation:
0.03% plus 3 mV for load variations
from 0 to full load

 

[JohnRoberts]

Yes PS matter, and can easily be the vector causing noise common to multiple audio outputs.

I am apprehensive about just swapping in random PS, but a mature console model may have other owners with similar experience.

JR

 

[pucho812]

Yes this is an A-range.
I agree jr.

 

[QUEEF BAG]

after repairing the coutant power supply that came with our A range twice  a month for a while
we got an acopian that cranks to 50 volts.

it's been great.

 

[pucho812]

after repairing the coutant power supply that came with our A range twice  a month for a while
we got an acopian that cranks to 50 volts.

it's been great.

yup... a replacement is on it's way...  the desk is getting more refurbishment as budget permits. for example right now the stereo bus is out on one side, so using an external monitor controller.  budget is being  raised to get it back to snuff but it's not there yet.

 

[pucho812]

New supply in and a major drop in noise floor.   Frying eggs was taken care of as well but that was psu and a strip. The upside eco friendly new psu seeems to be quite nice.