UPGRADE (November 2003):
GROUNDING MOD FOR HP-101

PURPOSE: To lower hum on Langevin HP-101 and HP-112 headphone mixers.  

METHOD: To add two ground wires.

UNITS AFFECTED: Serial numbers for units that will benefit from this update are

Langevin HP-101 MODELS: LHPE286 (9/2001) through LHPE332 (9/2003) 8 CHANNEL MODELS
AND
Langevin HP-112 MODELS: LHP2011 (4/2001) through LHP2028 (10/2002) 12 CHANNEL MODELS.

UPDATE KIT INCLUDES:

a)       1 X 7" 16 AWG WIRE 

b)       1 X 3" 16 AWG WIRE 

c)       Instructions and drawings for procedure  

NOTE: if you have some 16 AWG or heavier wire in your shop, you can use that.

TOOLS REQUIRED:

a)       Phillips #1 screwdriver  

b)       15 MM SOCKET W/ RATCHET, or Adjustable Spanner wrench

b)       Wire strippers 

c)        Soldering Iron and solder

PROCEDURE:

1. Disconnect AC power from the power supply unit. 

2. Disconnect 4-pin power supply connector from audio chassis.

3. Remove the bottom cover 4-40 x 1/4" panhead screws using a phillips screwdriver. There are 3 screws on the rear of the unit, three screws towards the front top of the unit, and two each screws on each side of the unit to remove. On the side panels, there are four screws on each side. You must only remove the screws located closest to the corners. Do not remove the middle two screws as these secure the power amplifiers and the regulators to the chassis and these must not be removed. Next use an adjustable spanner or 15mm socket wrench to remove the four nuts on the output 1/4" jacks. Place all your screws, washers, and nuts in a safe place. Now you may slide the bottom cover off towards the front of the unit to clear the headphone jacks. Put cover aside.

4. Referring to the photo below, you want to add the two wires. They are shown as purple wires in the photo. It is recommended to use your multimeter to "beep" through continuity (check for zero resistance) to make sure these wires are indeed going to be soldered to ground and not something else.

5. Use the 7" wire to go from the ground leg of the negative power supply capacitor to the ground related
to the input number 1 circuit. From there, join the 3" wire to this point to the ground on the 7815CV positive regulator circuit where the other existing ground wire is. Follow what is shown below in the picture below.

6. Replace the top cover in the reverse order that you removed it being careful not to hurt the regulators and power amplifiers insulating material on the sides and you are done..

That’s it! No further adjustments or calibrations are necessary.

For further info or to order this kit, please contact our service department.
If you would like to send your unit in and have Paul perform this upgrade for you, please contact him at the address below:

Location of this page online: 

http://www.manleylabs.com/techpage/HP101GROUNDMOD.html