I am based in Tezpur, Assam.
I have a Marantz Stereo Integrated Amplifier, Model - PM-6006, bought in October, 2018.
Last April, there was a crackling noise in the right speaker at low volume, while turning the volume knob.
I trawled the net for a solution and settled for one offered by bengrain, a forum member of
www.vinylengine.com for his PM-6004.
The Volume Pot of the PM-6004, PM-6005 & PM-6006 are similar, being mounted on a separate PCB (pic).
The forum solution involved taking out the Volume Pot with the PCB out of the PM-6004 Amp cabinet & drilling a 2mm hole centrally on top of the black plastic casing of the Gear/Clutch Reduction Chamber (pic #1) of the Volume Pot.
Access is now possible for spraying the cleaner (AEROL Contact & Component Cleaner Spray, made in New Delhi)(pic #5) into the Gear/Clutch Chamber through the newly made hole. The Gear Reduction system (via a Drive Shaft with rectangular cross section) transmits the rotation of the remote operated motor to the D-shaft outside the amplifier cabinet, on which the volume knob is mounted.
However, this ‘phoren’ (UK/USA?) solution did not work for me and I got the Volume Pot replaced with a new one from M/s Audiocrafts.
Subsequently, I dismantled the old Volume Pot and found that it consisted of the following parts (starting from the drive motor side) :
1. Motor assembly mounted on a metal bracket
2. Clutch/Gear Reduction Assembly and motor drive shaft with rectangular cross section (motor side),
3. Metal spring contacts mounted on the motor drive shaft (Resistor Pad side)(pic #4)
4. Potentiometer Resistor Pad (motor side) with 8 pins (front plate side), with the motor drive shaft passing forward through the internal bore of the Resistor Pad,
5. Knob assembly (with ‘D’ section of 25 mm for external knob) locks into the motor drive shaft vide its matching rectangular internal aperture
6. Front plate.
The fun started when the crackling noise reappeared in the right speaker of my system, even with the newly installed Volume Pot. IMHO, access for the cleaner spray is more required on top of the second plastic black casing. I drilled a small hole of 1mm centrally (pic #2) on top of the second plastic casing opposite to the contact surface of the Variable Resistor Pad. Drilling was done carefully, so that the drill did not touch the concentric Resistor Pad contacts, which output the audio signals through the eight pins on the plastic casing. Care was also while drilling the depth of the hole (pic #3), to avoid the drill traveling too deep while drilling and damaging the outermost Metal Spring contacts inside the Chamber.
Make of Portable Drill Machine used : VERILUX
Model : MD3.6LI,
Drill bit sizes used : 2 mm for first hole, 1 mm for the second hole.
Using the spray nozzle pipe supplied with the cleaner, I sprayed a couple of bursts in through the newly made 1mm hole (pic #6) and then used the knob to turn the pot back and forth about 50 times. Thankfully, I was successful this time, with pristine sound coming from both the speakers.
BTW, I am a retired Mechanical Engineer. Am uploading my ‘Made in India’ Jugaar, so that all long suffering Marantz PM-6004, PM-6005 & PM-6006 owners can benefit from it and save their time and money by not getting a new replacement Volume Pots (from M/s Alps Alpine, Japan) for their old repairable ones or a new Stereo Integrated Amplifier even.
