As removed from a lovely Champagne Marantz Stereo Amplifier Model: PM 310
These are all of the front panel potentiometers, 2x slide/fader pots and 2x rotary pots
These are pretty specialised pots, especially the rotary type - please read my details below
Offered as spare parts for the PM 310 OR possibly other Marantz or non-Marantz equipment. I have provided some detail that may help decide if these could be used in other equipment.
Marantz Stereo Amplifier SPARE PART ONLY
Model: PM 310
Marantz part # various
Potentiometers
2x slider pots MOUNTED on a PCB (PE00/K207H1650) 50K C curve each
1x rotary pot 200K B curve
1x dual rotary pot 100K B curve
The rotary pots are NOT your ordinary "3 leg" variety, see below about this
ORIGINAL FUNCTION: BALANCE CONTROL
Alps Japan
Part # RK02040110
1/4" fluted shaft 23mm
Body diameter: 15mm
PCB mounting
200K rotary pot (B curve) with a centre tap
Pot rotation is physically indented in the middle of travel (at the centre point, the shaft drops into a small recess which does not lock rotation but provides positive tactile feedback to the user that this centre point has been reached e.g balance between two audio signals, left and right.
Think of this as a normal pot with a fixed resistance track but with a centre tap provided. The wiper then runs the full length of this fixed resistance track. You end up with a variable resistor which has 3 (not the normal 2) points at which the resistance between the wiper and the fixed track is zero (or close to it).
This is why the pot has 4 connection points, not the normal 3.
I actually made a few resistance tests to see this in action, the actual readings I obtained were:
Full fixed track resistance 179K Ohm
Centre tap point resistance 89K Ohm
As the wiper is moved from one end of the fixed track to the other end, the resistance changes smoothly (no flat spots)
Based on my "real life" measurements, this pot has a value tolerance of around 10% (actual indicated resistance is 200K)
ORIGINAL FUNCTION: VOLUME CONTROL
Alps Japan
Part # RM01040400
1/4" fluted shaft 23mm
Body diameter
100K dual rotary pot (B curve) with centre taps (4 connection points)
As the shaft is rotated, there is tactile feedback in the form a soft but definite indents. This allows for a positive feel as the pot is rotated and corresponds with the multitude of dB points indicated on the front panel Volume scale - there are actually 40 small indents as the pot is rotated. This indenting is achieved by a special mechanical arrangement at the rear of the pot.
I made real time resistance tests of this dual pot and the results were:
Front pot
Full fixed track resistance 83K Ohm
Centre tap point resistance 44K Ohm
Rear pot
Full fixed track resistance 81K Ohm
Centre tap point resistance 43K Ohm
As the wiper is moved from one end of the fixed track to the other end, again the resistance variation occurs smoothly and without any flat or dead spots
This dual pot appears to be slightly out of spec if it is supposed to be a 10% tolerance pot as the lowest track resistance should be around 90K Ohm, but my assumption of a 10% tolerance could also be incorrect!
DUAL SLIDER POTS: TREBLE & BASS CONTROL
These are mounted on the PE00 board, also populated with passive components - there are no semiconductors on this board.
The original flying leads remain intact and were desoldered from the main board (or removed from the wire-wrap post)
NOTE: Construction techniques used at the time mean't that a lot of connections were wire wrap. Some of the flying leads are solid core wire wrap but can still be soldered instead of installing using wire wrap techniques (you can still get wire wrap tools from the likes of Element 14)
I have now safely sealed all of these components in plastic to maintain their present condition and keep out dust/dirt.
