Tag Archive for MAC4100


McIntosh MAC4100 RCA Jack Replacement PCB (Unpopulated)

This board was created as a solution for replacing the original riveted RCA jacks on the McIntosh MAC4100. The new RCA jacks (CUI RCJ-022 and RCJ-023) are not the most premium connectors in the world, but if your original jacks are loose and intermittent, these will certainly perform better.

Includes one unpopulated PCB and a schematic of the board. RCA jacks are not included, but the part numbers are listed above.

This board is quite involved to install and will require the back panel of your unit to be taken off. Please do not attempt to assemble and install it if you are not familiar with safely diagnosing and repairing electronics. Be sure to take lots of pictures of your original installation so you know where everything goes.

The rivets holding the original RCA jacks in will need to be removed and replaced with #6-32 screws. The board will also need standoffs or spacers to keep it far enough away from the back panel. The original black plastic shrouds can be placed over the new RCA jacks so that the green PCB is not seen from the back panel. (Please see the installation photos above).

Depending on the serial number of your unit, the wiring scheme may be slightly different. This board has the following optional solder jumpers:

  • JP1 or JP2: Short to connect the shields of the “TAPE 1 and 2 IN” jacks to chassis ground (JP1 and JP2 are redundant, use either one)
  • JP3: Short to connect the shields of the “AUX 1 and 2” jacks to chassis ground
  • JP4: Short to connect the shields of the “SCOPE VERT” jack to chassis ground
  • JP5: Short to connect the shields of the “SCOPE HOR” jack to chassis ground
  • JP6: Short to connect the shields of the “PREAMP OUT” and “POWER AMP IN” jacks to chassis ground
  • JP7: Short to connect the shields of the “TAPE 1 and 2 OUT” jacks to the shields of the “TAPE 1 and 2 IN” jacks

For example, in the unit I installed this board in, the shields of the AUX, TAPE OUT, TAPE IN, and PRE OUT/POWER IN jacks were tied to the chassis grounding screw by the factory. This corresponds to shorting JP3, JP1 or JP2, JP7, and JP6. Additionally, there was a 10nF capacitor between the shields of the PHONO jacks and chassis ground, which is implemented as the capacitor footprint C1.