McIntosh MAC1700


LAMP REPLACEMENT


Time required: at least an hour.
Tools: long flat-bladed screwdriver, long-nose pliers, nut spinner, 1/4" socket set or very small adjustable wrench.

BA9 LEDs are recommended for this, rather than merely replacing the incandescents.

Lay the tuner on a flat surface, well illuminated, with enough room in front of it to support the dial when folded down.


Remove the full width rectangular cover behind the faceplate (2 hex-head screws on each side, then prise it slightly backwards to release it).


Remove the knobs (push fit) and the nuts on the volume and balance pot shafts, and on the selector shaft etc. if present. Remove the front plate (2 hex nuts at top left and right: you will probably need a 1/4" drive 7/32" A/F or 6mm socket on this). 


The two LH lamps can now be removed via the front with a push and a 1/8 turn CCW, and the opposite to replace them. See picture. No need to remove the lamp mounts. Same for the RH two. No tools required for these.


Remove the small trunnion holding the left-hand dial cord pulley (2 small black hex head screws). Move the dial cord out of the way. Remove the long black plate behind the dial that the dial pointer slides on, covering the eight lamps (2 small black hex head screws). Unscrew 2 hex head screws holding down the black flange that holds the eight lamps.


Unfasten the full-width front dial plate assembly (4 hex head screws) and fold it down out of the way. Lift the flange holding the lamps high enough to clear the thick cables underneath, then fold it top backwards so it is horizontal, then you can get at the lamps via the bottom. See picture. The eight central lamps can now be removed by pushing each lamp up into its base and giving it a 1/8 turn CCW (maybe with pliers), and replaced by holding the base of the lamp with pliers with the lamp in the same orientation as the pliers, base end away, push it up into the socket and a 1/8 turn CW to engage the bayonet fitting.


The meter is self-illuminating and does not have a separate lamp.


Reassemble in reverse order. You will need either a long magnetic screwdriver or a nut spinner to get some of the screws back into position. Take care of the small wires around the 8-lamp assembly, and of the dial cord. The purple and green wires go under and inside the lamp flange, so as not to foul the large tuning pulley. Don't worry about the position of the dial cord on the flywheel spindle: as long as the pointer doesn't move on the cord, its position is correct with respect to the large tuning pulley. 


First replace the lamp housing flange. Then replace the long plate the dial cord slides on, then slide the pointer onto it from the right, then arrange the dial cord under and over the three pulleys on the right as per photo, with the front run of the cord going under the plate, then replace the LH pulley assembly, then gently pull the cord tight against the springs and place over this pulley. The cord runs straight everywhere with no twists. It will probably lay over itself on the flywheel spindle at first, but winding the tuning knob both ways will clear that. Make sure you can tune to both ends of the dial.


(Dial cord stringing: it comes off the flywheel spindle at the right, over the back pulley, around and down the LH side of the tuning pulley, and in to the spring. The other end comes off the spring, up and around the RH side of the tuning pulley to the back of the LH pulley, around it to the left and front, back under the plate via the pointer and around to the front of the front LH pulley, then around to its back via its RH side, over and down around the LH side of the middle pulley, and back to the flywheel spindle. See picture, and the service manual.)


Esmond Pitt
Dada Electronics Australia