INFINITY P-FRPRELUDE
Service Manual

Composition P-FR (Prelude)

Service Bulletin
Service bulletin INF9708 - Dec. 1997 To: All Infinity Service Centers This is considered a Major repair Models: Composition Prelude P-FR Subject: Speaker receives radio stations In the event you receive a Composition Prelude P-FR with the complaint of �speaker is picking up radio stations by itself�, perform the necessary steps listed below to add a simple filter network to the amplifier(s): 1) Unplug all input and power cables; lay speaker face down on padded surface. No grille removal is necessary; speaker terminal should be pointing straight up in the air. 2) Remove the (2) large flat head Phillips mounting screws at the bottom of the amplifier. 3) Pull the amp assembly off the speaker cabinet; moderate force may be required to �break� the gasket seal. 4) With the amp assembly loose (and wires exposed), unplug the mini-stereo plug from the amp body. With a jeweler�s or small screwdriver, loosen the four small screw heads so the four output wires can be removed from the connector. NOTE: It is not necessary to completely remove the screws to detach the wires. 5) With the amp assembly free and on a work bench, slide out and remove the bottom cover to expose the circuit board; you may have to loosen the (4) Phillips screws on the end plate, control side, and tap the board out of its slot to accomplish this. 6) Loosen and remove the 3/8� nuts holding the main (elevated) circuit board in place. 7) Pull circuit board assembly out of the amplifier case; it may be necessary to unplug connector CN603, the speaker connector (red/white wires) to be able to manipulate the board during modification. 8) Locate IC604 (uPC1298V); it�s attached to the heatsink. Modifications will be near this IC, above and under the board. 9) Identify area on the solder/trace side of the board, in the area of where the IC604 pins are. See drawing. 10) Solder a 220pf ceramic disc capacitor (Infinity part # 210-3907) across pins 4 & 5; insulate exposed leads on the capacitor with sleeves or tubing so they don�t touch adjacent connections on the board. 11) On the component side of the board (See drawing), remove and replace Jumper 645 with a 390 uH Inductor (Infinity part # 499-4313). This can be accomplished by desoldering and removing the jumper wire from it�s location (and replacing with the inductor) - or by cutting into the middle of the jumper wire and �inserting� the inductor. Insulate exposed leads on the inductor with sleeves or tubing so they don�t touch adjacent connections on the board. 12) Attach connector CN603; replace circuit board back into inside cover; replace and tighten the three 3/8� nuts; replace bottom cover, replace end panel if loosened. 13) Re-attached amplifier assembly onto speaker cabinet in the reverse order mentioned above. OBSERVE POLARITY on main speaker wires: MF (midrange): White to (+), White/stripe to (-) LF (woofer): Red to (+), Red/stripe to (-)