We are very behind on posts. To catch up, here are a few McIntosh MC2205 repairs Bob the Tech Audio has done over the past few months. We addressed a number of issues in this first example. The unit had no audio output, which we isolated to a bad speaker relay driver transistor on the power supply. We re-capped the supply and addressed the faulty transistor.
With the relay working, we found the inputs were intermittent. We updated the RCA input connectors with new gold plated ones and disassembled and cleaned the input sensitivity switch. As we reassembled the area we replaced the input coupling capacitors and sensitivity switch resistors. Finally, we replaced a badly delaminated cable between power supply and normal/limit lamp board. We replaced the able with a ribbon cable and friction lock header connectors commonly used in many McIntosh amplifiers. The unit is running reliably now for a happy customer.
Lamps, lighting, loose color gels and diffusers are common issues with amplifiers of this vintage. The tapes get old and dry out and the gels and diffusers end up loose behind the front panel. This example shows the normal/limit gels badly out of place, so when lit the colors shown were all wrong. We reattached the loose diffuser, and the meter gel plexiglass. Bob the Tech reattached all these parts in their proper place and updated all the lamps with fresh ones to last for years to come. We replaced the deteriorated light insulating foam with fresh foam. We also tightened front panel controls on this unit as they had become loose in the chassis.
Intermittent audio is often caused by dirty or failing speaker relays. We disassembled this speaker relay for cleaning. Once cleaned and reinstalled the unit performed reliably in both channels.
No pictures to share this time, but we re-cap and replace out of tolerance resistors in meter, power supply, and driver boards in many of these MC2205 units. This is often required to resolve inoperative meters, and fix failed relay drive circuits and channel-channel output mismatch. If you are having issues with your McIntosh MC2205 and need repairs, contact Bob the Tech Audio.
