⚙️ MCINTOSH MC402
power amplifier · technical digest
Field-collected data and original specifications for professional diagnosis. Official service bulletins are not public; the following is compiled from technical discussions and manufacturer documentation.
Common complaint & field‑issue analysis
🔹 Ground loop hum
Documented interaction with preamplifiers (e.g. C46). A McIntosh engineer emphasised: verify all components on same electrical phase before any ground isolation — safety ground must remain intact.
🔸 EPJ94VO board failure
One specific failure mode traced to EPJ94VO (Rohs 129711 - Rev. A). Symptom: audio drops / diminishes after ≈1 hour, first one channel then the other → points to thermal or failing component on that board.
Capacitor selection · original specifications
🔬 original design:
precision metal film resistors and low dielectric absorption film capacitors in all critical signal paths.
📋 replacement strategy:
McIntosh explicitly requires parts either specified by McIntosh or with identical characteristics as original. Unauthorised substitutions can pose safety hazards.
🏭 best practice:
Contact us directly
ⓘ low dielectric absorption film types are critical — maintain original philosophy
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Safety protocol
⚠️ no user‑serviceable parts internally
Standard safety protocols require a full operational safety check post‑service to ensure the product is in proper operating condition, as stated in the original manual.
🔒 Tek Media Group follows all manufacturer safety guidelines.
For further model-specific inquiries or parts sourcing, contact McIntosh directly. This document is for internal technical use.
