K-Tronix Electronics Repair

Detailed Service Report

Customer: Mark Rozett
Unit: KLH Amplifier
Model: 62U6 - E112521
Invoice: SQ8351075

Reported Issue

Customer reported the unit would only emit a 400 Hz hum when powered on, with no audio output.

Diagnostics & Findings

Initial testing confirmed the amplifier powered on but remained stuck in protection. The protection relay would not switch out of protection, preventing normal output. Low-voltage supply testing showed the 15 V regulation section was out of specification, contributing to instability in the protection/preamp supply.

Further inspection revealed a welded relay condition on one channel and an additional failure in the relay drive / protection support components.

Work Performed

  • Replaced all electrolytic capacitors on the power supply board
  • Identified relay fault: protection relay contact welded on one channel
  • Confirmed protection circuit was not releasing (no relay switching out of protection)
  • Tested 15 V rails and measured +16 V and -14 V (out of specification)
  • Tested 15 V biased/steering diodes and found them out of specification
  • Installed +12 V and -12 V regulators to replace the out-of-spec 15 V biasing network, reducing thermal stress and preventing the preamp section from running excessively hot
  • Protection still did not release; traced fault to the diode across the relay coil
  • Found relay coil diode failed; replaced with a standard rectifier diode
  • After diode replacement, protection released normally and audio output was restored

Testing & Verification

  • Load-tested at 2 ohms for 1 hour
  • Heat dissipation: within specification during full-duration testing
  • Frequency response: within specification

Current Assessment

The amplifier is now operating normally. The protection circuit releases correctly, relay operation is normal, and stable audio output has been verified under load.

Parts & Cost Summary (All-In)

Labor – Power Supply Rebuild & Protection Circuit Repair $156.50
Parts – Power Supply Capacitors, Regulators, Relay Diode $38.50
Bench / Diagnostic Fee Credit ($89.00)
Return Shipping – USPS (11 lbs) $8.38
Total (All-In) $114.38

Shipping: Return shipping via USPS, package weight approximately 11 lbs. Shipping cost is included in the total above.

Payment

You can submit payment using the link below.

Service Status

  • ✔ Power supply board rebuilt (capacitors replaced)
  • ✔ Low-voltage regulation corrected (±12 V regulators installed)
  • ✔ Relay coil diode replaced
  • ✔ Protection circuit functioning correctly
  • ✔ Load tested and verified within spec
  • ✔ Repair completed

Important Notes

  • Customer contact details (email/phone) are intentionally excluded from this report for privacy
  • Return shipping via USPS ($8.38) is included in the total
  • All measurements and results reflect bench testing at the time of service

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