Serial Number:FR 6169846 (on label inside)
Year of Manufacture:1983 (83xx latest component date codes)
Date of Receipt:1989
Source:Noticed in surplus room in rear of RP Electronics at 4th Ave. & Arbutus.
State upon Receipt: Good physical condition but major component damage, presumably from reverse voltage application.

Date:1989 Summer
Procedure: Schematic obtained from Ralph's Radio.

  • Fuse blown, replaced.
  • U501 & U551 (TDA2003) audio power amp ICs blown, replaced.
  • U451 (TCA5500) audio preamp IC blown, replaced.
  • U88 (TAA765A) op amp for 9V regulator blown, replaced with simpler single-chip 78L09 regulator, extraneous components removed.
  • U86 & U87 (78M05) regulators blown, replaced with 7805s.
  • T452 (BC338/16) blown, replaced with TR24.
  • One front panel incandescent lamp replaced.
  • One front panel LED replaced.

Date:1989 Summer
Procedure: Installed in Datsun 710.

Date:1990 Fall
Procedure: Removed from Datsun. Used in basement workshop.

Date:1997 Fall
Procedure: Installed in Honda.

Date:1999 May
Procedure: AM receiver problem. T251 faulty perhaps due to static. Two cracks in PC board traces (390K resistor to T251-G1 connection open, input clamp diode cathode to ground connection open).
T253 moved to T251, T253 replaced with 40673. T253 voltages after replacement: drain=2.9V, source=1.8V.

Date:2007 Oct
Procedure: Schematic redrawn from manufacturer original. Microprocessor inferred to be F3870 family.

Date:2015 Oct
Procedure: No reception on AM. U451 (TDA1046) AM receiver has odd voltages on pins, notably pin 16 which should be an internally regulated +3.3V is +7.25V. Voltages on 3 MOSFETS in AM section look quite sensible. U451 removed. Voltages on empty pins are sensible. Powering up the IC with 8V supply shows 7.3V on pin 16. Internal regulator in IC appears to have failed. Need a TDA1046.

Date:2015 Oct
Procedure: Volume level will not go below approximately half. ULAUT is 2.16V, rather low. LAUT signal is inverse control so the low ULAUT is inhibiting the volume from going down. T453 found to have CE conductivity, replaced with 2N3904. Fixed.

Date:2015 Nov
Procedure: Sharp, loud pops from speakers at seemingly random intervals but rate of occurrence changes with station. Rate increases if bass control is increased. Scope shows bursts of tens-of-KHz oscillations emanating from U451 (TCA5500) L/R outputs. UKLAN (voltage for tone control DA converters) is over +11V when it should be nearer to +5V. T451 found to have CE conductivity, replaced with 2N3904. Fixed.

Measurements taken for ULAUT, UKLAN, etc.

Date:2016 Jan
Procedure: Replacement TDA1046 (U451) installed. Fully functional.

Date:2016 Jan
Procedure: Supply current measurements performed, supply voltage = 13.5V.
Accessory off: 13 mA
Accessory on: 92 mA
Turned on, volume at minimum: 490 mA


  Unit Log
Becker Grand Prix 612 		bhilpert
2015 Nov