ECA 008 - speaker noise

ECA 008 - Speaker Noise

Continuous speaker noise on 8580 mod 111 and mod 311 (ECA008)


To provide instructions for identifying and replacing 8580 model 111 or 311 system planar boards that cause erratic speaker operation or noise when a Math coprocessor is installed.

Machines Affected
80-111 serial # below 6019000 see physical check!
80-311 serial # below 6502022 see physical check!

  1.  Suspected planar boards (FRU P/N 90X7390), can be identified  by checking the part number of the planars and of the PAL in  location U26. Good planar boards can be identified by P/N  15F7979, 15F7982 and 15F7985. These however must have U26 part  P/N 15F7988.
  2.  Down level P/N are 15F6603, 15F6606 and 15F6727.  these will have U26 with a P/N 90X8011.
  3.  Check for the installation of the 80387 Math Coprocessor.  The location of the Math Coprocessor can be found in the PS/2  model 80 quick reference manual on page 39 or the HMR on p3.10.  If a Coprocessor is installed and the planar is identified as  listed above,replace the planar board as instructed in the  detail section of this ECA:.
  4.  If any other P/N than those listed above or there  is no Coprocessor installed, no further action is required.

The 8580 speaker makes a crackling noise and/or short beeps. The worse case condition is the speaker turns on continuously and cannot be reset. Only 8580 models 111 and 311 with an 80387 Math Coprocessor installed are affected.

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