Tektronix 2465A

[stfjohn]

Hi everyone. My Tek 2465A suddenly showed the following problem: at power up the message "TEST 04 fail 13 <017F> appears. I tried to replace the microprocessor, the ROM and also the RAM (also the battery), but nothing changes. By moving pin 501 to "CAL", and trying to calibrate the device, the procedure does not work: simply the device checks the various tests, reconfirming the FAIL to test No. 04! Can anyone help me please? Thanks.