5-JAN-2010It’s time to fix my 9-track tape drive, a Cipher 880. The Cipher 880 9-track tape drive installed on the DSVAX III would usually work up to the point of an “init”, but a fault would always develo Subsequently, testing the arm movement found no problem (service aid 24 found normal voltages). Thus I decided to open up the drive and check what gives. Checking the huge PCB, I found Running the tape drive open, another problem suddenly appeared – the vacuum motor was constantly “on”. Running diagnostic test No. 34 and pressing the LOAD button did not manage to switch it off either. I have tracked the problem to a faulty chip, U17P (A 7438 hex schmitt trigger inverter).
The offending IC 7-JAN-2010 U17P (7414 Hex Schmitt Trigger) Removal and Replacement
After replacing the offending 7414, the problem was solved – the suction motor is again under control. Now it is time to dig in and solve that “error code 17”. 8-JAN-2010Test Point Waveforms, Compliance Arm Adjustment TP56 looks OK, TP59 looks a bit odd – perhaps U20N (4136 op amp) is faulty ? Before attempting a replacement – I tried re-adjusting the compliance arm tension spring, releasing the mounting screw and changing the spring load force (the mounting screw and bracket are the ones marked with blue dye in the photo). But it did not help – code 17 problem persisted, even with spring tension increased or decreased.
10-JAN-2010U20N Replacement It is time to replace U20N. I chopped it away, removed
Testing the tape drive reveals that indeed the 4136 was faulty. Now the tape spins again. |
Status: (2017): Can mount a tape, see its label under VMS. But any attempt to read from it quickly aborts with various read errors. Need to tune the read threshold using test aid 21.