Tony Duell ard at
Sat Dec 9 15:07:39 CST 2006

> On 9 Dec 2006 at 1:19, Tony Duell wrote:
> > No, I was wrong. According to the manual, the 'ready' signal depends on a 
> > clock signal that comes from a special track on one of the platters, 
> > picked up by a fixed head. The basic procedure if the drive won't go 
> > ready is to look at the output of this head's amplifier, if that's 
> > missing/incorrect to troubleshoot or replace the read/write PCB (and if 
> > that doesn't get it back, then the fault is inside the HDA and is not 
> > field repairable). If the output of the clock head amplifier is OK, then 
> > therer's a fault on the control PCB.
> Thanks,  it's enough to get me started.  I'll let you know if I'm 
> unsuccessful.

OK, here are the actual procesdures from the manual : 

Check the DC volages at the control PCB J6 connector (to the read/write PCB)
Pin J : +5V
Pin E : -5V
Pin 22 : +24V
Pin B  : +12V

(If any of those are misisng/incorrect, there's a procedure to check them 
back through the actuator PCB, etc, but I think you can manage that...)

OK, on to the test you need : Drive Not Ready.
It assumes the power voltages are OK, and that the disk is rotating. 

Notes : 

1) Ready indication will appea as a logical 1 on TP28 of the control PCB.
2) Ready will not become active for 1.5 minutes after AC and DC power are 
3) The drive must be selected befroe Ready is available at the interface 

Test 1 : Check clock track amplitude at control PCB TP9 (must be more 
than 1.5V)

Test 1 OK?
No : Replace Read/Wrtie PCB [1]
     Test 1 OK ?
     No : Problem with clock head -- not field repairable
     Yes : go to test 2
Yes : Got to test 2

Test 2 : Check TP5 on control PCB for TTL level 500ns puleses every 2.2us

Test 2 OK ?
No  : Replace control PCB [2]
Yes : go to test 3

Test 3 : Check TP27 on control PCB for TTL level square wave of 70ns 
+/-5ns (14.2MHz)

Test 3 OK ? 
No : Replace control PCB [3]
Yes : go to test 4

Test 4 : Check TP26 of control PCB for a TTL level pulse 1.1us duration 
every 2oms (Index)

Test 4 OK ?
No : Replace control PCB [4]
Yes : Test done

ARD#'s notes
[1] Check circuitry round 6B and 6D on the read/write PCB, these being 
the clock head amplifiers

[2] Check round 2A and 1B(section b) on the control PCB.

[3] This is the output of the phase-lock oscillator. Check Q3, 3D 
(oscillator), 2B, Q1, Q2 (phase detector), etc

[4] Check counter 2E, register 1G, and associated gates


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