Re: Where do I get a POWER OK for Widget?

Am Freitag, 30. März 2018 16:47:13 UTC+2 schrieb Tom Stepleton:
>
>
> On my working Widget, the Power OK pin was pulled up to +5V as James
> suspected. On my broken Widget, however, this did not happen. There's +5V
> on the other side of R1, so something else must be pulling it low. There is
> not much circuit there to do that, though. Pin 2 of U11 is high; pin 3 is
> low; no surprises there. This result obtains regardless of whether the
> controller is plugged into the rest of the Widget.
>
> So, I'll need to figure out what's pulling this line low. It gives me hope
> that this drive can be resurrected---maybe this is the only problem.
> Happily, I was able to use my UsbWidEx to test the Widget's servo directly:
> the drive spins up (with much groaning after 20 years of being idle) and
> the servo walks along the disk in the ordinary way. That's pretty good
> news, I should think!
>
>>
POWER_OK is ANDed with /CRES from the Profile connector. Both are /Reset signals for the Controller board which are low-active. That means to get the Controller Z8 working, both /CRES and POWER_OK have to be at high level (which should be ensured by pullup resistors RP7-2 resp. R1). Pulsing one of them low will reset the controller. If any of these pins is stuck low, the Z8 will not start.

In working condition, Pin 8, 9, and 10 of U1C (74LS09) should be high, and the same high level should be visible at pin 6 of Z8 U4E.

If the servo board passes linear and butterfly seek without losing postion at least the moving parts of your drive are in good condition. Next to test would be R/W (swap in a known-good controller board and do some R/W testing at the format recal position, outside user data area) and the controller itself.

Patrick

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