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

Hi all,

I extracted U11 from my broken Widget's controller board and found on a breadboard that its first AND gate (the one that the POWER_OK symbol deals with) was broken. After replacing it, the Widget works again---as well as can be expected at least for a drive that hasn't really run for a couple of decades. I'm now downloading its contents with my UsbWidEx. Occasionally the spindle bearing gives off a frightful groan, but I can't really blame it.

I've seen two posts on the 68kmla forums say that you need to supply +5V on the POWER_OK pin to run a Widget on an external drive. This makes me wonder whether U11 is prone to fail now and then, and whether powering POWER_OK might work around some kinds of U11 failures. I don't know how plausible that is, but I did put my replacement U11 in a socket, just in case I might need to do the operation again someday.

--Tom

On Saturday, March 31, 2018 at 2:08:49 PM UTC+1, PSchaefer wrote:
>
> 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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