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