[Coco] calling all MM/1 owners

[Joel Ewy]

Bob Devries wrote:
> Joel, as far as I know, the termination resistors have a power and a
> ground pin at opposite ends with a number of pairs of 220 and 330 ohm
> resistors strung between them. The centre point of these pairs is
> connected to the SCSI bus data/control lines. Yes, having them
> backwards would make some difference, but how much? Certainly it
> appears that it's not enough to stop the SCSI cold.
>
Sounds like you need to do some rework on your I/O board.  :-(  I'd
offer to send you some parts but it probably doesn't make sense to ship
to Australia from central Kansas.  (There ought to be some kind of
tornado-powered Oz to Oz express wormhole...)  I still have MM/1 I/O
board parts, though I have it in the back of my mind that the
terminators for the SCSI interface may have changed to a different
package between the board you have and the ones I was going to produce. 
And I have a rail of unused DS1287As -- brand new in about 1994.

JCE
> -- 
> Regards, Bob Devries, Dalby, Queensland, Australia
>
> Isaiah 50:4 The sovereign Lord has given me
> the capacity to be his spokesman,
> so that I know how to help the weary.
>
> website: http://www.home.gil.com.au/~bdevasl
> my blog: http://bdevries.invigorated.org/
>
> ----- Original Message ----- From: "Joel Ewy" <jcewy at swbell.net>
> To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
> Sent: Friday, January 25, 2008 1:54 PM
> Subject: Re: [Coco] calling all MM/1 owners
>
>
>> Bob Devries wrote:
>>> I just removed the I/O board from the MM/1 to more closely examine the
>>> RTC.
>>>
>>> I found that one of the termination resistors for the SCSI bus is
>>> oriented the opposite way to the other two. RN5, the middle one is
>>> different. Now I'm wondering what effect this will have on the working
>>> of the SCSI bus? Could this be my problem?
>>>
>>> Joel, the termination resistor's 'notch' or 'dot' end should be in the
>>> solder pad that's square, am I correct?
>>>
>> Yeah, that's right.  I think that's the common lead for the resistors.
>> Resistors themselves aren't directional.  Does it make a difference
>> because of the way they're assembled in an array?
>>
>> JCE
>>> -- 
>>> Regards, Bob Devries, Dalby, Queensland, Australia
>>>
>>> Isaiah 50:4 The sovereign Lord has given me
>>> the capacity to be his spokesman,
>>> so that I know how to help the weary.
>>>
>>> website: http://www.home.gil.com.au/~bdevasl
>>> my blog: http://bdevries.invigorated.org/
>>>
>>> ----- Original Message ----- From: "Dave R in Illinois"
>>> <lazyhand at sbcglobal.net>
>>> To: <coco at maltedmedia.com>
>>> Sent: Thursday, January 24, 2008 12:03 PM
>>> Subject: [Coco] calling all MM/1 owners
>>>
>>>
>>>> Have you checked to make sure the drive / cable is properly
>>>> terminated? I've
>>>> seen corroded pins on terminators do strange things to raid arrays. I
>>>> never
>>>> owned a mm1 so I am not sure if there even is one, I would assume
>>>> there
>>>> would be.
>>>>
>>>>
>>>>
>>>> -Dave
>>>>
>>>>
>>>>
>>>> ______________________________________________________
>>>>
>>>>
>>>>
>>>> I have a small problem with my MM/1, and I'm wondering if there was
>>>> ever a
>>>> fix for it?
>>>>
>>>> When I power it up, the computer goes through its procedure to try to
>>>> boot
>>>> from the floppy, and then from the SCSI hard disc. It *always* locks
>>>> up the
>>>> SCSI bus at that point, and pressing reset does not unlock it. I
>>>> need to
>>>> cycle the power to unlock it. It then usually fires up correctly, but
>>>> not
>>>> always.
>>>>
>>>> My MM/1 is a 3MB with the expansion board. It has a 170MB Quantum SCSI
>>>> drive. The drive itself initialises properly (at least, it makes
>>>> all the
>>>> right noises).
>>>>
>>>> Comments anyone?
>>>> -- 
>>>> Regards, Bob Devries, Dalby, Queensland, Australia
>>>>
>>>> Isaiah 50:4 The sovereign Lord has given me
>>>> the capacity to be his spokesman,
>>>> so that I know how to help the weary.
>>>>
>>>>
>>>> -- 
>>>> Coco mailing list
>>>> Coco at maltedmedia.com
>>>> http://five.pairlist.net/mailman/listinfo/coco
>>>
>>>
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>>
>>
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