error in Apple M0110A wiki

[Herb Johnson]

Pardon me, if this forum is not the correct forum for possible errors in a wiki entry. I'm new to participating.

The page "Apple M0110A" has this statement:

The protocol is an extended version of the one for the M0110, but the leads on the wire are not crossed, so a standard telephone cord can be used as a replacement or extension.

End quote. It's referring to the coiled cable between the Mac and this keyboard model. The M0110 was sold with the Mac 128K and 512K, the M01101A sold with the 512K and Mac Plus.

The error is twofold. One, the two Apple model's coiled cables are in fact interchangable. I've serviced these Mac models for decades and never found a difference among their cables, other than color (some are grey). So: all Mac keyboards for the models above use the same Apple keyboard cable.

Two, there's historic warnings that a coiled land-line telephone cable will fit - the connectors are RJ-11's - but the telephone cable is wired differently. Use of a telephone cable will result in *reversed 5V DC* to the keyboard, which often will cook the keyboard microcontroller. Now - I've not confirmed this reversed connection, I've simply avoided use of telephone cables. If there is sufficient interest, I can test known Apple and telephone cables on a Mac Plus and use of a voltmeter and ohmmeter (I won't fry a keyboard).

But the essential issues are 1) no change in Apple coiled cables across these models; 2) don't use telephone cables. I'll look for responses and comments. Thanks.

Herb Johnson

[Slom]

Pardon me, if this forum is not the correct forum for possible errors in a wiki entry. I'm new to participating.

You can change the information in the wiki yourself. The login button is in the top right corner and the username/password is the same as for the deskthority forum.

Otherwise, this forum should be correct ... and as I have no clue about apple keyboards I'll show myself out

[Daniel Beardsmore]

Hello Herb, good to see you here.

My principle personally is that claims on the wiki should be backed up by either a reference, or photos or PDFs. Having all the information self-contained (via uploaded media) is preferable for ease of use, but references are fine if that's not presently possible.

In this case, the claim is not backed up, so one cannot either affirm or refute it based on the page contents. (This is precisely the problem I have with unreferenced claims — no-one's any the wiser as they can't verify for themselves.)

Personally I have nothing to test with, my oldest Mac now is a Classic :)

[snuci]

You don't mess with Herb

References added on the Apple M0110A wiki page and cleaned up the confusion. I have interchanged M0110 and M0110As dozens of times myself between Mac 128k, 512k and Mac Pluses without any issues.

I have never tried a phone cord because of the warnings but Daniel Kottke cleared it up in a quote on the Mac GUI reference stating: "The Mac's cord has heavier gauge wire to prevent drops in voltage that don't stop you from understanding phone conversations but can interfere with the accuracy of the digital signals the Mac uses. If you replace the Mac's cord with a telephone handset cord, it doesn't damage the keyboard's microprocessor, but it won't work." The author of the page still didn't believe him so he tried it and Daniel was right. He should be; he co-designed the keyboard

Thanks for chiming in Herb.

[tactica]

Next stop is to provide schematics and some concise instructions in the article rather than pointing to external references that eventually may break... or just for those in a hurry

[Herb Johnson]

Thanks and compliments to "snuci" for updating the Wiki M0110A Web page. I likewise found the Apple Tech Note as now referenced. The likely definitive references, are in the "Inside Apple" series which describe the hardware interfaces by product. As time permits I may edit those into the page. But the essential edit has been done - the keyboard interface for Mac 128K, 512K, 512KE, Plus are the same, the Apple cable is "straight thru" use that. A phone cable is not so don't use that. This is not hard. Avoiding damage is an additional consideration.

I'd further mention: there's 5 volts and ground on the interface and thus there ARE risks of damage if a cable is miswired. Such damage has been reported but that's not authoritative. Consequences of misplaced grounds and DC power on 1980's digital logic are nonetheless well-established as a risk of damage.

Put another way: I can't "prove a negative", it's entirely possible one could "try it" and on some "try" you'd not get damage at that event. Arguing further, in my opinion, becomes an argument of decreasing returns: my credentials versus yours, documenting failure modes, accumulating evidence of experience, etc. etc. This is a lot of work, about the wrong cable.

Herb Johnson
retrotechnology.com