Mac Plus keyboard cable

No, it is not the same. In order to avoid damage to any circuits, I recommend an Internet search for details about the correct wiring/pinouts. See also:

http://support.apple.com/kb/TA29935

Jan

Jan,

I took a look at the support article kb/TA29935. As I read it, it does not indicate the pin position for both ends which means that the article, in and of itself, does not rule out the use of standard flat phone wiire.

I dug a keyboard and cable out of storage. If SG1776 is still following this post, I will test the cable. The cable is flat phone cable and not twisted pair. A simple concontinuity tester should let me confirm the wire positions. If positions 1-2-3-4 on one end connect to positions 1-2-3-4 on the other end, and a four pin phone wire does the same, without trading positions, then he should be OK. The second option would be for him to build his own phone cable with a crimping tool.

Ji~m

Hi Jim,

According to a section 9.1.3 of the Classic Mac Repair Notes by Thomas H. Lee, the connections are reversed on one end. That means that it should be possible to modify a cable, but you would have to know exactly how to do it in order to avoid damages.

Jan

In Washington state, Seattle is the best location for recyclers who care about saving older Mac components. RE-PC sets aside older Mac and Apple items for public resale. We closed down the last "used mac only" store in Spokane - eastern WA in 1999. We have leftovers that we use for youth educational projects. We can test, we are not set up for mail order sales. What is the largest city near you? Maybe we know a contact.''

Ji~m

I recall a PBS episode of 'This Old House' that took place in your neck of the woods. There was a big push for recycling and salvage. I can not imagine not having some shop in town that has set aside older gear for the die hards. Push come to shove, we could mail a cable off to you. Making your own cable would be easier. We will verify the pin outs and post back.

http://www.bmac.org/contacts.html shows a list of individuals who should know who would know or have resources.

_"W. 'Ian' Blanton has been involved with the Macintosh from the time in 1988, when he kicked out the power-plug from his roommates brand new Mac II series and thought he killed it, to being network admin for an entire Air Force base full of macs. He currently works for Tech Superpowers as the Director of Onsite Consulting, where he continues to hone his razor-like Mac skills. If you're into torment, you can read his Weblog._Email Ian

Also, Grant is from Boston and might know some resources.

Hi,

>Is everyone agreed that phone cable needs modification?

If I place the two plugs of a Macintosh Plus keyboard cable next to each other (side by side) on a table, both pointing in the same direction, with both tabs up, the wires are arranged as follows:

yellow-green-red-black yellow-green-red-black

Placing the two plugs of a handset cable from one Swedish telephone the same way, results in the following:

yellow-green-red-black black-red-green-yellow

Both cables use the same type of plug (4P4C).

As shown by this simple comparison, at least these two cables are different.

See also the 'Data port' text in this article:

http://en.wikipedia.org/wiki/4P4C#4P4C

In the case of the Swedish telephone handset cable above, it appears as if turning one of the two plugs 180 degrees (using a crimping tool) would result in a cable that could be used for a keyboard. However, this is not a recommendation. Proceed at your own risk if you decide to carry on with any experimental modifications. I have not tested any modified cables.

You should check whether randomly chosen telephone handset cables in your country have the same wiring/colours as the one I examined.

Jim may also want to verify the wiring and colours with another Macintosh Plus keyboard cable.

Jan

Jan,

You are absolutely right. The pin position and color are as you said with one clairification. Yellow-green-red-black is reading right to left with the metal contacts facing up. What matters most is that the wire in position one - reading right to left or left to right - is identical for both ends. Phones wires are reversed.

As for the quality of phone cable used, the flat lead wire is fairly universal. I would not be afraid to build my own cable.

Once twisted pair was introduced for high speed transmission, ie. cat 5 cable, wire grades became more important.

A quick review of phone history might be in order. Rotary Pulse dialed phones worked with pairs of wires. Red/Green were the inner pair and Black and yellow were the outer pair. Any pair of wires would work. With the advent of touch tone phones, polarity mattered. With the wrong polarity of wires, dialing a touch tone resulted in a 'thud' sound and not distinctive tones. What did not matter is whether you used the inner pair or outer pair.

Ji`~m

Happy New Year. You celebrated long before we did!

Jim,

Happy New Year to you, too!

Via reference 6. in the Wikipedia article above, I found the following web page, which also verifies the keyboard cable wiring and colours:

http://blog.syrinxsystems.co.uk/mac-plus-keyboard-cable/#more-172

As an experiment, I am going to buy some 4P4C plugs and then using a crimping tool

a) modify a coiled telephone handset cord (cutting off one of the plugs, replacing it with a new one turned 180 degrees)

and/or

b) build a completely new keyboard cable (standard 4-lead cable, two new plugs).

The cable(s) can then be tested with a Macintosh Plus. Providing (of course) that the correct wiring is used, it should be OK.

Jan

A new keyboard cable was built using a low-cost crimping tool. After a test with a Macintosh Plus, I can now confirm that everything works well.

A standard (flat) 4-lead phone cable and two 4P4C modular plugs were used. The plastic tool in question had a small adapter piece, needed to correctly position the narrow 4P4C plug.

As indicated earlier, for this keyboard cable, the wires/colours are identical in both plugs. For example, if one holds the two plugs side by side (upright, with the cable openings down) while looking at the locking tabs, the wire colours are:

yellow green red black yellow green red black

Jan

Hi,

A "real" keyboard cable for a Macintosh Plus appears to be made from a (coiled) phone-style flat cable and standard-looking 4P4C plugs, so I do not think that a modified cable as such would differ in any significant way.

However, it is extremely important to connect the wires correctly when building a custom cable. Otherwise, there is a substantial risk of reversed polarity, which could destroy the computer and/or the keyboard. For more information, see the document (web search) mentioned in my second message and the page (link) mentioned in my fourth message. Do not use a normal ready-made telephone/handset cable (with plugs) in connection with a Macintosh Plus.

Also, pay special attention to the crimping quality in order to avoid unreliable connections and short-circuits.

You can probably find a simple crimping tool (that can handle 4P4C, in addition to the broader modular plugs) for around USD 20.

Jan

The cable I made is about 1 metre. It is a plain flat cable, not coiled. A brief test with a Macintosh Plus did not reveal any difficulties. All keys worked as they should. Sorry, I do not know anything about a maximum cable length or distorted signals.

It is not always easy to locate a Macintosh Plus keyboard cable (you may want to search the Internet for one). That is why a home-built alternative could be of interest.

Yes, you would need 4P4C plugs (see the Wikipedia article above). I bought a set of 10 pcs for approx. USD 2 here in Sweden. Since the flat cable I used for the test did not have any plugs from the beginning, I did not have to remove anything. If you start the modification from a ready-made coiled handset cable instead, you can just remove one of the plugs by cutting the cable. Use the crimping tool to strip the outer cable layer (a number of millimetres, determined by the tool). Insert the four wires into the plug (note the correct position). Place the plug in the tool (if applicable, use a supplied adapter for 4P4C) and carry out the crimping operation. Do not forget to carefully verify the wire colours (see the earlier messages) before an attempt is made to connect the finished cable to the Macintosh computer and its keyboard.

Once again, carry out the work at your own risk. If in doubt, it may be better to look for an original keyboard cable.

Jan