Replacement for MM5740AAE/N ?

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Joined: Oct 28 2021 - 09:48
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Replacement for MM5740AAE/N ?


I checked the availability in LittleDiode (the site suggested in the Mike Willegal instructions) and they quoted me this chip at a whooping 105 GBP (> 140 USD)

Is there any cheaper replacement?

I'm willing to try to make this keyboard, but the chip seems a blocking factor.


Last seen: 3 weeks 5 days ago
Joined: Jul 5 2018 - 09:44
Posts: 2587
The guy who makes this

The guy who makes this replacement for the AY-5-3600-PRO might be able to make one.


It doesn't look anything like the real chip, but maybe if you left off the jumpers a cover could be make that looked more like a plastic chip package.


Last seen: 19 hours 38 min ago
Joined: Apr 1 2020 - 16:46
Posts: 885
How to replace elusive keyboard controllers.

In post #1, pfuentes69 wrote:


"They quoted me this chip at a whooping 105 GBP (> 140 USD)"


Uncle Bernie chimes in:


The Apple-1 world seems to be plagued by usurious prices everywhere. I could tell you stories ! Even 3 years ago when I bought the ICs to make 100 Apple-1,  and sunk about $27k into the project, the rarer ones where not exactly cheap anymore (so I paid too much), but now, we see $150-$200 for one lousy Signetics 2513N (20 x what it should cost, maximum), and the price of the 2504/1404 shift registers and the 2519 also went through the roof. So we have to use drop-in substitute ICs, which exist for the 2513N, and the  2504/1404, but not for the 2519. The 2519 was only made by Signetics. But trust me, I have hatched a plan to destroy the usurers and "the spice will flow" (cit. "Dune", by Frank Herbert). There will be more of my kits, many more. And there will be plenty of 2519B, much more than you can ever imagine. All all at a good and fair price !


But for the keyboard controller, we are out of luck. However, there are alternatives, as post #2 above pointed out. We can always make small daughter cards to substitute elusive or usuriously priced  ICs.

The arcade machine crowd did that for many decades. And it works !


In lieu of substituting LSI keyboard controller ICs with similar ones which then also would become too expensive, there are many alternatives:


1) for just building and testing an Apple-1 with my kits, you need no keyboard, you just need the "gimmick switch" for CLR SCREEN and RESET

2) if you have an old DOS based computer, you can build my keyboard emulator cable. All you need is the connectors, some flat band cable, and a NPN BJT.

3) there is a Russian guy on Ebay who sells keyboard converters which directly plug into the Apple-1 keyboard socket

4) we could roll our own TTL based keyboard controller


The last point was inspired when I had to repair a few faulty keys on my Apple-II clone which I use as a test bed for things to come (I try to write my software such that it runs both on the Apple-1 and the Apple II and can be read from the same AIFF file via the cassette interface).


Much to my surprise, I did not find any LSI keyboard controller chip. It seems that even back in the early 1980s, when this clone was built in Taiwan, keyboard controller chips either were scarce or deemed to be too expensive (note this is the same situation we are in now, 40 years later). So the crafty Taiwanese copycats designed their own TTL and EPROM based keyboard controller. Here are the pictures:



Two closeups:







As you can see, the amout of TTLs needed is not prohibitive. If we could modify the existing keyboard Gerbers to incorporate this type of TTL based keyboard controller, then these nasty usurers could never extort us again. They can FOAD (not the nicest American acronym, only the Brits have much worse curses).


These were my suggestions to terminate the keyboard controller IC usurers once and for all.


Comments invited !

Last seen: 3 months 3 weeks ago
Joined: Oct 28 2021 - 09:48
Posts: 28
Thanks softwarejanitor and

Thanks softwarejanitor and UncleBernie


I contacted Joe and I'm asking him about the possibility to have a replacement for this particular encoder.


I also saw in this post ( a keyboard made by AppleMicha that shows a modern replacement, but so far I couldn't know more about it, despite having asked in the forum and directly. Hopefully he'll be around and can give more info.


I think nowadays should be easy to make something based on Arduino-like microcontrollers, which I guess this is the option taken by these replacements. 

Last seen: 3 months 3 weeks ago
Joined: Oct 28 2021 - 09:48
Posts: 28
I think I found it

I found this:


I think this is the same one shown in the post I mentioned above. Unfortunately they don't ship to Switzerland


BTW. I contacted Joe and he could be interested on building this replacement, but he's too busy now, so not happening anytime soon I think.

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