I've been looking for a chart that would show comperable modern chip alternatives to chips on the II/II-Plus. I found a similar chart for Commodore systems and a list of chips for the Apple II/II-Plus but have yet to find a modern replacement chart. While new to this granularity of electronics I am learning fast how to read the chip designations, such as the various families of the 74LS chips, etc. But, I am still learning how to know if the modern version of a chips, such as a 74LSxxxxN, etc is truly backwards compatible.
Does anyone have any suggestions or guidance on where to either find a comparison chart. If not, I may start trying to make one by digging throuh the Datasheet of legacy chips and seeing if it looks like modern versions I find will be acceptable. I checked Apple II files on asimov but no luck yet.
Since almost all the logic chips on the motherboard are still available (even though not all are in production any longer) it's really not required.
The three important substitutions that are relevant are:
- the 9334 at F13, which is like a 74LS259
- the 8T97 at H3-5 which can be substituted with a 74LS367
- and the 8304 octal bus transceiver at H11 which can be substituted with a 74LS245 (but the pinout is slightly different so you'd need a socket adapter).
- the NE558 are obsolete and getting hard to find. I don't know of a substitute.
- the 74S86 at B2 is also obsolete, (and could be subbed with a 74LS86 in a pinch but can be unstable, especially with multiple expansion cards).
74S86 are still around if you look.
- he 74166 at A3 is replaceable with a 74LS166 (and both are still avilable if you look).
All the other 74LS logic is petty easy to find at places like Jameco, futurlec and even Mouser and Digikey for some common types. I keep multiple spares of every chip on hand, including the CPU and 2716 EPROMS (you can use them in place of the Apple PROMs with socket adapters) since the prices are still very low.
> I found a similar chart for Commodore systems and a list of chips for the Apple II/II-Plus but have yet to find a modern replacement chart.
The original list is this:
This one will be the most actual. Ask me if there are questions, errors or additional informations ...
There are a couple of things that can be done if one needs to replace the 74S86 or 558.
While repairing my Franklin ACE, I had to validate various circuits. The main oscillator circuit was very far out of spec, and the game port didn't work.
The 74S86 was used (as opposed to other TTL logic family '86) because that was the old-school way of generating a clock from a crystal. Feed the sine wave into an '86 (with one input wired high; also common to use a 74S04) and you'll get a reasonably-50-percent-duty-cycle out of the gate. The '86 has one other gate used, but it doesn't depend on Schottky behavior.
What I ended up doing was whomping up a small circuit board that sits in the socket for the '86. The board replaces the clock output from the '86 with the output from an onboard can oscillator. The 74S86 can then be swapped out for something less rare, and the need for PN4258 goes away as well.
For the 558, there's a drop-in replacement using two 556s here: https://github.com/roybaer/ne558_replacement ... it seems to work okay in my use case.
Isn't this the same 74S86?
So 4116 (16kx1) are readily available. I assume these (Jameco) are aceptable replacements for the Apple II+? One question. Does speed matter?
Jameco, for example, has 4116 at both 150ns and 105ns (linked above).
Are both acceptable?
Yes, DRAM speed matters but as long as you use 200ns or less, it should be ok.
Note the Jameco 105ns Mostek MK4516N-15 RAM Chips have the note:
Unlike the 4116 chips which require three voltage supplies (12V, +5v, -5v), the 4516 chips are a single voltage supply (+5v) chip.
At first glance they appear to be a 16K compatible version of the 4164 newer generation 64k chips.
4116-150 is the acceptable chip, the 4516-105 is not acceptable.
Thanks for the heads up.
Just to be absolutely sure. These are the compatible chips? Correct?
Yes, these are the correct chips.
I need to replace a bad D8.
From everything I have been reading online, here and other places, the desired ROM replacement process is through the Integer ROM cards. I believe there are EPROMS 2716? that can replace the originals with some pin rewire. I have the ROM images, and an EPROM burner. There are several 2716s on sites like Jameco. Which ones are appropriate replacements? Jameco has refurbished EPROMS, UV erasable but 450, 350, 200ns.
What ways have people used successfully? I heard using standard PCB header pins don't work in the sockets or damagee the sockets so I am hesitant to buy replacement ROMS on eBay that aren't originals.
Building a Brain Board might be an option too.
But, I understand the Brain Board can't fix a bad D8.
Oh, and is there a modern replacement for the CPU? Just curious and want to have one on hand.
You can get 2716 chips to work in a II / II+ with a chip socket adapter. It's a little bit involved because you need to invert a couple of signals on the 2716 for it to work in place of the 9316 chips on the board. Use the 200 ns ones.
There are a few caveats. First, 2716 chips are hard to program with the inexpensive chip programmers on eBay and AliExpress. Most vintage 2716 chips need 24 volts on the programming pin to "burn" successbully, and most USB connected programmers can barely squeak out 21 volts. There are a few alternatives but they're expensive.
For 2716 programming work I use a vintage slot card on my II+ that was designed to output the correct programming pin voltage.
For anything else - 2732, 2764, 27256 etc, the USB programmers work fine.
If you're looking to replace a single ROM chip, look here for a compatible replacement: https://www.reactivemicro.com/product/9316a-to-2716-soic-eeprom-adapter/
Expensive, yes, but pretty much guaranteed to work.
If you want to DIY it, look here: http://www.willegal.net/appleii/appleii-integer.htm
It is also possible to use 2732 and 2764 chips in place of the 2716 chips but you will have to double (or quadruple) the code to fill up the empty space on the larger chips.
I've done this before with some success. The same inverting procedures will need to be applied in order to use them in place of the original 9316 chips.
28C16 EEPROMs are an alternative to 2716 too, works with the TL866II+ programmer. Data retention is only 10 years though (at least the Atmel variant). And I don't know how suitable they are for ROM replacements.
Yeah, I think the best solution here is to just buy one from ReactiveMicro.
Thanks for all the info.
Any thoughts on modern CPU replacements or would you recommend the ReactiveMicro ones for that as well?
You can buy brand new 6502 chips from Western Design Center, but you have to do a bit of pin re-assignment to make it work in the IIe. Nothing major, and you'd be getting a brand new CPU that's as reliable as is possible.
The modifications are explained here: https://www.westerndesigncenter.com/wdc/AN-002_W65C02S_Replacements.php
And you can order here: https://www.mouser.ca/ProductDetail/Western-Design-Center-WDC/W65C02S6TPG-14?qs=opBjA1TV903lvWo9AEKH5w==
Or here: https://www.jameco.com/z/W65C02S6TPG-14-Western-Design-Center-MPU-8-Bit-14MHz-65KB-Memory-40-Pin-PDIP_2143638.html