Macintosh Classic compatible EPROM

[karrots]

What EPROM parts are compatible with the Macintosh Classic logic board?

 

[bibilit]

Don’t know really but probably easier to find a Maxell board for next to nothing and remove the original unit. 

 

[karrots]

Via the schematic, I found the original chip is a TC534200. I was able to find this cross reference for compatible EPROM chips. Unfortunately, they are all out of production but there seems to be a fairly decent stock on ebay/Aliexpress. Unfortunately, it's not pin-compatible with the 27C4096 as that is still available in the OTP form from Digikey.

(4M) 256k x 16 / 512k x 8 mask rom           AM27C400 / MX27C4100


     TC534200,
     MB834200,
     HN62404,HN62424
     23C4000  <pin 12 OE,OE/ programmable>

A17  1 +-v-+ 40  A8                     A17  1 +-v-+ 40  A8
A7   2 |   | 39  A9                     A7   2 |   | 39  A9
A6   3 |   | 38  A10                    A6   3 |   | 38  A10
A5   4 |   | 37  A11                    A5   4 |   | 37  A11
A4   5 |   | 36  A12                    A4   5 |   | 36  A12
A3   6 |   | 35  A13                    A3   6 |   | 35  A13
A2   7 |   | 34  A14                    A2   7 |   | 34  A14
A1   8 |   | 33  A15                    A1   8 |   | 33  A15
A0   9 |   | 32  A16                    A0   9 |   | 32  A16
CE/ 10 |   | 31  BYTE/             PGM/,CE/ 10 |   | 31  BYTE/,Vpp
GND 11 |   | 30  GND                    GND 11 |   | 30  GND
OE/ 12 |   | 29  D15 / A1               OE/ 12 |   | 29  D15 / A1
D0  13 |   | 28  D7                     D0  13 |   | 28  D7
D8  14 |   | 27  D14                    D8  14 |   | 27  D14
D1  15 |   | 26  D6                     D1  15 |   | 26  D6
D9  16 |   | 25  D13                    D9  16 |   | 25  D13
D2  17 |   | 24  D5                     D2  17 |   | 24  D5
D10 18 |   | 23  D12                    D10 18 |   | 23  D12
D3  19 |   | 22  D4                     D3  19 |   | 22  D4
D11 20 +---+ 21  Vdd                    D11 20 +---+ 21  Vdd

 

[karrots]

If anyone else ends up using AM27C400 EPROMs you'll need the following information.

The AM27C400 is not compatible with the TL866 family chip reader/writer. Find an adapter board at the GitHub link below. There are many out there prebuilt to buy from the arcade community.

https://github.com/mafe72/27c160-tl866-adapter