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28C64 in 2364 socket (28 pin to 26 pin)
Posted: Sun Apr 08, 2018 10:48 pm
by mrtinb
To fit an 28 pin EEPROM in a 2364 PROM socket needs a conversion circuit.
It's built but not tested.
Design using strip board, here are some pictures. It will only work, because this is a double sided strip board, where every hole is connected top to bottom. Design of bottom side does not show strip board even though it is. It needs to be double sided, as the female sockets is soldered on top, and male socket is soldered on bottom.
It still needs a little cleaning with alcohol to clean out the flux.
Re: 28C64 in 2364 socket (28 pin to 26 pin)
Posted: Sun Apr 08, 2018 11:44 pm
by McKlaud
Nice
I've done something similar for SMD EEPROM chips. See below:
The project is public on OSHPark, there:
https://oshpark.com/shared_projects/ArG7JDff
Re: 28C64 in 2364 socket (28 pin to 26 pin)
Posted: Mon Apr 09, 2018 6:34 am
by Paul
McKlaud wrote: ↑Sun Apr 08, 2018 11:44 pm
Nice
Your little PCB is very nice as well
Re: 28C64 in 2364 socket (28 pin to 26 pin)
Posted: Mon Apr 09, 2018 7:06 am
by mrtinb
Claudius: How do you program the SMD when it is soldered to this PCB? No EEPROM burner recognizes a 24 pin 28C64.
Re: 28C64 in 2364 socket (28 pin to 26 pin)
Posted: Mon Apr 09, 2018 9:02 am
by McKlaud
Burn before soldering.
The space inside the Zeddy's case is very limited. Unfortunately you will not be able to fit your adapter there and close the case.
Re: 28C64 in 2364 socket (28 pin to 26 pin)
Posted: Mon Apr 09, 2018 5:21 pm
by Lardo Boffin
Is is possible to buy a complete one of these anywhere?
My ZX81 total rebuild (which I will finish in the next few months
) only has the case, ROM and PCB as original parts. Everything else is either new or ‘new old stock’. It would be good to also replace the ROM with something like this so it is as new is it is possible to be!
Re: 28C64 in 2364 socket (28 pin to 26 pin)
Posted: Sat Apr 14, 2018 12:40 pm
by mrtinb
mrtinb wrote: ↑Sun Apr 08, 2018 10:48 pm
To fit an 28 pin EEPROM in a 2364 PROM socket needs a conversion circuit.
It's built but not tested.
I couldn’t get it to work. But then I found that the EEPROM contained 00h’s every time it had been tested.
Then I realized that /WE should be tied to 5V and not floating. The two pins were next to each other, so a huge pile of solder fixed the circuit.
Re: 28C64 in 2364 socket (28 pin to 26 pin)
Posted: Mon May 14, 2018 12:28 am
by McKlaud
Hi Martin,
Have you managed to squeeze your board inside the Zeddy case? I went to the SMD route and still the board a bit too fhigh. I should buy some flip-pins and try them.
Re: 28C64 in 2364 socket (28 pin to 26 pin)
Posted: Mon May 14, 2018 4:50 am
by daybyter
Could you sand the black plastic spacers a bit shorter and then cut the pins by 1 or 2 millimeter? With a dremel and diamond disc maybe?
Re: 28C64 in 2364 socket (28 pin to 26 pin)
Posted: Mon May 14, 2018 6:37 am
by Paul
You could put the EEproms on the bottom side.