TS1000 white screen but no K

[1024MAK]

Also, the supplier I linked to for this: “ROM EL-2364 FLASH EPROM Chips (replacement for 2364 ROM)”. He can arrange to program it for you if you wish. He does charge extra for this service, check with him for the cost.

Mark

[junkman]

OK I checked both busses between GRD and vcc. No shorts detected. Also between each other. No shorts detected.
I also checked for shorts on the ram pack busses.

I then lifted the /HALT pin on the Z80 and scoped it. Nice clean high coming out of the CPU. It never drops as long as the machine has power.

Everything on the board seems to be marching to the beat which you can clearly see on ROM pin 13 https://www.youtube.com/watch?v=NlXft5Q3ex8&

Thank you for those links to the ROM sources. I have access to a cheap chinese (TL866II) programmer. I know it can't program the old style eproms but I am wondering if it can at least read them?

I may try pulling this ROM and seeing if I can get the data off it before rolling the dice on ordering parts internationally.

[junkman]

I think I found a USA source for the 2364 to 2764 adapter https://store.go4retro.com/2364-adapter/
Now I just need to figure out what is 2764 compatible that the cheap programer can program. It can only do 18 volts and a real 2764 seems to need 21+

[Moggy]

I think I found a USA source for the 2364 to 2764 adapter https://store.go4retro.com/2364-adapter/
Now I just need to figure out what is 2764 compatible that the cheap programer can program. It can only do 18 volts and a real 2764 seems to need 21+

I use 2764's quite a lot in my zeddies and as you say the older devices require21v to program, however if you come across the later version of that chip marked 27c64 then it only requires 12v to program.

You may want to consider which ROM image to use as there have been a few improved ROM images over time the latest and in my opinion the best is the double speed BASIC ROM found here....

https://www.sinclairzxworld.com/viewtop ... f=5&t=2986

It really does speed up BASIC in a lot of applications.

[junkman]

Thank you for the link to zsolt's rom. I was just going to burn a stock one in but this one looks interesting

Good to know on the 27c64's. I ended up ordering a pair of M27C64A-10F1. I don't have a UV eraser so hopefully they show up blank or I am going to need about 2 weeks of sunny days here

[junkman]

Well I got the programmer and managed to read something from the ROM. I have it set for 27c64.
I attached a zip file (firstread) with the BIN file I got off the ROM.

EDIT
It seems like it has 8 bytes different with the "standard version 2 improved rom".

EDIT 2
I put that rom image in to an emulator and it seems to be stuck in a loop at about the same rhythm I am seeing on the oscilloscope.
https://youtu.be/KUkJbVnkFNk
Hopefully I am on the right path.

[mrtinb]

I've had success with AT28C64 EEPROMs that can be programmed with an Arduino. Then I made an adaptor board with stripboard.

[junkman]

I've had success with AT28C64 EEPROMs that can be programmed with an Arduino. Then I made an adaptor board with stripboard.

Neat! I see the pinout looks like the same as 27c64 eprom. Is it a drop in replacement? It would be nice to have an EEPROM replacement for the uv EPROMS to go in the adapter I ordered

[mrtinb]

I don’t know.

I just looked at the data sheet for both of them, and created my own adapter.

[junkman]

Ok I looked in to the AT28Cxx some more. I found an AT28c256 chip and tried wireing it up with jumpers off a breadboard. No joy. I tried repeating the ZX81 rom code 4 times to fill the chip. Different combo's on the A13/A14 pins of the EEPROM set hi/lo would make a grey screen or a black block rotating around.