EPROM for 4K ZX80 ROM?

Discussions about Sinclair ZX80 and ZX81 Hardware
RetroByte
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Joined: Mon Mar 12, 2018 1:33 pm

EPROM for 4K ZX80 ROM?

Post by RetroByte »

I bought 5x TMS2532A but only 2 would program.

Is there a better option? I have a TL866CS programmer and made an adaptor for these TMS2532A.
Moggy
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Joined: Wed Jun 18, 2008 2:00 pm

Re: EPROM for 4K ZX80 ROM?

Post by Moggy »

I think you might just have been lucky to program the two out of the five as in my experience modern programmers struggle with the 21/25v programming voltage.

A 2732 can be used but then the same problem applies however and like the 2532 a slight mod is required for it to work but there is a modern chip that can be supplied programmed (for a small cost) from Sell My Retro.

https://www.sellmyretro.com/offer/detai ... om%29-2339

EDIT.

Both EPROMs and required mod.
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Last edited by Moggy on Mon Feb 15, 2021 2:03 pm, edited 2 times in total.
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1024MAK
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Re: EPROM for 4K ZX80 ROM?

Post by 1024MAK »

Better, err, probably not. Alternative, maybe...

It’s possible to use larger capacity 27 series EPROMs that only need a 12.5V or a 21V programming voltage or 28C64 EEPROM chips. These do however require the bending out of some of the pins, as the pin-outs are different to that of the ROM chip that Sinclair used. The most obvious thing is that the existing ROM is a 24 pin DIL/DIP package and the 27C64 or 28C64 come in a 28 pin DIL/DIP package, so pins 1, 2, 27 and 28 hang out over the top end of the socket.

TMS2532A EPROMs are rather old now. As they get older, or if they have been erased a lot, programming takes longer and becomes less reliable. Also the official programming voltage is 25V at 30mA. The inexpensive modern programmers are not normally able to maintain this supply during programming.

Do your ‘failed’ EPROMs verify in the programmer?

Mark
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RetroByte
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Re: EPROM for 4K ZX80 ROM?

Post by RetroByte »

1024MAK wrote: Mon Feb 15, 2021 1:54 pm

Do your ‘failed’ EPROMs verify in the programmer?

Mark
Yes, they read OK, all FF's
RetroByte
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Re: EPROM for 4K ZX80 ROM?

Post by RetroByte »

I don't think I have a 30v PSU, but what do you think to this? https://www.youtube.com/watch?v=F9ADB7ImSwc
Moggy
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Re: EPROM for 4K ZX80 ROM?

Post by Moggy »

I would say then the programming voltage isn't up to par. where does this programmer get its supply voltage from and is it possible to use an external programming supply?

If so three 9v batteries wired in series I find is more than adequate when I program EPROMs with no programming failures yet apart from obviously duff ones.
RetroByte
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Re: EPROM for 4K ZX80 ROM?

Post by RetroByte »

Moggy wrote: Mon Feb 15, 2021 2:07 pm I would say then the programming voltage isn't up to par. where does this programmer get its supply voltage from and is it possible to use an external programming supply?

If so three 9v batteries wired in series I find is more than adequate when I program EPROMs with no programming failures yet apart from obviously duff ones.
The programmer must up the voltage from the USB's 5v supply. I use a split USB cable to add extra amps.
The programmer has no socket for extra power.

I was thing about 3x 9v batteries, so it's nice to here it works for you :)
Moggy
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Re: EPROM for 4K ZX80 ROM?

Post by Moggy »

I would have to add that my programmer is an ancient device for the ZX81 or ZX spectrum but the point still follows that 3 batteries is sufficient.
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RetroByte
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Re: EPROM for 4K ZX80 ROM?

Post by RetroByte »

That's cool :)
Moggy
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Re: EPROM for 4K ZX80 ROM?

Post by Moggy »

Further to the above if you do use an external supply then some method must be used to obtain either 21 or 25 volts. The three batteries put out 27v and in my programmers case a small onboard dropper circuit ( zener diode and resisters I think ) is used for required voltages.
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