[sdiy] PROM Replacement for Spider

[Raf Wlodarczyk]

I used the "Orphan Programmer".  Not many devices will program parts with -41V :)  This will be a read only situation, the PROM isnt written to when in use
> On 01/27/2026 2:53 PM EST grant musictechnologiesgroup.com <grant at musictechnologiesgroup.com> wrote:
> 
>  
> What did you use for a programmer!? That's a pretty unique (oddball) 
> part: 512 *bytes*.  No matter what parallel chip you use, it's going to 
> require an adapter of some sort.  2732 looks closest, assuming your 
> programmer can handle it. Otherwise I guess it doesn't really matter. 
> How are the control lines E1*, E2*, S* attached? One for chip select and 
> the other two grounded (or perhaps one to an address line)?
> 
> GB
> 
> On 1/27/2026 8:39 AM, Raf Wlodarczyk wrote:
> > The digiky ones come from Rochester and ALL the ones (i bought 50 of each type) I got from them were bad, partial writes, wouldnt clear etc.  I'll look at the AT27, thanks for the suggestion
> >
> >> On 01/27/2026 11:26 AM EST Roman Sowa <modular at go2.pl> wrote:
> >>
> >>   
> >> DigiKey has a thousand of them, but anyway, I wouldn't buy them because
> >> of the price and age.
> >> Whenever I need to replace old EPROM I pick most common, cheapest and
> >> easy to get OTP EPROM, which usually is AT27C256. It has 28 pins so 4 of
> >> them will be outside of the socket, which typically can fit on the old
> >> board without pushing other components. After programming just wire 5
> >> pins together: 1,2,26,27,28
> >>
> >> Or you may fance making breakout board for PLCC EPROM
> >>
> >> forget about buying newly made EPROM smaller than 256kb
> >>
> >> Roman
> >>
> >> W dniu 2026-01-27 o 16:16, Raf Wlodarczyk pisze:
> >>> Hello list,
> >>>
> >>> The supply of the IM6654 PROM i use in my Spider clone has dried up and was wondering if anyone had suggestions on how to use a modern part for a replacement.  IM6654 is a 8x512B device so could using a AT28C512 on an adapter do the trick?  My PROM/EEPROM knowledge is limited so any help would be greatly appreciated.
> >>>
> >>> -R
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