QL issue 5 modification for 27C512

[Levas]

Hi All,
I resurrected QL issue 5 (version with 3 EPROMs) from dead state (bad ROM!) and converted to single 27C512 ROM usage. There is few small modifications and one very hard- need to cut A15 pin on EPROM connected to Vcc on PCB under the socket.
I have all documented in Lithuanian language at my web page and maybe in future I will translate it to English.
I am new to QL computer (4 days only), so I don't know if such modification is interesting for this forum participants.

First I was using additional PCB as I didn't know where was the problem in this computer, but after it started I modified PCB to fit all nice.

The web page in Lithuanian language is here:
http://www.vabolis.lt/2020/12/04/sinclair-ql-remontas/

[Andrew]

It seems that the modifications are functionally the same as the modifications already documented in the QL Service Manual, Minerva documentation (http://www.dilwyn.me.uk/docs/manuals/mi ... ual_11.pdf - section 'Fitting (MKI)' on page 62, under the heading 'AH Conversion') and in QL-SD manual (https://www.kilgus.net/soft/QL-SDv2_User_Manual.pdf - section 4.3 ROM AH COnversion)

[Levas]

A just a bit similar, but 27C512 use A15 pin and it is hard connected to Vcc on QL mainboard. This mod is connecting EPROM without bent legs and any hanging PCB or other items. Must work with original ROMs too.

[Pr0f]

Do you have to remove the socket to cut the track, or can you get the knife in - I can see that thick trace that comes in from the left hand side - VCC - that feeds across the other ROM socket - which means the Minerva must go in the right most socket.

I've done something similar in the past - but used a low profile socket piggy backed onto the first, with the pin 1 bent under and fed by a flying wire to the patch area where A15 can also be found, and OE / CE tied together, as the ROM socket uses CE pin to select which ROM to use normally - one is active high, the other active low select (which is why they can be wired piggy back).

[Levas]

Hi All,
I have done some translation in English language.
http://www.savel.org/2020/12/19/sinclai ... for-eprom/

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