Hi everyone
I have a black box with an AH Rom set inside. The AH rom (one half) is piggy backed (two chips soldered together)and has a flying lead from one pin to a point further along the main circuit board.
My question is really about how (or if) you can upgrade the ROM set to JM or JS or even replace with a QL-SD card.
In particular what would be done with the flying lead from the rom labelled QLAH 8600 66CC and the lead appears to be on pin 20 (counting anticlockwise.
Any help or pointers to documentation gratefully received
AH Rom BBQL
-
martyn_hill
- QL Wafer Drive
- Posts: 1102
- Joined: Sat Oct 25, 2014 9:53 am
Re: AH Rom BBQL
Hi kmman!
Having recently upgraded a 2nd hand AH/EPROM-based QL to a Minerva EPROM, I can confirm that its perfectly do-able - assuming you're confident with a soldering iron.
Its actually been documented quite nicely in the Minerva User Guide - see section 'Fitting (MK1)' paying attention to the sub-section 'AH Conversion' on page 62.
See what you make of those instructions and let us know if you have any further questions.
Some background that might help you understand why the instructions tell you to do it like they do, but feel free to stop reading here if those instructions prove sufficient in themselves.
Sinclair switched a couple of times in the early (Issue 5) motherboards between EPROM and ROM and of different capacities, across the 2 ROM sockets.
To accommodate the variety of builds, an extra TTL IC (the ubiquitous 74x00 Quad-NAND) appears, along with some 'zero' Ohm resistors - and place-holders for others. These 0-ohm resistors are marked with just a single black stripe and are simply wire-links - apparently they're easier for automated assembly equipment to fit than fiddly bit of wire...
Which of these 'link' resistors are fitted is determined by the different pin-out requirements across the different EPROM/ROMs fitted.
Your description sounds just like my own Issue 5 - 3x 16k EPROM, 2 of which are 'piggy-backed' in to the same socket - the 'flying-lead' providing the chip select for the upper 16k, whilst the lower chip is enabled directly from the motherboard (and one of the 74x00 NAND outputs).
Ultimately, to move to a Minerva EPROM and/or the QL-SD (64k, possibly with the upper 16k left 'free' for the external ROM-socket) you will switch around the link resistors as described in the Minerva guide and will dis-connect the flying lead altogether.
Good luck!
Having recently upgraded a 2nd hand AH/EPROM-based QL to a Minerva EPROM, I can confirm that its perfectly do-able - assuming you're confident with a soldering iron.
Its actually been documented quite nicely in the Minerva User Guide - see section 'Fitting (MK1)' paying attention to the sub-section 'AH Conversion' on page 62.
See what you make of those instructions and let us know if you have any further questions.
Some background that might help you understand why the instructions tell you to do it like they do, but feel free to stop reading here if those instructions prove sufficient in themselves.
Sinclair switched a couple of times in the early (Issue 5) motherboards between EPROM and ROM and of different capacities, across the 2 ROM sockets.
To accommodate the variety of builds, an extra TTL IC (the ubiquitous 74x00 Quad-NAND) appears, along with some 'zero' Ohm resistors - and place-holders for others. These 0-ohm resistors are marked with just a single black stripe and are simply wire-links - apparently they're easier for automated assembly equipment to fit than fiddly bit of wire...
Which of these 'link' resistors are fitted is determined by the different pin-out requirements across the different EPROM/ROMs fitted.
Your description sounds just like my own Issue 5 - 3x 16k EPROM, 2 of which are 'piggy-backed' in to the same socket - the 'flying-lead' providing the chip select for the upper 16k, whilst the lower chip is enabled directly from the motherboard (and one of the 74x00 NAND outputs).
Ultimately, to move to a Minerva EPROM and/or the QL-SD (64k, possibly with the upper 16k left 'free' for the external ROM-socket) you will switch around the link resistors as described in the Minerva guide and will dis-connect the flying lead altogether.
Good luck!
Re: AH Rom BBQL
Hi Martyn
Thank you for the response to my query. I do have the internal QL configuration you describe. Having downloaded the Minerva user manual I have found the instructions and can hopefully proceed.
I will first look to see if I can find a schematic or image of the series 5 board (or at least the relevant section of it) to make certain I am making the necessary (correct) adjustments as the board itself does not have very clear labelling.
Once again - thanks
Kevin
Thank you for the response to my query. I do have the internal QL configuration you describe. Having downloaded the Minerva user manual I have found the instructions and can hopefully proceed.
I will first look to see if I can find a schematic or image of the series 5 board (or at least the relevant section of it) to make certain I am making the necessary (correct) adjustments as the board itself does not have very clear labelling.
Once again - thanks
Kevin
Re: AH Rom BBQL
Hi Martyn
Found the component layout for the series 5 board here http://www.sinclairql.net/srv/index.html
Kevin
Found the component layout for the series 5 board here http://www.sinclairql.net/srv/index.html
Kevin
-
1024MAK
- Super Gold Card
- Posts: 593
- Joined: Sun Dec 11, 2011 1:16 am
- Location: Looking forward to summer in Somerset, UK...
Re: AH Rom BBQL
Standby alert “There are four lights!”
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer in Somerset later in the year
QL, Falcon, Atari 520STFM, Atari 1040STE, more PC's than I care to count and an assortment of 8 bit micros (Sinclair and Acorn)(nearly forgot the Psion's)