ALPHA MODIFICATIONS

All information relating to the Alpha plus all the WIP threads etc.
Post Reply
User avatar
exxos
Site Admin
Site Admin
Posts: 23499
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

ALPHA MODIFICATIONS

Post by exxos »

Started a new thread for "must do" fixes and mods etc.
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
User avatar
exxos
Site Admin
Site Admin
Posts: 23499
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: ALPHA MODIFICATIONS

Post by exxos »

JUMPER PADS
links.jpg
links.jpg (80.51 KiB) Viewed 7770 times

SJ1 & SJ2 are the 2 solder pads like on the STFM near the blitter. Pads must be shorted when NOT using the blitter, and OPEN when using the blitter. For now I would suggest not fitting the blitter.

SJ5 is the clock line for the CPU, this needs to be soldered to allow 8MHz clock to CPU.

SJ3 & SJ4 Need to both be linked.

(Jumpers were there with intention of adding boosters without cutting tracks at a later date )

Jumper next to the ROM is the TOS104 / TOS102 select line.
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
User avatar
exxos
Site Admin
Site Admin
Posts: 23499
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: ALPHA MODIFICATIONS

Post by exxos »

RESET FIX

First is the short as found by icky on the reset circuit https://www.exxosforum.co.uk/forum/viewt ... 1171#p9633


The red circle shows the resistor shorting out VCC to the highlighted yellow line..
1.JPG
1.JPG (55.25 KiB) Viewed 7730 times

SOLUTION


STEP 1:
s1.JPG
s1.JPG (53.48 KiB) Viewed 7730 times
Cut the tracks on the bottom of the pcb where the yellow lines are.



STEP 2:
s3.JPG
s3.JPG (56.88 KiB) Viewed 7730 times
Solder a wire on the bottom of the PCB to join the pads highlighted with a yellow circle.

DONE:
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
User avatar
Icky
Site Admin
Site Admin
Posts: 3986
Joined: Sun Sep 03, 2017 10:57 am
Location: UK

Re: ALPHA MODIFICATIONS

Post by Icky »

exxos wrote: Mon Sep 10, 2018 10:05 am If anyone can post a image of this fix then it would help...
As requested two images. Excuse the messy soldering / flux etc on the underside :oops:

IMG_3034.png
IMG_3034.png (419.7 KiB) Viewed 7696 times

Track cuts are under the wire patch

IMG_3032 (1).png
IMG_3032 (1).png (367.9 KiB) Viewed 7696 times
User avatar
exxos
Site Admin
Site Admin
Posts: 23499
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: ALPHA MODIFICATIONS

Post by exxos »

Icky wrote: Mon Sep 10, 2018 10:24 pm As requested two images. Excuse the messy soldering / flux etc on the underside :oops:
:bravo:
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
User avatar
exxos
Site Admin
Site Admin
Posts: 23499
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: ALPHA MODIFICATIONS

Post by exxos »

HSYNC FIX

from here https://www.exxosforum.co.uk/forum/viewt ... t=90#p9961

I ballsed up the Hsync and it needs a fix to bypass the inverter...

d1.JPG
d1.JPG (49.49 KiB) Viewed 7594 times
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
User avatar
Icky
Site Admin
Site Admin
Posts: 3986
Joined: Sun Sep 03, 2017 10:57 am
Location: UK

Re: ALPHA MODIFICATIONS

Post by Icky »

exxos wrote: Sun Sep 16, 2018 10:30 pm HSYNC FIX

from here https://www.exxosforum.co.uk/forum/viewt ... t=90#p9961
I just sat down to start doing some work on the board tonight and thought I would tackle this first.

Fix in place but am still getting horizontal scrolling as per video of boot before fix.

Will take a closer look at the circuit to see whats going on.
Realloy
Posts: 8
Joined: Mon Jul 30, 2018 8:18 pm
Location: Sweden

Re: ALPHA MODIFICATIONS

Post by Realloy »

After cutting the trace on both sides of R920 ,,,, measure between D7 and the cut free R920 i get zero ohm, those two point must go to positive plane in pcb, so i guess no need to move the R920.

And also i noticed that the holes for the PSU is mirrored on the PCB.. Maybe you already know this..
User avatar
exxos
Site Admin
Site Admin
Posts: 23499
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: ALPHA MODIFICATIONS

Post by exxos »

Realloy wrote: Sun Sep 16, 2018 11:55 pm After cutting the trace on both sides of R920 ,,,, measure between D7 and the cut free R920 i get zero ohm, those two point must go to positive plane in pcb, so i guess no need to move the R920.
ahh yep, The left link wire isn't needed as the resistor itself actually connects to vcc.. will update the info...
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
Realloy
Posts: 8
Joined: Mon Jul 30, 2018 8:18 pm
Location: Sweden

Re: ALPHA MODIFICATIONS

Post by Realloy »

i can see all the chips have a decoupling capacitor,,, but what about BAD DMA ? is there one and where? or is it not necessary?
Post Reply

Return to “ALPHA DEVELOPMENT INFO”