Hello to all, My first Atari Projects so general advice please

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Lplate
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Hello to all, My first Atari Projects so general advice please

Postby Lplate » Sat Oct 06, 2018 10:36 pm

Hello everyone, my first post and atari projects have lead me here :)

Projects A is a 520STFM C103414-001 REV 1.1 (2 chip ROM not sure but maybe TOS 1.04???
Fault = Hanging at white screen
History = None, came to me missing screws and bottom ROM IC overheating.
Tried = Removed ROM'S straightened bent pin and replaced, (No more over heating but no change), tried removing floppy (worked in other machine) tried another PSU that also worked in other machine, Checked i am getting 5 and 12v in obvious places and also tried re flowing solder joints on ROM sockets and CPU.

Questions:
a: what does hanging on a white screen indicate? No cpu activity, ram problem, glue chip?
b: is this likely to be dead ROM IC due to the bent pin/overheating?

This is a picture of the board.....
Image

Project B is a 1040STFM 070523-001 REV D (6 chip ROM maybe 1.0 or 1.02 TOS. This was advertised as a 520STFM
Fault = Green and purple Lines, no activity
History = Purchased a week ago in "working" condition but had a faulty drive. Advertised as a 520 and in a 520 case so i purchased it thinking i could use it as known good parts to help fix "project a" but have realised it is a 1040 and has differences. I fitted drive from the 520 above and tried over 50 games with no problems. I then ordered the rubber band to replace in the original floppy drive, It arrived and was fitted. I turned the machine on and immediately saw purple and green lines "pictured below" :( Turned machine off immediate and removed floppy but same issue.
I then tried removing and re seating all socketed IC's. Everything was ok until i put the shifter chip the wrong way round :oops: now went to no display "i killed the poor little shifter" Ok so dead chip, nothing to loose so i took shifter from the 520 and after placed into 1040 i have display again but still purple and green stripes :)
Tried: Different PSU, Keyboard,

Questions:
a: what causes these purple and green lines. All i did was fit original floppy drive with new band to this machine and it went from loading every game i had, to a no boot striped screen, what did i do to kill it? :shrug:
b: Could a problem with the floppy of effect the floppy controller ic and would it be worth changing or does the lines indicate something else?

Picture of board..
Image

Picture of lines..
Image

I will admit i am an Atari noob but i do regularly work on phones, laptops and other hardware. I have only ever played games on atari's as a child but this is a lovely little project for me and after reading the posts here on the forums i had to join up. Any pointers or things to try are welcome guys!
Sometimes I'm drunk and sometimes I'm sober, but most of the time I'm just plain old me :shrug:

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Arne
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Re: Hello to all, My first Atari Projects so general advice please

Postby Arne » Sun Oct 07, 2018 6:39 am

Lplate wrote:Projects A is a 520STFM C103414-001 REV 1.1 (2 chip ROM not sure but maybe TOS 1.04???
Fault = Hanging at white screen
History = None, came to me missing screws and bottom ROM IC overheating.
Tried = Removed ROM'S straightened bent pin and replaced, (No more over heating but no change), tried removing floppy (worked in other machine) tried another PSU that also worked in other machine, Checked i am getting 5 and 12v in obvious places and also tried re flowing solder joints on ROM sockets and CPU.

Questions:
a: what does hanging on a white screen indicate? No cpu activity, ram problem, glue chip?
b: is this likely to be dead ROM IC due to the bent pin/overheating?

Overheating is rarely positive.
You have to distinguish a white screen on a color monitor (SC1224 etc) or monochrome monitor (SM124...). It makes a difference.
The schematics/service manual might be helpful. You can download them at my homepage.

Lplate wrote:Questions:
a: what causes these purple and green lines. All i did was fit original floppy drive with new band to this machine and it went from loading every game i had, to a no boot striped screen, what did i do to kill it? :shrug:
b: Could a problem with the floppy of effect the floppy controller ic and would it be worth changing or does the lines indicate something else?

a: could be MMU, drivers/latches 74LS244/373 or RAM
All i did was fit original floppy drive with new band to this machine
So you moved the ST. Have a look at the PLCC68 socket contacts. These may become corroded over time or the pins do not have the force to make contact withthe IC's pins anymore. Take a magnifying glass and have a look.
b: ahh... no. don't think so.

Anyway: get the service manual and check the chapter "Troubleshooting a dead unit"

Good luck
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Lplate
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Re: Hello to all, My first Atari Projects so general advice please

Postby Lplate » Sun Oct 07, 2018 4:11 pm

Arne wrote:Overheating is rarely positive.
You have to distinguish a white screen on a color monitor (SC1224 etc) or monochrome monitor (SM124...). It makes a difference.
The schematics/service manual might be helpful. You can download them at my homepage.


Thanks for replying, I found the proper manual late last night and will be reading over it today & probably lots in the future too. RE:monitor, i don't have a colour monitor so using a "LCD TV" or a sm124.
The white screen 520st "project a" displays the same on both but i can no longer verify this as i have taken the shifter for the 1040 and will need to get one ordered (getting sockets too). Will update once i have read over the manual and the shifter IC and my white screen back lol

Would you mind elaborating on what difference i would be distinguishing and what to look for please as i dont have a colour monitor.

The other 1040 "project b" displayed fine and played games on both my LCD and the SM124 but since it failed it will only show the purple and green striped on my TV, i no longer get any kind of display on the SM124 and dont know what this means so am off to read through that manual.....


a: could be MMU, drivers/latches 74LS244/373 or RAM


My MMU and GLUE are socketed on the 1040 but not the 520 and are slightly different so i think i would need replacements to try, im looking into this. Not sure how to go about the driver/latches thing to be honest but ive looked up the 74S244 and its simple to replace and source so can definitely look more into that, thanks.

The Ram is a scary thing for me on the 1040 as its 16 IC's as appose to the 4 on the 520 8O
I have no idea how to narrow this down until i have some answers to other questions. For example is it possible to disable 1 IC at a time and the machine to still boot? if so what would be the minimum amount that has to be on the board.
I have already confirmed i have power at RAM blocks but would appreciate any guidance regards a sensible and efficient way to rule RAM out?



So you moved the ST.
:lol: :lol: :lol: Love it!

Have a look at the PLCC68 socket contacts. These may become corroded over time or the pins do not have the force to make contact withthe IC's pins anymore. Take a magnifying glass and have a look.
b: ahh... no. don't think so.


PLCC68 is the blitter right? If so i dont see it on the 1040 or the 520 but the 520 does have an empty space for it. I had a really good look under the scope for any loss of contact on glue and MMU sockets/chips and all looks fine, they were removed and re-seated too but still stripes :) I did notice some cracked joints on some of the RAM chips so i re flowed all the one's i could see with weak joints but no cigar... :coffe:

i still have lots to read, learn and try so off to read the manual now, any further thoughts, answers or other information is welcome, thanks
Sometimes I'm drunk and sometimes I'm sober, but most of the time I'm just plain old me :shrug:

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Re: Hello to all, My first Atari Projects so general advice please

Postby Arne » Mon Oct 08, 2018 4:51 am

Lplate wrote:Would you mind elaborating on what difference i would be distinguishing and what to look for please as i dont have a colour monitor.

White screen on a TV/SC1224 can mean that the CPU cannot access ROM. White screen on a SM124 should mean that it can access ROM. The reason is the hardware and TOS. As you can see in the schematic MONO_DETECT from the monitor plug is pulled high. The SM124 pulls it low. So a white screen (=initialised) on a SM124 means that the MFP detection for MONO_DETECT worked.
On a color monitor you cannot be sure if TOS already moved over the code for MONO_DETECT or is stuck at the very beginning.

That's what I know - but I might be wrong on this one.
At least a white screen on a SM124 means that Glue provides HSYNC and VSYNC

Lplate wrote:The Ram is a scary thing for me on the 1040 as its 16 IC's as appose to the 4 on the 520

Take a scope and check if there is activity on /CAS and /RAS the check the data-lines for activity. Start with bank #0

Lplate wrote:For example is it possible to disable 1 IC at a time and the machine to still boot?

Nope - would you boot without an arm/leg...?

Lplate wrote:if so what would be the minimum amount that has to be on the board.

16 data-lines want to be satisfied with 0s and 1s.

Lplate wrote:PLCC68 is the blitter right?

Yes Blitter - but not in your case. MMU/Glue are PLCC68, too.
Last edited by Arne on Mon Oct 08, 2018 5:29 pm, edited 1 time in total.
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Latz
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Re: Hello to all, My first Atari Projects so general advice please

Postby Latz » Mon Oct 08, 2018 6:41 am

Hi,
just an idea about "project 2" (1040): Double- , well better triple-check that floppy ribbon cable is connected in the correct direction.
From my Falcons i know that there´s no "security slot" and so the floppy connector can be mounted in both directions...

Latz
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Lplate
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Re: Hello to all, My first Atari Projects so general advice please

Postby Lplate » Mon Oct 08, 2018 11:18 am

White screen on a TV/SC1224 can mean that the CPU cannot access ROM. White screen on a SM124 should mean that it can access ROM. The reason is the hardware and TOS. As you can see in the schematic MONO_DETECT from the monitor plug is pulled high. The SM124 pulls it low. So a white screen (=initialised) on a SM124 means that the MFP detection for MONO_DETECT worked.
On a color monitor you cannot be sure if TOS already moved over the code for MONO_DETECT or is stuck at the very beginning.

That's what I know - but I might be wrong on this one.
At least a white screen on a SM124 means that Glue provides HSYNC and VSYNC


Very useful info for me, i will be referring back to this, thank you.
A scope is on my shopping list but i don't have one right now so will rule out what i can for the time being.

Going by schematic and what it says to swap..

White screen = SWAP OUT SHIFTER CHIP/ MEMORY CONTROLLER CHIP/GLUE CHIP
Scrambled =SWAP OUT REPLACE (1) GLUE CHIP/(2) SHIFTER CHIP/(3) MEMORY CONTROLLER
Black Screen = (1)SWAP GLUE(2) SWAP SHIFTER

The 1040 scrambled has the shifter from the 520 so has been swapped without change. Im ordering the GLUE IC to try. I wasn't sure at the time if "MEMORY CONTROLLER" was refered to as the DMA or the MMU but as i had a spare C025913 – 38 – STFM DMA on the 520 i decided to borrow it while i try and source a replacement shifter IC for the 520.
Results were the same "striped screen"on the 1040, however when de-soldering the DMA from the 520 some of the contacts/pads completely disintegrated. I have not seen contacts that bad other than on water damaged hardware but no sign of that here. This makes me think that the originally problem for the 520 "white screen" could be those very contacts!

I have ordered sockets for the DMA and other ICS just in case and will rework and repair that area but also need the shifter IC to proceed with that project. I do feel that it's likely the bad contacts causing that white screen and am looking forward to finding out ;)

Back to the 1040.....

Hi,
just an idea about "project 2" (1040): Double- , well better triple-check that floppy ribbon cable is connected in the correct direction.
From my Falcons i know that there´s no "security slot" and so the floppy connector can be mounted in both directions...

Latz


I really think this is what has happened, i have been thinking about this and trying to replay all i have done. I just laid everything out and went over what i did when swapping the drives initially. What i found is that with the "original" drive in place compared to the replacement taken from the 520, the cables are opposite sides. I remember "now" when initially trying to replace the drive i have some trouble with the cables reaching so i removed the top shield and was testing all the games like this while i waited for the rubber band for original drive.

Position of cables..
Original drive = power cable above IDE cable (towards back of unit)
520 Drive = power cable below IDE cable (towards front of unit)

The original drive was fully assemble and i did not check it was upside down, whats more is the cables looked so naturally in position that i just plugged the drive in. Meaning the IDE cable was plugged in upside down as you say.
I cant say this 100% but im pretty sure this is what has happened if it is the likely cause of my problem?

After thinking about this i came back to something i said earlier regarding the floppy disk controller becoming damaged. I was going to change it but i have sockets on the way so may as well wait for them to arrive first.

What do you guys think? Floppy IDE cable the wrong way round maybe killed the floppy controller IC? Any other damage this mistake would cause? This does seem like the issue to me as the only change between working and not is the floppy drive being plugged in.
Sometimes I'm drunk and sometimes I'm sober, but most of the time I'm just plain old me :shrug:

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Arne
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Re: Hello to all, My first Atari Projects so general advice please

Postby Arne » Mon Oct 08, 2018 1:01 pm

Lplate wrote:
Hi,
just an idea about "project 2" (1040): Double- , well better triple-check that floppy ribbon cable is connected in the correct direction.
From my Falcons i know that there´s no "security slot" and so the floppy connector can be mounted in both directions...

Latz


I really think this is what has happened, (...)


Doesn't matter at all. If you plug in the FDD cable twisted and switch on the machine then... the access LED glows all the time. And that's it.
It will not harm your ST. Same on PCs. Happened to me a couple of times, too.

Besides:
Lplate wrote:Original drive = power cable above IDE cable (towards back of unit)


520/1040 do not come with IDE! You have to upgrade it to IDE.
IDE = 40pin ribbon cable
FDD = 34pin ribbon cable
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Re: Hello to all, My first Atari Projects so general advice please

Postby Dal » Mon Oct 08, 2018 2:50 pm

Dumb question, but did you leave the white screen ST on for longer than 40 seconds? If the ST isn't able to read a disk, then it can take over 40 seconds for the desktop to appear.
Mega"SST" 12, MegaSTE, STE: Desktopper case, IDE interface, UltraSatan (8GB + 512Mb) + HXC floppy emulator. Plus some STE's/STFM's

Lplate
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Re: Hello to all, My first Atari Projects so general advice please

Postby Lplate » Mon Oct 08, 2018 5:32 pm

Doesn't matter at all. If you plug in the FDD cable twisted and switch on the machine then... the access LED glows all the time. And that's it.
It will not harm your ST. Same on PCs. Happened to me a couple of times, too.


Bad news, i thought i may have been on to something :(

520/1040 do not come with IDE! You have to upgrade it to IDE.


Apologies, i haven't dealt with these old cables in a very long time, they are standard FDD cables :oops:

Dumb question, but did you leave the white screen ST on for longer than 40 seconds? If the ST isn't able to read a disk, then it can take over 40 seconds for the desktop to appear.


Not dumb at all, when i first got that one i had no clue whatsoever about how they turn and and their normal behaviour, luckily one of the first threads i read on here mentioned it taking a lot longer to boot with no floppy so i left it 5-10 minutes a few times.
This was done on my TV however, not on the SM124 and as i have taken the shifter i need a replacement before i can verify the MONO_DETECT or anything else with this one.

If anyone has a SHIFTER for sale i am in the UK and would be happy to pay for one. My IC is "C025914-38A PH23-024 6M1 41"
I have seen a few but slightly different numbers and not sure what ones may also be suitable?

Once i receive the sockets im going to re socket most of the IC's. After seeing them bad solder joints it seems a good idea as any problem pads will reveal themselves and allow me to ensure all contacts are solid in the process. Will also make future diagnostics easier too. Next on my list is the GLUE IC for the 1040. Thanks for all the input guys, will await parts and update of any changes.
Sometimes I'm drunk and sometimes I'm sober, but most of the time I'm just plain old me :shrug:

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Arne
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Re: Hello to all, My first Atari Projects so general advice please

Postby Arne » Mon Oct 08, 2018 6:12 pm

Lplate wrote:Bad news, i thought i may have been on to something :(

Good news. You don't have to unsolder the FDC!

Lplate wrote:If anyone has a SHIFTER for sale i am in the UK and would be happy to pay for one. My IC is "C025914-38A PH23-024 6M1 41"
I have seen a few but slightly different numbers and not sure what ones may also be suitable?

You may order one from Chris: https://www.exxoshost.co.uk/atari/last/storenew/

Lplate wrote:Once i receive the sockets im going to re socket most of the IC's.

I do NOT advise this until absolutely necessary i.e. the IC is proven to be defective.
Unnecessary (un)soldering can make the vias break and will produce new errors.

BTW: MONO_DETECT runs to the MFP so you can check its habits without a shifter plugged in.
Read the schematics!
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