[ATARI 1040Stf] Not working

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[ATARI 1040Stf] Not working

Postby realac0 » Thu Jul 04, 2019 3:29 pm

Hi, i'am a collector, for fun. Mostly Cbm stuffs.
anyway i have an Atari 800xl a 2600 and a 7800 too, with some cartridges and software.
i know how to use OSC/Tester, i am able to desolder and socket etc and i know how to make some bridge wires if needed.

well, i got a 1040STf unknow state, payed decent price.
the machine is in good state, but no video cable. I've ordered one from Ebay (RGB Scart).
while i'am waiting for the cable, i've decided to test the machine, arrived today.

green led light up, but no floppy spinning, and no light on floppy.
i opened the case for reseat socketed chips and i noticed:

1) there are very few chips socketed, and this board got already reworked
2) 68000 is a desoldered one (some solder and flux on pins), socket seem fine
3) other 2 or 3 chips got desoldered.
4) on total, there are only 4 chips socketed + the 2 with strange package (i think are called glue logic)

well, all that said, i have rework some pins with new solder (lot of fllux residue before) and all seem fine.
tried again power up, but nothing changed, no floppy activity
so i've power up oscilloscope and i've tested:

Pin 15 clock : OK
Pin 17 reset : OK

but ...

all Addresses (A1 etc.) are stuck, no activity at all

seem to me clear that CPU is just not addressing things.

if we was talking about a C64, i was going to replace PLA first, and then check rams.

but have zero experience on Atari St's, so i am asking u what i should do.
i've check the traces on sure reworked chips and seem fine.
there is a bit of corrosion, around the pcb that i've already cleaned with ISO Alcool and checked continuity are fine (not tested everything of course).

i'am waiting the video cable, and maybe i get more info's from connecting to video but, on my opinion, this will be 99,9% a blank screen

any ideas where i should start?
thank you
Federico from Italy (sorry for my bad english)

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Re: [ATARI 1040Stf] Not working

Postby realac0 » Thu Jul 04, 2019 7:34 pm

little update

i was wrong about the reset, sorry, first time i probe a 68k
18 reset is high, but 17 is low, and, according to troubleshooting dead computer on Service Manual, i should have on HALT an high.
so i've check schematics and looked for the inverters. I've found a 74ls05 (on my manchine is a 74htc05 something) and a 566.
i procedeed desolder , socked and test
i have no spare 7405, but i've tested it with tl866 and test give me ok so i've put the desoldered one on socket
i have a spare 566 so i've changed it
replugged the psu , tested HALT pin17, still low.
i changed the 4700uf cap too because was already reworked (not original) and on my opinion was not well soldered (test cap give ok anyway).

now, after connect keyboard and drive, if i power up i get the orange led up too (before was only the green power led up, the drive
led was death).
i have some disks, and have try to put into the drive.
i can hear, very very slow noise if i insert a disk on floppy.
if no floppy, nothing, just orange led up.

i've try leave the 1040st powered for a bit, so , maybe, he go on tos , but the orange led never leave, always stay on

anyway, still no activities on addresses of 68k and pin17 still low ...

will wait for the rgb cable and see what happen on video (will be 99% blank screen on my opinion)

... this machine seem to have some serious issues

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Re: [ATARI 1040Stf] Not working

Postby mlynn1974 » Thu Jul 04, 2019 10:23 pm

Hi,
I don't know if you know but on the ST without a floppy in the drive it will take about 20 seconds to display the desktop.

There might be other reasons why the floppy LED would stay on, but if the 68k has no activity on the address bus then it hasn't been able to run any code in ROM so it shouldn't even be attempting to activate the floppy drive.

Check this topic:
http://www.atari-forum.com/viewtopic.php?t=23151

Power up the computer. Using an oscilloscope, verify the 8MHz clock to the 68000 CPU (pin 15). Replace oscillator if necessary. Then check pin 17 (HALT) of the 68000 CPU. It should be a TTL high. If so, go on to 3 below. If not, the CPU is halted. The reasons may be: (1) bad reset circuit, (2) double bus error, (3) bad CPU.

Good luck! Welcome to the forum.
Still got, still working: Atari 4Mb STe, 520STFM, 2.5Mb STF.
Hardware: Cumana CSA 354, Ultimate Ripper, Blitz Turbo, Synchro Express II (US and UK Versions).

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Re: [ATARI 1040Stf] Not working

Postby realac0 » Fri Jul 05, 2019 1:03 pm

i've already read what u quoted.
on pin 15 cpu (clock) i have 8Mhz stable and fine, on the 17 (HALT) i have low, and should be HIGH.
i've check che reset circuit and seem fine for what i can undestand (socketed 7405 and 566, and if i pull out the 68k pin 17 is down for 0,5 seconds than go up, so i think this mean reset circuit is ok ... )
i've try another known working 68k (from my A500) and same thing, so i can exclude problems on CPU.
with CPU on socket, pin 17 go back to low (go high for a bit then low)
as suggested on service manual, i've check pin22 CPU BERR and is always high

so i'am left with this:

----------
If still failing, the CPU is unable to read ROM or there is a component which is not responding to a read or write by the CPU, probably the MFP 68901 or DMA Controller. 'Ihe MFP should respond to an MFPCS with DTACK. 'The DMA chip should respond to FCS by asserting RDY. 'Ihere is no way to check (3) other than by elimination of the other two possiblities, although a hot CPU (too hot to touch for more than a second) strongly indicates a bad CPU
----------

i don't understand what he mean with the 68901 and DMA tests ...

all i can say is that i've found the pinout of 68901 MFP and checking with OSC i got:
Pin48 (CS) is HIGH
Pin46 (DTACK) is HIGH

about the DMA, looking at the ST schematics, i've found that:
Pin39 CLK is ok, clock
Pin38 RDY is low
Pin3 FCS is High (not easy read if correct Pin3, because i can find pinout only on schematics about dma)

if CPU not bad, can be DMA? are these readings ok?
The machine continue to stay stuck high on bus , green and orange led illuminated and nothing more happen
i still can't connect to a monitor, video cable not arrived ;(

only things pulsing on this damn ST are clocks and my balls (because everything else is stuck :lol: :D 8O 8O )

thankyou
Federico

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Re: [ATARI 1040Stf] Not working

Postby mlynn1974 » Fri Jul 05, 2019 1:25 pm

It might be worth checking this:
viewtopic.php?f=15&t=31985
You should download Atari ST Internals if you don't have a copy already.

In that case it turned out to be a bad RAM chip. Are all the RAM chips the same brand?
If the 68k is good on your machine best to check the condition, solder joints and resistors attached to the RAM chips.
Still got, still working: Atari 4Mb STe, 520STFM, 2.5Mb STF.
Hardware: Cumana CSA 354, Ultimate Ripper, Blitz Turbo, Synchro Express II (US and UK Versions).

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Re: [ATARI 1040Stf] Not working

Postby realac0 » Fri Jul 05, 2019 11:08 pm

i've checked the ram and is damn smd, never worked on it ...
anyway are not all same brand, some are different.
too hard for me, i usually just desolder and change everything till i find the problem ;)
on cbm stuffs, but i have some idea where to check, on this ST, really, i have no idea from where to start ...
maybe desolder MFP and DMA and look if some activity start on bus?
or if halt signal go high?
need to buy replacements ... big work ...

anyway

when i 've changed the 68k, when the CPU is out of socket, pin17 is high, as should be with reset circuit, dunno if this is correct

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Re: [ATARI 1040Stf] Not working

Postby realac0 » Sat Jul 06, 2019 7:20 am

i've downloaded Atari Internals, and have give a read.
anyway, the post u linked me, is from a guy with mutch more experience than me.
i don't have a Logic Analizer, just a OSC and Multimeter and, anyway, i have not the skill for this type of troubleshooting.
i'am more a "desolder this and try this" guy ;)
this Atari is very hard for me because i don't know nothing about this computer and i have no spares so, before buy some rep, i should at least have some direction to go (DMA? MFP? etc.). Last but not least, is everything dead, i can't just follow the schematics on BUS for find something wrong on a address line ... this is just totally dead.
on a C64 this problems (totally dead bus) point me direct to PLA ... but ... here?


some more infos:

this is the PCB of my Atari 1040STf

Image

(not mine, but is the same)
i got full populated ram, this seem to have 512k
and i got only 2 TOS ROMS (U63/U67)

i noted that, on my PCB, resistors R71 / R72 / R73 got reworked.
i've read somewhere that this is intended to disable/enable upper or lower 512k RAM
seem the guy that have reworked this PCB tryed to deactivate it, because i see solder on one leg.
i think , maybe for tests , he cut the leg from upper board (component side) and, then , solder the joint on this side

maybe this can help point me somewhere to start some action.

my opinion is start with desoldering/socketing MFP and DMA and maybe cut/desolder R71/R72/R73

after this, i can try check if, removing something of these components give HIGH on HALT

what u think?
Last edited by realac0 on Sat Jul 06, 2019 7:25 am, edited 2 times in total.

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Re: [ATARI 1040Stf] Not working

Postby DoG » Sat Jul 06, 2019 8:14 am

Check if your ROM chips is in the correct order, HI, LO. Check solder blob on A16, A17 and CE is on 1M. You also need a 74LS11 in U68 if 2 chip ROM should work. Maybe previous owner did a conversion from 6 chip rom?

Check if glue and MMU or oriented correctly in the socket. clean with IPA and reseat them.

R71 and R72 is to disable bank 2 as you stated (soldered to +5V). R60 and R61 is for bank 1. If some ram are bad you could disable bank 2 and just go with 512 Kb ram.

Get a test cartridge and connect your ST with another computer with a null modem cable and you can check the state of the computer without a screen.

It would help if you took a pic of your board and posted it here.

EDIT: Seems that you only got 512Kb ram so bank 2 is disabled or you don't have bank 2 populated with ram chips?

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Re: [ATARI 1040Stf] Not working

Postby realac0 » Sat Jul 06, 2019 5:56 pm

hi, u'r right, here image of the PCB i have.

Image

ram is totally populated.

on BLACK is highlighted what was reworked from previous owners
on GREEN what i 've worked for now
- the 4700uf CAP was not original, and was moving around not sitting solid on the PCB.
i changed it with a new one, don't care about the hot glue, i used a radial cap so i had to solder for longer legs, and secured on PCB with glue)
- i socked chips 7405 and 566 for test reset circuit that seem ok (i should check other chips for reset circuit? or is only the 7405?)
Voltages from PSU, tested on drive solder points and VCC of discrete logics seem ok (stable 5v and 12v)

About the "BLACK MARKED" of the previous owner is clear to me that:
CPU got desoldered , dunno if there was already a socket here , but 68k pins have some solder on legs. Anyway this not seem to be the problem (tested with an A500 68k, nothing change)
GLUE and MMU got for sure reworked, dunno if changed or socketed on the past. Solder points was full of flux. I've carefully reflowed pins and cleaned now seem fine
the 2 ROMS got reworked on past ... are on sockets, dunno if got changed or if are originals. Dunno if was originally on sockets or not.
the 3 resistors are clearly reworked from components side. I bet he disabled 512k ram cutting resistors legs from the top, then he soldered back from top side again.
i dunno if this was a fail on repair, or there was a success, or was an upgrade from 512 to 1Meg RAM ... i received the machine like this , not working.
Anyway on my opinion is born with full populated ram, smd solder on ram seem perfect.

on general, i've reflowed and clean from flux what was clear got reworked on past, i've clean some corrosion and tested continuity on some random pins that was reworked (for exemple i've tested continuity on all CPU pins solder side, and some address lines component side CPU. All is ok, so i am pretty confident the previous owner have not broke any trace ... at least i hope ...).
Of course, i have checked not everything, just where i've clean some corrosion and where i am pretty sure there was a rework.

SOCKETED CHIPS ARE:
the 2 roms
GLUE and MMU
CPU
U49 (the one on the center, video, or shifter i think from what i've read)
7405 and 566 (from me, that i am sure no rails lifeted, i test every pin/rail when i desolder before put the socket)

Machine is on HALT state, i have clock on Pin15 CPU but low on Pin17.
zero pulse on Addresses and Data BUS. Mostly all stuck high.
can't see nothing on video because i'am still waiting for a scart cable i've ordered, dunno if will be a blank screen or something different (i'am pretty sure will be a Blank Screen ^_^)
testing with OSC, dunno how and what i've done, happend 1 or 2 time to see on Pin17 a HIGH HALT, but after a reset back to LOW.
on 100 tests, maybe, is happend 2 times ...
pin22 CPU BERR and is always high
MFP
Pin48 (CS) is HIGH (no pulse)
Pin46 (DTACK) is HIGH (no pulse)
DMA looking for pinout from the ST schematics, i've found that:
Pin39 CLK is ok, clock
Pin38 RDY is low (no pulse)
Pin3 FCS is High (no pulse)

this is the situation ... and what i've check reading around and on service manual

if need, i can post an image on solder side too
hope for some help

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Re: [ATARI 1040Stf] Not working

Postby realac0 » Sat Jul 06, 2019 7:22 pm

About the 2 TOS ROMS, i've check code, so u can tell me if, maybe, are inverted:

C101632-002 is on LO-O (U67)
C191631-002 is on HI-O (U63)

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Re: [ATARI 1040Stf] Not working

Postby Greenious » Sun Jul 07, 2019 12:25 pm

Well, part of troubleshooting is also seeing the screen. Without a screen it's difficult to tell with confidence what's going on. It's not unheard of that MMU/GLUE connectors lose contact and you might need to straighten the pins on the chip/socket.

I assume both partnumbers begin with c101xxx otherwise they clearly not belong together.

C101631-001 = TOS 1.02 2Chip QWERTY High UK
C101632-001 = TOS 1.02 2Chip QWERTY Low UK

So that part looks correct.

As usual, https://docs.dev-docs.org/ have al the schematics, manuals etc you can wish for, but you wrote you already had schematics/service manual?
Updated my guides as of june 28th, 2016. Check'em out and feedback!
viewtopic.php?t=5040

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Re: [ATARI 1040Stf] Not working

Postby realac0 » Sun Jul 07, 2019 12:45 pm

Greenious wrote:Well, part of troubleshooting is also seeing the screen. Without a screen it's difficult to tell with confidence what's going on. It's not unheard of that MMU/GLUE connectors lose contact and you might need to straighten the pins on the chip/socket.

I assume both partnumbers begin with c101xxx otherwise they clearly not belong together.

C101631-001 = TOS 1.02 2Chip QWERTY High UK
C101632-001 = TOS 1.02 2Chip QWERTY Low UK

So that part looks correct.

As usual, https://docs.dev-docs.org/ have al the schematics, manuals etc you can wish for, but you wrote you already had schematics/service manual?


yes , of course, partnumbers begin with c101 was a typing error ;)
i agree about the screen. as soon as i have the rgb cable, i will inform what is going on screen.
and yes, i have already downloaded schematics and manual, part of the troubleshoot i've done come from there (check HALT/BERR state, clock etc.)
i'am just stuck on no activity at all on BUS and this :

my signals:
MFP
Pin48 (CS) is HIGH (no pulse)
Pin46 (DTACK) is HIGH (no pulse)
DMA looking for pinout from the ST schematics, i've found that:
Pin39 CLK is ok, clock
Pin38 RDY is low (no pulse)
Pin3 FCS is High (no pulse)

i've read around, from other posts on this forum, from a working machine:

MFP: MFPCS low pulse > DTACK high pulse
DMA: FCS high pulse > RDY low pulse

here is where i am and can't move on.
service manual say, at this point:
CPU
MFP
DMA
is the problem

i am refeeriing to this (from service manual)
--------------
----------
If still failing, the CPU is unable to read ROM or there is a component which is not responding to a read or write by the CPU, probably the MFP 68901 or DMA Controller. 'Ihe MFP should respond to an MFPCS with DTACK. 'The DMA chip should respond to FCS by asserting RDY. 'Ihere is no way to check (3) other than by elimination of the other two possiblities, although a hot CPU (too hot to touch for more than a second) strongly indicates a bad CPU
----------

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Re: [ATARI 1040Stf] Not working

Postby realac0 » Sun Jul 07, 2019 12:51 pm

Greenious wrote:....
It's not unheard of that MMU/GLUE connectors lose contact and you might need to straighten the pins on the chip/socket.
.....




how i can test this? probing each pin with logic probe?

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Re: [ATARI 1040Stf] Not working

Postby Arne » Mon Jul 08, 2019 8:31 am

Hi,
as your board has already been reworked be advised that the ServiceManual hints are based on an unmodified board.
They do not take into account that bad solder joints or cracked vias/tracks happened.
TOS (more or less all ST versions) boot with very similar code. ST Internals does include an appendix with commented code.
That way you can (at least a bit) track what is happening. I'm using a special PCB and a LA for that purpose.
Anyway: be advised that /HALT and /RESET are bi-directional signals. Get a 68000 manual and check the appropriate chapter(s).
And I can really not advise your swap & check loop behaviour! You won't find PCB cracks that way. Maybe the ST was sold after the rework didn't work?

As you will see in the ST Internal TOS boot code the 68000 will perform a Reset instruction very early.
I suggest to connect your scope to /HALT an /RESET. Trigger on Rising flank of /RESET. Switch on ST, press reset button.
On a working ST you would see on /RESET: low-high-low-high.
The second low is triggered by the reset instuction (~15µs IIRC).
/HALT should go high in conjunction with /RESET at the first transition and will stay high until push-button reset is occurring.
Check /ROM2 comming from Glue. If it is never asserted then the CPU can't fetch code from ROM. So then check all connections ROM<->CPU<->Glue.

Good luck.
Image

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Re: [ATARI 1040Stf] Not working

Postby realac0 » Mon Jul 08, 2019 9:48 am

Arne wrote:Hi,
as your board has already been reworked be advised that the ServiceManual hints are based on an unmodified board.
They do not take into account that bad solder joints or cracked vias/tracks happened.


yes, i think this is the problem.
is pretty clear that this machine already got reworked.
there is a high chance, that the guy that reworked this, failed on repair, and then sold it as untested.
i dunno if the ebay seller is the same guy, he claim have find this machine on a loft, anyway, i've buy it as "untested and for parts", so i can't complain.

is already happend to me to have a C64 like this, already reworked.
i had success on fix it, but had, basically, to desolder everything, sockets too, fix broken traces, swap lot of chips (some at randoms).
but i know pretty well how to troubleshooting CBM stuffs (on basic things), about ST i don't know nothing, and, most important, i don't have spares to tests chips or another working machine as reference.

i think i can't repair this :( :x

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Re: [ATARI 1040Stf] Not working

Postby realac0 » Tue Jul 09, 2019 10:33 am

little update:

desoldered MFP and socketed (was a PAIN, was already reworked but no socket, very very hard desolder this)
desoldered DMA and socketed
desoldered and changed the 2 sockets roms

have found no broken trace , all ok

i've broken and changed with a new one C86 (near MFP) 0,1uF extracting MFP
i've broken but i not have on stock C84 and C85 while exctracting DMA (from schematics seem 30pF caps that feed Crystal Y1 someone can confirm? on Service manual the part with components list is missing ...)

so at the moment my clock signal is no more good like before, related to the 2 caps missing i think (i hope!)

anyway, sometimes, at random, HALT is high (but at random, i don't understand if is related to some solders contact)

taking off GLUE from socket, make the HALT high 100% of times, every reset

can be a GLUE problem? there are some pins that have strange readings on oscilloscope (very very dim trace and around 2v)
GLUE have the clock, and i've check all the Address lines to CPU (A0 to A15?) and all are connected
i've try clean lot of times the socket and the pins, and reseat, never changed nothing.

can a bad GLUE give me these problems?
if yes, can someone lead me where to get a replacement? (if is worth it)

i can try to buy another 68901 too, or change roms
i have eprom programmer, and wanted to try read the eprom and compare with on line images
but i dunno which type of eproms are , about the TOS version, Greenious wrote:
C101631-001 = TOS 1.02 2Chip QWERTY High UK
C101632-001 = TOS 1.02 2Chip QWERTY Low UK
so TOS 1.02

if someone tell me what type of eproms i must use i can, maybe, burn 2 new roms with a newer version of TOS and be sure is not a rom problems (no broken traces on roms sockets)

ARNE WROTE:
---------
/HALT should go high in conjunction with /RESET at the first transition and will stay high until push-button reset is occurring.
Check /ROM2 comming from Glue. If it is never asserted then the CPU can't fetch code from ROM. So then check all connections ROM<->CPU<->Glue.
---------
i confirm HALT go high and stay high until push-button reset is occurring. then, go low ;(
if no GLUE on Socket stay high always
Last edited by realac0 on Tue Jul 09, 2019 1:10 pm, edited 2 times in total.

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Re: [ATARI 1040Stf] Not working

Postby realac0 » Tue Jul 09, 2019 1:09 pm

other update, if someone still want try help me!

rgb cable arrived, plugged in and i see a total white screen, not black.
reset seem have no effect.
but i still have to insert c84 and c85 on right place (noone confirmed me are 30pf caps, i can't find a component , so i've see only on schematics).
at the moment, looking with OSC, give me a no good clock signal (wrost than before), i hope for the 2 caps missing.

i've read somewhere that a white screen is better than a black screen ...

i've ordered another stf too, so, maybe, i can try swap GLUE/ROMS/SHIFTER.
will need to buy a MFP , because seem to be never socketed

for now, i will get today the 2 caps and put on the board, then check clock hoping is ok and retry if something different than white screen happen.
then, when i get the other 1040Stf, i will start try swapping some chips.

i've found no broken trace till now.

last thinkg is the ram. I've read this can be my problem, and that is possible bypass all for put a mod and get 4Mb RAM.
but, on these st's, is really hard understand things ... my PCB is with ram smd soldered.
witch type of ram this damn machine have?


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