Faulty Falcon

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Atari freak
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Re: Faulty Falcon

Postby Linuxbuilders » Tue Jun 15, 2010 1:08 pm

checked and that is what happens:

mfpint is strobing, mfp pin 8 is around 250khz
bg,br are high no strobes, nothing holds bg/br lines down
as,lds,uds,rxw are strobing
rom2 is strobing
rom3,4 is high

I will order new combel and mpu just in case as spares and replace mpu first.


quick question - is it possible that my real time clock does it? I have new chip in there but there is always possible that it is faulty.
I have found out in here that some guys had similar problems with faulty/not soldered well chip. What would be obvious symptoms on the circuit if nvram is dead or not in place? Would it affect testing cartridge operation? thnx
In hell we will meet again...

simbo

Re: Faulty Falcon

Postby simbo » Sat Jun 19, 2010 6:18 pm

replace the rtc anyway
check all its com lines to there points on ic's
to be sure no embeded i/os are dis.,..
in other posts people have cured this self generated problem
ic's CUT them off
heat and REMOVE the pins
suck out the solder...
replace
or you most often damage the thru's to middle layers

you never know ,.. but why did the reset chip fail??

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Re: Faulty Falcon

Postby Linuxbuilders » Sun Jun 20, 2010 6:59 am

RTC looks good, all lines are healthy. Chip is new, I have reconditioned my old chip, some story, it is not that.
I have replaced mpu and combel. What I get now is a bit different. First it reboots as before (ticking) but after a while (few secs) it stops and the screen gets funny lines or it starts flickering it and then stops on white with some dots. Then when I reset it the clock gets 8MHz and does not switch back to 16. So there is somewhere else a problem. I have got new coprocessor and this one works, no problems here - no hanging when in the socket. Cartridge still hangs whole device. I am thinking that it may be something what is initiated in first steps of boot form cartridge. If cartridge kills whole device then there is two options, one is that it tries to execute ram or other thing and gets stuck on this part or the cartridge is faulty (what I am not sure about). Now way to check. Hard case :(

Lastest findings: Each tick XMFPinit goes down and IO1,2 are down. I think it will be the 6850 Which I took out of my 520ST - replaced but no change.

Took out 68901, not tha, so not many choices left, ether VIDEL or DMA, I bet VIDEL. Without DE it is still doing odd things on the screen.
Videl out and resetting stops. Clock is 16MHz.


http://www.youtube.com/watch?v=10FSi4ZI-9o
http://www.youtube.com/watch?v=42zehoy4WK0
http://www.youtube.com/watch?v=8gxOjqTmMS8
In hell we will meet again...

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Atari freak
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Re: Faulty Falcon

Postby Linuxbuilders » Tue Jun 29, 2010 9:26 am

New update, I have got new/old working Falcon and when I have tested it with my diag cartridge I have found why my faulty one dies when cartridge is in. It (cartridge) is instantly requesting video, because my VIDEL is dead (I would say even more, it is shorting bus during init) then the whole thing is crashing. This is d problem, I think testing cartridge should work in different way. I would not initiate VIDEO and other chips at all, I would do RS232 first and then from this level execute chip by chip initiation. Then it would be possible to pick up faulty part of the circuit. Perhaps software guru challenge... :), I have tested my ram and it is healthy so this is a good news. If I am lucky VIDEL replacement will fix it.

So as it goes I have brand new 4MB card for sale if anyone interested :) This one was purchased as spare from myatari (was meant to replace the old one - now not needed anymore).
In hell we will meet again...

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Re: Faulty Falcon

Postby Linuxbuilders » Fri Oct 08, 2010 8:59 am

hi,
After a while I have got a time to look at it again, the ticking sound from speaker and reset going signal crazy is GAL problem - U67 if faulty and doing this. I have replaced it with GAL from my working falcon and I have the unit responding.

The unit is freezing when IDE tries to reset, so far I have replaced following chips - VIDEL, MPU, COMBEL, U24, U33, DMA, U42,U43, fixed reset circuit, U67, RTC

Here are pics from cartridge tests, it starts when is first powered on, after manual (push button) reset the unit is not responding...I have specifically looked at chips for tiny particles of copper, solder, etc but chips are clean.

IMG_0931.JPG

IMG_0928.JPG

IMG_0929.JPG


proper behavior is:
as blue screen but after IDE is reseted program kicks on OK and brings up testing menu.

Suggestions?
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In hell we will meet again...

simbo

Re: Faulty Falcon

Postby simbo » Fri Oct 08, 2010 8:56 pm

something is not right around u25 inverter and issue with the solders at u24 or the 68901

try these places
on the schematic u25 is an inverter stick a scope around this and pin 1 2 3 4 of the 68901

is the signal CLK4 avalible at the 68901

T0 mfp

says in the service guide that its
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Re: Faulty Falcon

Postby Linuxbuilders » Sat Oct 09, 2010 4:45 am

u24 one leg, combel one leg, all is flying like a baby now. :)
So now I need to get fpu and GAL-U67 and all can be put together back as it was.

thnx for help
In hell we will meet again...

simbo

Re: Faulty Falcon

Postby simbo » Sat Oct 09, 2010 7:02 pm

yipeee!!! :P

didnt i give you the url of gal listings just make one
im sure i can program a 67 for you

i have that jed and a programmer for the chip
just need a blank

fpu i posted a link to a hoarder selling them in the states for £13 inc post international

its a few topics down


just to add that in this post viewtopic.php?p=167064#p167064

i added that your better using a cart and a serial cable !!!! first

it can show a simple error

but we both know that this fault was maybe someone plugged it into 240v thru the midi
or a stage midi error with 5 din etc etc
as it was that buffer chip for reset and midi buffering was defo fried and can have a bad transiants effect on the whole chipset

i think adding some clamp diodes and esd circuit to the midi ports could have saved it from frying
perhaps a mod people would wish to have

retro computer midi i/o buffer

a simple box to protect your retro pc from harm

there is a project for someone

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Re: Faulty Falcon

Postby Linuxbuilders » Sun Oct 10, 2010 12:17 am

GAL kills the whole machine, no didly dong from it. So you need good GAL to get it responding. Reset circuit was bad too, FPU, MPU, Combel was cooked so there was quite a damage. So step by step after replacing whole machine it got up. I have got clear nail polish to paint chips and all will be great from now. :)

Catch me up on Skype and we talk about GAL, fpu I get from ebay as u said. I have got a big bag of sims and edo so if you need any you know where to look.
I have DMA and VIDEL from this box, I think they are good just second hand, plus I have some other brand new chips I have never put into this one so if you need some parts call me man.

Thnx Bro.
In hell we will meet again...

simbo

Re: Faulty Falcon

Postby simbo » Sun Oct 10, 2010 3:57 pm

kool

now i really need to spend more time with bonus machine fix the remaining error
will be a daft pin for sure

ill try to be online on tuesday life stuff and work

i may need a dma is one is avalible ... i do for this other bonus pcb

ill catch you tues morning for a chat on skype

ciao fr nu


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