Atari Mega STE trying to make to back to life

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enito
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Atari Mega STE trying to make to back to life

Postby enito » Mon Jul 25, 2011 1:57 am

Hi,

a new experience i have, i received a Mega Ste. The PSU was goosed, some caps and diodes blow, i repaired and good new life works ! now the next step and bad thing, the megaste no back to life. I connect to a SM monitor and no get nothing, black screen, the hd spin with power on but no activity (led off). I suspect something bad in the start of machine, im a little newbie in electronic, but what can be the steps for check? in the board, some test of voltages or something? Photos, yep, i put someones in flickr here:

http://www.flickr.com/photos/65389512@N ... 149168769/

This mega ste include a expansion card, is like a PC emulator or something, i removed and moved the jumper for work without expansion, and too no boot :(

I hope i can back to life, greets and thx for your time for reading,

add: I tested with SC color one monitor and i get white image, with SM black

enito

Dal
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Re: Atari Mega STE trying to make to back to life

Postby Dal » Mon Jul 25, 2011 7:31 am

First off, I've made a minor edit to your post as I really don't like to see swearing in the forums, please be careful in future ;)

Secondly, from the photos, your machine appears to be in a good clean state. As you say, that expansion card is a pc emulator - the machine should probably be run without it while you diagnose this problem. I have heard of people having problems where a psu in a MSTE has started chucking out high voltages and fried some ic's on the board. I hope this hasn't happened in your case.

First thing's first, check you have good +12 and +5 with the psu disconnected.
Then cast a beady eye over all those caps on the board - any that look suspect should be replaced.
Give all the socketed ic's a firm push
Power it up, check you still have a rock solid +12 and +5. Check that none of the ic's are getting too hot too quickly (this would indicate a fried chip - not of the McDonalds variety).

Also note that if your MSTE has tos 2.05, there is no Atari logo on startup (screen stays blank) and it takes a loooooong time to complete it's ram test before it actually boots anything. If your press space, the ram check is skipped and the machine will attempt to boot from hd or fdd.
Mega"SST" 12, MegaSTE, STE: Desktopper case, IDE interface, UltraSatan (8GB + 512Mb) + HXC floppy emulator. Plus some STE's/STFM's

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catmando
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Re: Atari Mega STE trying to make to back to life

Postby catmando » Mon Jul 25, 2011 9:10 am

Dal wrote:First off, I've made a minor edit to your post as I really don't like to see swearing in the forums, please be careful in future ;)
Ha ha 'Goosed'!
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Re: Atari Mega STE trying to make to back to life

Postby MRAtari » Tue Jul 26, 2011 8:18 am

first of all can you tell me all the parts you changed on the PSU to repair it? what parts were dead?

white screen on colour monitor is a really common problem with these machines

could be a number of things BUT i have found many times the U501 surface mounted chip right in front of the VME expansion port the legs can lift from crap solder

so you need a 10x loupe as used by watch makers etc and closely look at the legs of the chip using a pin to "lightly" see if they move

i've repaired a few like this (same issue with standard STE)

if it's not that it could be the actual chip in which case you might be stuffed as it's a custom chip to the Mega STE

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enito
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Re: Atari Mega STE trying to make to back to life

Postby enito » Tue Jul 26, 2011 12:13 pm

Hi thx for replys,

i tested all, and get a life for short time, analyzing the plcc socket of mpu was damaged, some legs are bended and tryed to fix but no more starts. I think need to remove the socket and insert new one, no nice. About PSU repair, i changed a resistor burned of 10ohms, the 4 diodes , the Q1 and Q2 and replaced the fan. The only good new the atari started for a little time, im sure is this socket goosed. I have some hot air station, i think with this i can remove the plcc socket. Hope dont destroy this jewel..

Thx guys!

:cheers:


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