Atari mega ste help

[stephen_usher]

Time to get a diagnostic cartridge and stick a terminal on the serial port?

[rubber_jonnie]

Something fairly regular with standard STs are the PLCC socket contacts. I usually remove the chip, tweak the socket contacts slightly and clean with IPA then refit the chips. I tend to do this one at a time.

I did a post on this: https://www.exxosforum.co.uk/forum/viewt ... hilit=plcc

If you are going down the route of diag cart, then make sure you use a null modem serial cable or you won't see much. I know thisfrom personal experience!!

I personally have an old laptop running Win 2000 and use Hyperterm to connect to the serial port. Be prepared for the diag cart not to work though if it isn't booting.

[Steve]

Have you removed, cleaned and replaced every pllc chip/socket?

[Tomswork]

I have removed all the socketed chips and cleaned the contacts with isopropyl. The contacts could be weak I will look in my parts pin to make the tool to work on the sockets i do have a diagnostic cartridge and null cable but we dont get that far in the startup . The mega ste came from the usa George state could have been water damaged I have cleaned it for corrosion twice once with baking soda to remove rust in some spots

Tom

[Tomswork]

Hi rubber and Steve I got the magnifing glass out and the shifter chip looks like it is sitting to one corner of the socket it can be seen abit in the pictures I will aim to work on this socket first

Tom

[Tomswork]

Here is a picture of the shifter socket pins they do appear to be out of place ignore the baking soda power I need to do a isopropyl rinse

20191211_223250.jpg

Tom

[DoG]

The socket looks fine to me on the pic provided in previous post.

[stephen_usher]

The lower set look a little dodgy, one or two not fully sprung in from the edge.

[rubber_jonnie]

I'd certainly think about tweaking them, they may look good at the top of the socket, but at the bottom where the spring part actually connects, it can be flattened or pushed in. Be careful not to tweak them too far, it doesn't need much.

Forgive the quickly and badly drawn picture, but the PLCC contact springs should look like the good one depicted:

PLCC.jpg

[Tomswork]

I have turned a old jeweler screwdriver in to a working tool will start on the weekend on that socket. The shifter ic does not sit squarely with the pins the way they.
Thank for the diagram

Tom