2.2 Booster in MegaST4

[Bikerbob]

I am fixing a megaST4 with a 2.2 booster and buffer board in it.

At least for my access the writeup on the install etc.. has been removed from the board and the store?

Is this the type of thing I could find on the wayback machine?? or is there something offline someone has?

I would like to read this, so I can attempt to fix(repair) or at least know how exactly it was supposed to be installed?

James

[Steve]

https://www.exxosforum.co.uk/atari/last ... /index.htm

[Bikerbob]

https://www.exxosforum.co.uk/atari/last ... /index.htm

hmmmm. thanks Steve, sorry I missed it, I looked for it, on the store too, was not able to find it. Thanks

James

[Bikerbob]

ok So this is the board I am trying to fix.

There is a blue diode? that has a leg lifted. but not sure I see where from? In Exxos original posts (I understand different board.. thats why Im posting) There is a R150 resistor there.. I cannot find R150 on this board.

Looking on Doc.dev - I find a 6mb PDF of the mega4 - but nothing specific on this revision. Also depending on the revision, parts marked might not be on the board. Any help.. knowing if this blue item needs to be put back in place and where the Resistor talked about is.. to be found?

"Please note these modifications were done to a MEGA ST C103277 REV2.1 board. While it is possible to fit the V2 booster and buffer board to any MEGA ST, I do not own those boards to test so likely some debugging and investigation will be needed."

16701revb.jpg

[Bikerbob]

Few more pics and question.
Was the 2.2 booster sold as a DIY project? I ask because the soldering job on this one was dodgy and dirty - I find Exxos stuff much nicer than this, but regardless I need to know if the legs lifted, joints made etc look correct because I dont see that this process of mods was discussed. Any insite?

What causes very dirty soldering? poor flux? wrong solder? I have cleaned these solder points up a LOT with ISOPROPO and tooth brush, but still had to go at it with a pick to clean all the crap off the solder joints.

What is the best way to clean that stuff up - love to hear others opinions.

boost1.jpg

boost2.jpg

boost3.jpg

[Steve]

Sometimes ppl use lead free soldering which usually gives crap results... whoever put that together wouldn't have been Exxos.. prob a customer who bought the kit previously. You could just re-flow the joins with leaded solder, but it shouldn't really make any electrical difference.

[stephen_usher]

That bottom pin highlighted hasn't been soldered at all!

I'd say lots of good (ChipQuik... I'm a new convert) flux and reflow every joint.

[Bikerbob]

That bottom pin highlighted hasn't been soldered at all!

I'd say lots of good (ChipQuik... I'm a new convert) flux and reflow every joint.

Thats why I am asking Stephen, because I believe some of this is by design.. Some of the bodge on the GAL for example is in the LAST UPGRADE.. but I am not sure.. I am also not sure where the two connecting wires goto on the Daughterboard - Exxos talks about where they connect on the Mboard.. but not the booster card.

This one was in rough shape, the buffer board had header pins put in.. not socket pins.. removing those was damaging. Fingers crossed.

[Bikerbob]

Anyone with one of these installed etc? that could show me some pics? This is the motherboard I am installing it on. So getting it by the PSU is going to be an issue. I think I will elongate the holes on the PSU pcb and shift it over to the right a smidge.. won't affect anything as this machine does not use its shield anymore.

James

megastb.jpg

[Steve]

Apparently:

R150 is a resistor in the 16mhz line from the shifter.

So perhaps you could buzz-out with your multi meter onto resistors in that area, with the other end of the meter connected to the 16mhz line on the shifter... that might help you find it probably.