exxos's Atari, Amiga & retro forum

rubber_jonnie wrote: 05 Aug 2020 23:43 I've checked the datasheets and everything seems the same:

You have things so easy :lol:

exxos wrote: 05 Aug 2020 23:58

rubber_jonnie wrote: 05 Aug 2020 23:43 I've checked the datasheets and everything seems the same:

You have things so easy :lol:

Nice to have something go my way on this one!!

Tried reading the original ROM, but it is a no go, so I think it is dead, as the 27C400s I have, being the same pinout, read just fine.

So so far looking like a dead CPU and dead ROM since all the voltages measure correct at the power plug in the mobo.

On a positive note, a guy over at the 68kMLA forum has offered to send me some boards for spares that were killed by the affectionately named 'Maxell Bomb'.

It's called this when the PRAM battery literally explodes over the mobo and corrodes things beyond the point of no return.

Given my board seems to be ok from a corrosion PoV, it will at least give me other chips to work with if I need them once the CPU is replaced. Just waiting for a CPU socket now as well, we'll see what occurs after that.

@rubber_jonnie

That's good to hear about some spare parts and I have seen those battery pop got to love lithium batterys of any type. Those are in the mega ste as well

Tom

Tomswork wrote: 06 Aug 2020 15:21 @rubber_jonnie

That's good to hear about some spare parts and I have seen those battery pop got to love lithium batterys of any type. Those are in the mega ste as well

Tom

Yeah, the parts are good news indeed.

I have removed the battery from my Mega STE, as I have a CosmosEx it sets the time at boot, so there's no requirement for a clock battery :)

As promised, I've posted a list of the analog board capacitors I swapped in my other thread, but for consistency it's here too:

The list of analog board capacitors for my particular Mac Classic as follows:

2200uF 16v
1000uF 16v
1000uF 10v
47uF 25v x2
2200uF 10v x2
470uF 50v
RIFA PME 290 MB or equivalent. I believe the value is 10nF, but check your values.

In addition I replaced 7x 47uF 16v and 1x 1uF 16v capacitors on the logic board with tantalums.

Again, check your own board first for values and quantities.

I've also managed today to get the socket installed:


And I went with the suggestion from @Tomswork to remove the plastic square from the middle of the socket to get access to the centre of the socket to allow easy access after the hot air solder so I could clean up.

Obviously I will need to drop the plastic square into the bottom of the newly installed socket to ensure the chip sits in the correct spot.

As it happened there were only 3 solder bridges and all cleaned up fine with solder wick. Continuity is all fine and I have checked for shorts too, and all is fine there too.

I have a spare ROMs now, so I can test as much as I like, but need to make sure the ROM is correctly placed in the socket to avoid killing another.

Next I need to power up ROM and CPU less to make sure all seems well in terms of power at the pins.

Looks good i was digging thru my macintosh box down in storage and found a mac classic board it has some issues. Nice work on the socket

@rubber_jonnie

Tom

@rubber_jonnie

Can you see why this classic board does not work
Tom

Ooops! :-)

Tomswork wrote: 29 Aug 2020 19:22 @rubber_jonnie

Can you see why this classic board does not work

20200827_231107.jpg

Tom

Yup, that'll never fly right!