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Mu0n

LCIII battery 'splosion

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I always tell people to remove batteries ASAP and resist using them ad nauseum. 

 

 

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I opened up my LCIII this morning with the goal of seeing if it had these SMT caps that I would replace with tantalums, just like I did for my SE/30 and Mac Classic (yep it does). Lo and behold, the battery had been left in and was exploded.

I half-heartedly submerged it in soapy water to see if I would go on wih a restoration or not, so I didn't take before pics. Fortunately, the worst area was near the HD cable (which I wasn't using, this machine had no internal HD) and it went away for the most part with no affected trace in that vicinity.

 

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As you can see, the single RAM SIMM has one side with heavy corrosion, but with enough brushing w/ IPA, and then a bit of slow and deliberate nose-plier scratching, I think its leads create a good contact, pin per pin, with its socket. Who knows before booting, right?

 

This is after a first pass with light steel brush.

 

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One of the ROM chips has lost one of its legs in the chip socket. I have an EEPROM burner, I've done the whole HI/LO separation with the software for a Mac Plus, but I don't own 40 pins empty EEPROM. Initial searches aren't making me optimist at finding an new IC for this. Any pointers?

 

 

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All in all, the restoration looks doable. The most damaged area (the empty gray socket in the center which I assume is for a math coprocessor?) has a couple of eaten away leads inside it and the HD connector is damaged on the other side of the board - but I wasn't planning on using it anyway. All I need to do is to put in some tantalums and deal with the ROM chip and hope for the best.

 

All in all, if one of my machines had to give up the ghost, it was this one. It's the one I'm least attached to, but it would still be a bummer if I lost it - it's the only old Mac that gives me access to color! I had plans to trade it out eventually though. I can live with emulators for my color access.

 

 

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Carefully file down the chip package to expose the internal trace where the leg did break.

You can solder a new leg to that trace if it didn’t corrode internally.

 

I will have to look at the schematics but you might get away with a 42 pin EPROM like a 27C160 as a replacement.

Edited by Bolle

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8 hours ago, Bolle said:

Carefully file down the chip package to expose the internal trace where the leg did break.

You can solder a new leg to that trace if it didn’t corrode internally.

 

I will have to look at the schematics but you might get away with a 42 pin EPROM like a 27C160 as a replacement.

I found this: https://l.facebook.com/l.php?u=https%3A%2F%2Fwww.newark.com%2Fmicrochip%2Fat27c4096-90pu%2Fone-time-programmable-otp-eprom%2Fdp%2F68T4285%3Ffbclid%3DIwAR36vSFRAWv1CFKjT4qBZAbBZDC_VsLyh43BzG6CGHq4IXDUZVbV2KggB9Q&h=AT21QIRd0wPho2SCqDAu5YW33lRXazlHhBq7lJVLorKcUyoUOhNNyTS3OmN3RozDHn5BcEcRxbwgGby_FvCzvGvnnC0Pqlg6hvyMqVEE3C9EFNtQaFSIO13ygERm8YCJuA&__tn__=R]-R&c[0]=AT2V_LZrMcZD0hiZh5qhwtm5uDrG4toQqZeTEAlUhI9vF4No76TRSxT6BFjerPDcGXVUcJCwsXEUU_ltI5X5IgJb4DXd2fLRMsCOp3WYbi5wERi1NIZWEHfWx1n9PoBllwVr7MwWv1YNpY1bDy4fkrhN5-8yfYEX6_sww-GxyPKwFVcfDK7cIs4

 

but, I don't have an UV EPROM burner. I only have the popular TL866 EEPROM burner everyone has, and a bunch of W27C512-45Z DIP28, which were perfect for a Mac Plus. So one chance at it and pray I didn't mess up the HI and LO separation?

 

 

Edited by Mu0n

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I'm trying to remember the steps. Is that how you load each half of the 1 MB LCIII rom file (2nd and 3rd pull-down menu options)

 

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That looks correct to me

 

I wrote a program to split rom files for me in the past, never thought to look for a option to do it in the minipro software, I'm kinda annoyed at how much time I wasted doing that now.... oh well at least it worked :)

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Ok, this is not making me confident. I tried reading off of one of my Lciii Roms (the least damaged one) and I went through all the 40 pin chips supported by the Xgpro software. My first choice was in the ATMEL section, but the software complained that the pins didn't match. I did not make an error with the notch. About 80% of the other choices had the same error. The few models that did allow me to get a read going yielded almost all FFFF bytes, except in a few places where it showed up at FF8F. 

 

What am I doing wrong and is this just plain not supported? Has no one reburned lciii Rom chips here? 

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That software can read old unknown ROMs?  Last time I tried I wasn't able to make it work either, trying to read a ROM out of some old 6502-based terminal I was messing with.  For that thing I ended up just wiring up a microcontroller I had laying around.

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11 hours ago, tattar8 said:

That software can read old unknown ROMs?  Last time I tried I wasn't able to make it work either, trying to read a ROM out of some old 6502-based terminal I was messing with.  For that thing I ended up just wiring up a microcontroller I had laying around.

Your question confuses me even more. How am I supposed to write + verify a replacement chip if it can't read that type of chip? Or are you implying that reading off an old chip is a totally independent thing than the verification step after writing to a new chip? 

 

Which begs the question, is the choice of which new chip I can buy and write to extremely narrow or can many choices work? 

 

 

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I got 4 OTP ICs in the mail (AT27C1024) and burned one of them with the high byte of every word, but I think I have a much larger problem now

 

1) I wanted to solder legs 11 and 12 of the U36 chip on the back of the logic board but I don't think I have a trace to grab onto. I used a schematic I found but am not 100% certain of where these specific pins lead. Some of them are easy (ground) or go to the big SCSI connector pins and work well. ( I can provide the pdf if you want)

 

2) I still tried to smoke test it despite that, without a battery replacement and I may or may not have smelled a very slight burning smell (I'm only 30% sure). I hear the disk drive move a little, no bong.

 

3) I tried plugging in the 2 monitors I have (a small 12 inch monochrome and a 14 inch color), which both power on, but remain pitch black (uh oh). I haven't used these in like 14 years easy.

 

does the LCIII require a pram battery to attempt booting? I don't remember.

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