Macintosh Classic Help and ROM removal

[tonikoche]

I picked up a Macintosh Classic knowing it was non functioning for a very nice price. It has horizontal lines across the screen on start up with no bong. When turned off and on a few times its horizontal lines are scrambled into a mess. It needs a new PRAM battery. Will it boot without the PRAM battery? 

My guess is it is the capacitors. I've had the motherboard out to lightly rub the areas around the capacitors with methylated spirits. It had a very little amount of capacitor liquid on the board. It seems to have not done much damage and the motherboard is in very good condition. I would like to know how to remove the ROM chip so I could wash it. 

Thanks

 

[Paralel]

It will boot without the PRAM battery, no problem. You can just pop the ROM chips up with a small screwdriver from one end at a time and then just pull them straight up to prevent bending any pins.

 

[tonikoche]

Thanks a lot. 

After I took it off, I noticed there is an extra set of holes at one end. What are these for when the ROM chip can't even fit all their pins in the extra holes? 

 

[tonikoche]

When it first boots I get these horizontal lines.

After I switch it off and on I get this jumbled mess.

 I plan on putting it through the dishwasher tomorrow. I've already scrubbed the area around the capacitors with alcohol with no success. A full re cap will be attempted after I get the parts.

Any help would be very helpful.

 

[Elfen]

It will need a full recap to at least perhaps getting it started.

During the recap, check the area with the removed cap with a magnifying glass and check if the traces are intact. Then with a multimeter check the trace from end to end. Also check for corrosion  where the trace goes to a chip, you may have to resolder those areas. If you are lucky it should come up with just the recap alone.

When you remove the solder, I found that adding solder to the trace make it melt faster and easy to pick up with a dsoldering wick or dsoldering iron. Clean up the trace with acetone and Q-tips (cotton swabs in the UK). Check out Ferrix97's video on removing caps from the board, I find that unless the corrosion is really bad, it saves traces. Here's the link: https://68kmla.org/forums/index.php?/topic/23469-macintosh-lc-restoration-video-series/?p=243442

My Classic II came back from a dead point like this to fully booting, but there is no sound so I have to check some traces.

Good luck with that. Hope it goes well for you.

 

[bibilit]

After I took it off, I noticed there is an extra set of holes at one end. What are these for when the ROM chip can't even fit all their pins in the extra holes? 

Yes nothing unusual here, mine has those extra holes too.

 

[sadmanonatrain]

You should also make sure that the capacitors on the analog board are not leaking. They are worthwhile replacing! 

 

[tonikoche]

Thanks a lot everyone. It is worth it to still put it through the dishwasher before the recap? 

 

[Macdrone]

I do

 

[tonikoche]

So I've washed the board twice. Once with a little bit of dish liquid. I still get the small thin horizontal lines. Yes, I will need to get it recapped. Although shouldn't it function now that I've wiped the very small amount of capacitor liquid off the board?

I get the checkerboard pattern when I attach the RAM expansion card without the two extra RAM cards installed in the extension card. Yes, I switched the card to "No SIMMs installed'.

Do any of you know what is wrong?  

 

[Elfen]

It needs a recap, nothing is going to improve until that gets done first. Washing the board got rid of the corrosive cap crap. Now you need to check with a high powered magnifying glass to visually check the traces and see if any of the cap crap broke any. Looks can be deceiving as traces can be broken under the caps or a chip. You won't know that until you start doing the recap. But at least the trace can be followed from end to end and wired up if it is broken.

 

[techknight]

its also possible you have rotten traces, it depends on how bad the board looks around the capacitors. 

 

[bibilit]

last but not least, you may have or not a bad A / board (maybe not supplying the right voltage)

Can you have a look at the 12v / 5 v supplied ?

 

[tonikoche]

Can I test the voltage through the external floppy drive port? If so, which pins are 5v and 12v?

 

[mfaircloth]

I  need to replace the 40 pin rom on my mac classic, what eprom type do I need to use?