Hello,
I have a Mac IIx that needs some help. Oh, I am new to mac II's
I have learned about jump starting the machine with a dead battery. I get no bong, no sound at all. Not surprising as seveal smd caps look bad. I can replace those.
But I see corrosion around the pictured item. I do nto know what it is. Can one of you mac experts help me identify this part and recommed a replacement. Location Y4.
The MB is a 820-0228A.
Also is there anything else I should be looking closer at. Tip and trick for fixing these systems.
Many thanks
Thanks
Looks like a leady radial capacitor, but what I find "Y" parts are is "crystal, magnetostriction oscillator". If you're lucky most of that will clean up. If not you may have to repair some broken traces. Sadly from what I've heard that kind of damage from leaky caps is the rule rather than exception for that era Mac. Anyway, if you can get that thing out and check the markings, whatever value it is should be marked somehow. Most crystals are sort of rectangular shaped, but this one is cylindrical.
Definitely a crystal for the Sound Chip. If similar to the SE/30, it would be 16.9344 MHz. Weird that there would be "corrosion" around that. Perhaps leakage from C21?
Looks exactly like rosin flux residue corrosion to me.
One of the more common packages for PZT crystals. Corrosion starts from leaked electrolyte from C21, and travels over the surface until it meets metal it can attack (traces are protected by soldermask).
The electrical connection is probably still good until the plating of the leads gets eaten off. Remove the leaking SMDs, neutralize electrolyte with baking soda, wash thoroughly, and then see if anything needs to be done for the crystal. Covering the area with sticky flux and "scrubbing" with a hot iron loaded with solder should clean it up without removal.
Many thanks everyone.
I will be recaping the whole board when the parts arrive.
I have never seen corrosion like this before.
I just tested C21 with my in-circut DCR/ESR analyzer and the cap tested good. There is no obvious signs of cap buldge ot leaking. The cap solder pads are a little dull, but not like C12 in the new pic attached. Plus the Y4 corrosion easily wiped off, unlike the cap corrosion of the obviously leaking cap at C12. (hard to see in the pic, but C12 is bulging to the right and sitting off level )
Do these crystals go bad? If so, would it prevent the system boot bong from sounding when I jump start the board?
Again I much appreciate all the help.
DSCN6994.JPG
The issue with these era SMD electrolytics is that they are pretty much all going to leak. If you see any dullness on the solder pads it has already begun. Dull solder is not normal on leaded solder fillets (as opposed to lead-free alloys that are dull to begin with).
The crystal itself could also be bad; sometimes this can be diagnosed by measuring capacitance.
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Thanks.
Looking at other SMD caps on this board, I can see that there are several with no corosion next to them, but components near them are show corrosion. Just like what is shown in the first picture. So as mentioned above, again thanks, corrosion must travel under the mask to other compnents.
So After removing the SMD caps, I will have to beep test a lot of traces! Not looking forward to that.
Again thanks everyone!