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| Classic II recap woes part 1 (bars + static noise coming from speaker) |
Posted by: JRL on 2020-06-16 18:56:58
So I have 3 Classic IIs now, and all of them have issues post a recap of analog and logic boards.
The first one (before I removed the EGRET chip and cleaned underneath it) would do the following:
1) Bars - sometimes if I flicked the switch off/on rapidly at this stage it would boot up successfully
2) Blank screen
3) (very rarely) boot up
Post EGRET removal/cleaning, it always boots up to the bar screen (the exact same one that it displayed in outcome 1) and flicking the switch does nothing). After 10-15 seconds, I also hear varying levels of static noise from the speaker.
I'll drop some more pictures of the board, but in the meantime this board exhibits the same behavior on all of my Classic IIs as well as my Classic I, so I'm 100% sure it's an LB problem. Reseating ROM and removing the installed RAM hasn't done much. My Classic I board also works great installed in the Classic IIs.
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Posted by: JRL on 2020-06-16 20:21:45
I was thinking I may have introduced additional contamination to the EGRET (thereby causing the weird static noise-I used chipquik and flux to remove it and hot air to reattach) - if so what would be the best way to clean it? Would immersing + scrubbing with IPA/DI water work?
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Posted by: bibilit on 2020-06-16 23:18:51
The Egret should be cleaned properly on both sides (logic board and chip itself) not an easy process, sometimes heating again after adding fresh solder on all the legs is the way to go.
Also, there is a small chip nearby to remove, clean and refit as well.
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Posted by: superjer2000 on 2020-06-16 23:59:03
How are the voltages? I love ChipQuik for removing SMD and through-hole components but I take care to wipe my soldering iron off on a different sponge or paper towel when using it so I don't contaminate my wire sponge with it when I'm resoldering items back on after. I'm pretty sure the ChipQuik solder mixed in with regular solder wouldn't make a good joint.
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Posted by: JRL on 2020-06-17 04:28:20
The Egret should be cleaned properly on both sides (logic board and chip itself) not an easy process, sometimes heating again after adding fresh solder on all the legs is the way to go.
Also, there is a small chip nearby to remove, clean and refit as well. Hey, sounds good. I will re-remove/clean again. But I did originally clean both the logic board and chip itself on both sides, as well as add fresh solder on both legs. If the small chip you are talking about is U11, I removed/cleaned that.
How are the voltages? I love ChipQuik for removing SMD and through-hole components but I take care to wipe my soldering iron off on a different sponge or paper towel when using it so I don't contaminate my wire sponge with it when I'm resoldering items back on after. I'm pretty sure the ChipQuik solder mixed in with regular solder wouldn't make a good joint. Voltages seemed to be very slightly under but I'll recheck them again. And that's good advice, I tried to use fresh normal solder on each pin after cleaning pads. I'll try and be a bit more careful when i do this the second time.
I just hope I didn't fry the EGRET...
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Posted by: techknight on 2020-06-17 05:34:37
I am not sure what you would have done to fry the EGRET. I would have to pull a schematic to see what all the EGRET does in the classic. Not sure if it handles audio at all. But I think its an HC05 or HC08 based IC, and if the ROM is known, a new one could be programmed?
a little bit of chipquik mixing in with fresh solder during reflow wont hurt anything. ive done it before, although I haven't used chipquik in a very long time though.
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Posted by: techknight on 2020-06-17 05:46:33
So here is a CPP code module that basically explains how EGRET works:
https://git.redump.net/mame/tree/src/mame/machine/egret.cpp?id=57eeffb661c0fd6ef6e20e1b08d8ddb6e5a0ae17
And, if you hunt around on google, you can find the ROM dump of the EGRET. So in theory, it is possible to find a NOS 68HC05 that matches in pinout, and maybe OTP program the ROM.
And with this, if you dig deeper, you may be able to find more code that emulates the functions of some of apples chips, which could be used to re-create some of the old Apple chips on clones such as a new SE/30 board with GLU programmed in a CPLD.
But I digress.
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Posted by: JRL on 2020-06-17 05:50:09
That's awesome! I'm hoping that I just didn't clean the EGRET enough... but I'll report back.
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Posted by: joshc on 2021-01-18 00:39:25
That's awesome! I'm hoping that I just didn't clean the EGRET enough... but I'll report back. What happened with this? Did you have any luck after cleaning the EGRET?
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