68kMLA Classic Interface

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Trying to repair a Classic II
Posted by: bibilit on 2016-08-11 08:15:38 One question: The white plastic that covers the solder side of the Analog Board, How is it removed? by removing the black rivet like pins. Push the center of the pin on the opposite side of the domed head (so pushing from inside out) then remove the complete unit, on reversal, push the center pin towards the domed head, and the pin will be locked into place.
Posted by: SlateBlue on 2016-08-11 19:12:15 Nice discharge tool, by the way!
Posted by: GroovyDrifter on 2016-08-13 06:11:34 Thank you! I'll try to remove the analog board this saturday and if all goes ok next week will do the fix.
Posted by: GroovyDrifter on 2016-08-17 01:23:15 Finally I removed the board monday, instead of saturday... we had to deal at home with an issue with one vitro ceramic hob and that gone first (it burn itself). Anyway monday was holydays here so no problem at all. I did found a floppy stuck inside the drive. The CRT was already discharged, I heard nothing when apllied the discharging tool, but having it gave me the confidence to continue. All I did was following Apple service manuals, so easy. I decided to clean the plastic housing, so I completely removed all the parts. The case after the cleaning. Part of the yellowing was dirt, but it could use a retrobright too. I choosed to not do it and keep the apple sticker attached. After reassembling it, except for the analog board. I cleaned all the metal parts and re-greased the floppy drive. Some photos of the analog board... almost all the capacitors on the output side of the power supply are damaged, the rest look good, but will be replaced anyway. Most of the power transistors and regulators, and the optocoupler will be replaced too. The replacement parts are on their way, but they're taking longer than usual. TME has sent their parcel but RS has just sent the thermal silicon grease, none of the capacitors... 🙁 I've choosen longest life, lowest leakage current (low ESR), 105ºC capacitors, wich in almost every case leaded me to a Rubycon capacitor. And they are not cheap. Most of them are smaller than the original ones, maybe It's a good idea hot-glue some of them. The optocoupler finally was a CNY17G-3, so either the Analog board was replaced by a Classic one at some point or it was also a factory option for the Classic II Being a switching power supply it was quite surprising to find a linear regulator. It may be still good but I've bought a Double Gauge replacement and hight thermal conductivity silicon grease. It has two unipolar mosfets, I suppose one is for the Power Supply and the other for CRT. There are two parts that I've not found new, best option I've found were new old stock in ebay: the TDA4605 and the TEA2037A. I'll keep them unchanged. Have you ever had a problem with those two parts?
Posted by: GroovyDrifter on 2016-08-18 16:41:55 Hi! This morning my last parts arrived so after work I've spent my afternoon replacing components in the analog board. I first started replacing the power transistors, rectifier bridge, that big diode near the transformer, regulator and optoisolator. Well... it really gone first the big cap at the input side of the power supply, 🙂 Then all these electrolytic capacitors were waitng to replace those in the board Hey,-ho... let's go! Some hours later the field was full of the dead bodies of all those capacitors that gave ther lives in the hot guts of this compact Mac. May them rest in peace(s). Following some views of the field of glory, with those new components that replaced their old mates waiting to hear the call of duty... or should I say the power-on chime? Should I add tho that a "REBUILT IN SPAIN"? But wait... will it work?.... YES!
Posted by: Elfen on 2016-08-18 17:47:28 Congrats!!!
Posted by: SlateBlue on 2016-08-18 18:02:53 Glad you got it fixed!
Posted by: bibilit on 2016-08-18 22:37:15 Congrats.
Posted by: GroovyDrifter on 2016-08-23 13:25:12 Thanks guys for your help and support! I've done a little video and uploaded it to my youtube channel, nothing fancy but anyway I link it here in case you want to watch it... Next on the list a very weird acting SE/30, I'll open a thread soon.
Posted by: Elfen on 2016-08-23 18:11:59 Talk to Paralel and 360Alaska about their Classic II FPU Card they designed and built. A nice machine like that should have one. https://68kmla.org/forums/index.php?/topic/23149-classic-ii-fpurom-card/page-3&do=findComment&comment=284460
Posted by: GroovyDrifter on 2017-05-23 11:39:50 Hi! Sorry for refloating this old thread but that Classic II I recapped has developed a new issue... I f you use it for a short time, all is ok, but when you left it on for a long time (several hours) the screen brightnes increases A LOT, I mean, it goes almost completely white. If I adjust it then, all looks ok, but then what happens is that when the computer is cold or off for a long time, the image is very dark. Any ideas what is happening?
Posted by: techknight on 2017-05-23 13:44:30 you have a transistor that is drifting with heat. The only way to snuff that out is with freeze spray, or a pin-point heatgun. Youll find the faulty semiconductor really quickly.
Posted by: GroovyDrifter on 2017-05-23 16:09:29 Thanks, that's a good idea, I replaced all the bigger semiconductors but maybe I got one defective or the termal grease was not good enough
Posted by: techknight on 2017-05-24 15:08:48 its usually the little small signal transistors, and diodes that do this.
Posted by: GroovyDrifter on 2017-05-30 14:31:50 Thanks again, those I didn't change then, I'll try to find the bad one but this time I'll change all I can identify. I imagine that the closest to a hot part (those near a dissipator) are more probable suspects. Off topic-> I never get email notifications whenever there is a new post, Is there a problem with gmail accounts like mine?
Posted by: BadGoldEagle on 2017-05-30 15:18:55 Email notifications are broken for now since the last hosting move... It's not only you but everyone who's concerned. The admins are working on it.
Posted by: GroovyDrifter on 2018-06-24 12:14:54 I had no opportunity of changing anything, I've been "fighting" depression for some months, but I'm much better now. Anyway, a friend of mine sent me a Classic Logic Board for re-cap (checkered board screen) an as I have no Classic had to open my Classic 2 to do the tests. After this months the computer refused to start, at first there was not even power on gong or any image at all. After checking I realized the Analog board was outputing 4.5V and -11V. I adjusted PP1 and all went ok, but as It happened after month without being powered, I wonder If this and the 0.2V AC component of the DC outputs, the change in screen brighnets, all togheter can point to any defective component, can´t it?
Posted by: jshardin on 2022-10-25 19:25:06 Finally I removed the board monday, instead of saturday... we had to deal at home with an issue with one vitro ceramic hob and that gone first (it burn itself). Anyway monday was holydays here so no problem at all. I did found a floppy stuck inside the drive. View attachment 4451 The CRT was already discharged, I heard nothing when apllied the discharging tool, but having it gave me the confidence to continue. All I did was following Apple service manuals, so easy. View attachment 4450 I decided to clean the plastic housing, so I completely removed all the parts. View attachment 4436 View attachment 4438 View attachment 4439 The case after the cleaning. Part of the yellowing was dirt, but it could use a retrobright too. I choosed to not do it and keep the apple sticker attached. View attachment 4437 After reassembling it, except for the analog board. I cleaned all the metal parts and re-greased the floppy drive. View attachment 4440 Some photos of the analog board... almost all the capacitors on the output side of the power supply are damaged, the rest look good, but will be replaced anyway. Most of the power transistors and regulators, and the optocoupler will be replaced too. The replacement parts are on their way, but they're taking longer than usual. TME has sent their parcel but RS has just sent the thermal silicon grease, none of the capacitors... 🙁 I've choosen longest life, lowest leakage current (low ESR), 105ºC capacitors, wich in almost every case leaded me to a Rubycon capacitor. And they are not cheap. Most of them are smaller than the original ones, maybe It's a good idea hot-glue some of them. View attachment 4441 View attachment 4442 View attachment 4443 View attachment 4444 View attachment 4445 View attachment 4446 View attachment 4447 The optocoupler finally was a CNY17G-3, so either the Analog board was replaced by a Classic one at some point or it was also a factory option for the Classic II View attachment 4448 View attachment 4449 Being a switching power supply it was quite surprising to find a linear regulator. It may be still good but I've bought a Double Gauge replacement and hight thermal conductivity silicon grease. It has two unipolar mosfets, I suppose one is for the Power Supply and the other for CRT. There are two parts that I've not found new, best option I've found were new old stock in ebay: the TDA4605 and the TEA2037A. I'll keep them unchanged. Have you ever had a problem with those two parts? I too was surprised to see linear regulators as well.. Has anyone looked at replacing them with something like a traco equivalent? I just opened mine up and am not familiar with these analog boards at all, so I may just be talking gibberish at this point, but given the heat problems with these compact macs I would be interested in anything that could be used to remove heat (and inefficiency) out of the power circuit. Do you have a part number for your mosfet replacement mentioned above? My board is in similar condition with corrosion around the regulator pins.
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