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Macintosh Classic II Questions

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Hello everyone,

 

I bought a Macintosh Classic II in really nice condition on eBay. Cosmetically from the pictures, I rate it as an 8/10 with hardly any yellowing, including the keyboard and mouse. I haven't received it yet, but I plan on restoring it to a working state. The seller said the computer turns on, but there is no startup chime and nothing comes up on the display, although the fan runs. I've heard the capacitors can be a culprit. Does anyone know what would be causing these symptoms? I figure either something is disconnected internally or there is another problem at hand. I would imagine the power supply is okay if it turns on.

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Not too much else to speculate on until it arrives.  It does sound like there is something disconnected, but as you also noted, there will need to be recapping. Good luck and let us know how it turns out

Edited by Juror22

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The problem with pre-reciept posts is the crystal ball effect. Nobody knows! we could speculate until the sun goes dwarf but ya know... 

 

But what I CAN tell you is at this point the logic board needs recapped, and thats only if it didnt have a maxell battery that exploded all over the inside of it. 

 

Thats my speculation. First part isnt, second part is. 

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logic board will need cleaning, capacitors replaced.  If the battery has not exploded it should be pretty repairable.  Same as the classic in that way.

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It's got some work to do. I already know that. I sure hope the battery didn't explode. I won't know until I get it, though. It says it was manufactured in November 1992, and I read somewhere there were two revisions of the Macintosh Classic II regarding the logic board. I'm thinking this is a Revision 2 because of how late it was manufactured. I believe it was discontinued in 1993 from what I have read. Is there anything else I should watch out for regarding these like common issues or faults? I've also heard people recommend discharging the CRT and other people say it's not necessary. Who should I trust? Thanks!

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It's got some work to do. I already know that. I sure hope the battery didn't explode. I won't know until I get it, though. It says it was manufactured in November 1992, and I read somewhere there were two revisions of the Macintosh Classic II regarding the logic board. I'm thinking this is a Revision 2 because of how late it was manufactured. I believe it was discontinued in 1993 from what I have read. Is there anything else I should watch out for regarding these like common issues or faults? I've also heard people recommend discharging the CRT and other people say it's not necessary. Who should I trust? Thanks!

Discharging the CRT with a flathead screwdriver and alligator clip is not very difficult, but the newer compacts (I know the SE and SE/30 have it, at least) are said to have a bleed resistor for extra safety. I usually discharge it to the ground lug, if I plan to work on the CRT or analog board.

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No video can be a sign of bad caps. I have a Performa 200 (which is a rebadged Classic II) that would mostly show no video, and only on one occasion would show garbage on the screen. Washing its motherboard has fixed the issues temporarily until I can get the equipment and caps for it to permanently fix it.

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make sure the CRT connector is connected.  I have bought a few Macintosh's on Ebay, and every one of them the CRT was disconnected or the 'Brightness' was turned all the way down.

 

You man need the Torx tool to open it

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I've heard cleaning the logic board can help, although temporarily. I know it's not a long term solution, and I'm aware the caps will need replacing anyway, but I would imagine cleaning it can help determine if it's working or there's a bigger problem at hand. I won't know until tomorrow when I get it. I'll check the CRT connections once I receive it. And of course the brightness control.

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Originally, I thought my Macintosh Classic II was getting it delivered on Monday, March 20. However, FedEx said it was scheduled to be delivered on Tuesday, but it never went out for delivery. Later in the afternoon yesterday I checked to see where it was at. It had been stuck in Tracy, CA for over two days for no apparent reason. The past five tracking entries all said Tracy, CA which I thought was odd. I check this morning (Wednesday, March 22) and it finally reached the local FedEx facility. I log in to my gmail and I saw there were a couple of emails, since I opted to get notifications for it. When I read the first email, it said it would be delivered tomorrow (Thursday, March 23) instead of today. Then the email above that said it would be delivered today (Wednesday, March 22). Make up your mind, FedEx!  :lol:  I have never seen so many dates on which it was supposed to be delivered  :lol:

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Okay, so I got the Macintosh Classic II. When I turn it on, the following symptoms are the following:

 

The fan and the hard drive spin up, but there is no chime at all.

Nothing comes up on the screen.

I tried re-seating the RAM modules and did the basic troubleshooting. Still no chime or screen.

Taking it apart, it appeared to be in very good condition internally. I checked all of the connections. Everything appears OK. I replaced the clock battery, luckily no leakage or corrosion from that.

I turned it on while I had the case off, and the tube has a very faint orange glow and everything appears to be getting power. I tried inserting a disk into the floppy drive and it doesn't do anything.

I'm thinking it's the capacitors at this point. Nothing has leaked on the logic board, and I looked for leakage at the base of the caps and there's nothing that has leaked. I assume the caps are failing anyway regardless of whether or not they have leaked.

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It's probably caps, but before doing anything with the logic board, check the voltages (+5V especially, and also +12V). The fan is powered from +12V, but +5V could be missing and you'd see the same result. You can find them on the floppy port on the back -- there's a thread here about it somewhere.

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from ccadams' Mac repair notes

You can measure the power supply voltages without opening up the Mac by prob- ing the appropriate pins of the 19-pin external floppy connector. You’ll find +5v on pin 6, +12V on pins 7 and 8, and –12V on pin 5. Clip onto the threaded standoffs that straddle the connector for a good ground. If your voltmeter’s probes are too fat to make good con- tact, a paper clip will usually do the trick.

 

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Adjust the +5V line to 5.00V, then verify that the +12V line hasn’t been forced too far from +12 (it should be below 12.75V, and above 11.9V). It’s probably not a bad idea to make these measurements both cold and hot, to make sure that there’s no thermal drift to speak of.

 

 

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I checked the voltages from the floppy port and they are in the correct range. The +5v read around 5.0 volts and the +12 reads around 12 volts or something like that. I have it apart at the moment, and I'm thinking at this point it's something to do with the analog board. I noticed the capacitors are of nichicon brand on the analog board. Does this mean they were replaced at some point? And is the flyback transformer known to go on these models? I don't know what else it could be at this point. Thanks!

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I can just hear techknight right now: "For the love of God, recap the logic board!" So, to reiterate: start with recapping the logic board. If that doesn't resolve the issue, then begin troubleshooting elsewhere.

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So I haven't recapped the logic board yet, but I am going to recap both the analog board and the logic board quite soon. Because the CRT isn't turning on, I'm thinking it has something to do with the analog board. The hard drive does spin up, but I don't know if there is anything on it. So clearly it's powering up and it's receiving power, but there is no startup chime and no video. I also grabbed a voltmeter and measured the power through the floppy port yesterday. It is within its normal range for both the +12v and the +5v. The +12v read around 12.36v or something like that, and the +5v read at 5.00v I'm thinking the logic board is okay, but I will recap anyway. Hopefully, I can get this up and running soon.

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You won't see anything from the CRT without a video signal from the logic board. For that matter, the high voltage circuitry won't even power up without a horizontal sync signal from the logic board. So if +5V and +12V are fine, and there's no chime and no video, I'd say caps are by far the most likely culprit, doubly so because it is such a common fault with the Classic II.

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Earlier in the thread, you said the tube had a faint orange glow. What makes you certain the CRT isn't powering on? On a very basic level, if the Mac doesn't boot, nothing will be drawn on the screen. One thing at a time here... Recap the logic board first. If the problem persists, only then should you focus on the analog board. The voltages you show tell me that the analog board is ok. I don't want to sound like a jerk, but I feel like a broken record. Again, recap the logic board, then worry about the other stuff only if the new caps do not resolve the current problem.

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Okay, well I happen to know someone who has experience recapping a logic board, so I'll have him do that first. If that doesn't fix the problem, then we'll troubleshoot some more. He also has experience with CRTs of all sorts and knows the components well.

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