Macintosh Classic Blank Screen

[PotatoBox]

I bought a macintosh classic from a local collector that wasn't working, as my first compact mac project.

Currently, when I try to power it up, the CRT does not come on (analog board issue?), as well as no chime.

Sometimes when I apply power, there will be a white beam that sort of fills the screen 10-15 percent, very briefly, then it'll stay blank.

I checked inside and the logic board seems intact with no battery leaking or anything. I didn't go further due to me still needing to make a CRT discharge tool.

How should I proceed? This sounds like something wrong with the analog board, so I guess I will start there. any kind of helpful advice would be greatly appreciated.

The only thing I fear is that the previous owner went through this process and concluded that it is not repairable.

 

[jasonfortheworld]

Definitely check all the solder joints on the analog board once you are able to discharge the CRT.

Look for anything that may need to be reflowed. Intermittent power could very well be a sign of cracked solder joints that don't make good or consistent contact.

Next step would be to recap the analog board (and probably logic board as a precaution).

Those are the most common failures these have.

 

[PotatoBox]

Definitely check all the solder joints on the analog board once you are able to discharge the CRT.

Look for anything that may need to be reflowed. Intermittent power could very well be a sign of cracked solder joints that don't make good or consistent contact.

Next step would be to recap the analog board (and probably logic board as a precaution).

Those are the most common failures these have.

Is there anything on the analog board that can't be recovered from? like a bad transformer?

 

[jasonfortheworld]

Is there anything on the analog board that can't be recovered from? like a bad transformer?

I'm not to sure. I know that Flybacks are hard to source and expensive, but otherwise I'm not directly familiar with the classic analog board.

I would take a look at the Dead Mac Scrolls book and see what it says about your symptoms.

 

[s_pupp]

Definitely recap, even if it turns out not to be the cause of your problem. Leaking electrolyte is a problem with that model.

Back 12 years ago, I recapped my wife’s Classic’s logic board due to a leaking capacitor, and brought the dead Mac back to life.

Last year, after being in storage 12 years, the Classic wouldn’t boot. When I removed the analog board’s capacitors, most of them were dripping electrolyte. Cleaning the analog board and replacing the capacitors with a kit from Console5 brought the Classic back to life again.

 

[cheesestraws]

Yes, to put it politely, those analogue boards are "cost-optimised". By which I mean they're cheap to the point of self-destructing. Recapping 'em is pretty much vital.

 

[bibilit]

I agree a 100% with all above, by far the Classic is the more unreliable unit ever built, it was a cheap put together item at the time, and still is today.

It was a Macintosh Plus in new clothes, but with prone to failure new capacitors, in the Logic Board and Analog side.

Start with new capacitors all around first and keep an eye at voltages.

 

[LeSpameur]

It's very rare to find a Classic or Classic II working without a recap (analog board + motherboard). I recommend cleaning the analog board with soapy water — isopropyl alcohol isn't sufficient. Do the same for the motherboard. You might also need to repair broken traces on the motherboard.

 

[ESM-NL]

I recommend cleaning the analog board with soapy water — isopropyl alcohol isn't sufficient. Do the same for the motherboard.

I don't think that soapy water is a great idea. I did that ones years age with a logic board from an SE/30 and it never came to life again.

 

[LeSpameur]

I don't think that soapy water is a great idea. I did that ones years age with a logic board from an SE/30 and it never came to life again.

You probably didn’t let it dry properly, and it caused a short that fried something. I clean every board I have with soapy water in my ultrasonic cleaner, and I’ve never broken anything that way.

 

[ESM-NL]

You probably didn’t let it dry properly, and it caused a short that fried something.

Yeah, could be. I don't remember how long I've let it dry. Luckily I was able to find a new-in-the-box-replacement board back then, so the "problem" was solved.