Mac Classic 2 Problem Diagnosis.

[Mars478]

Hey everyone!

I Bought a Macintosh Classic 2 off of Ebay for 10 $ (Plus 22 Shipping ) . It comes with a keyboard and a Mouse. The Description says that it starts up to a Flat line on the CRT and that the Vertical Sweep circuit is blown out. According to this site: http://www.biwa.ne.jp/~shamada/fullmac/repairEng.html

They Say

"(1) The first thing to do is to check the P1 connector. If the problem is caused by connection/soldering failure of the P1 connector, you will see the burnt and/or charred P1 connector. Desolder, clean and resolder the P1 connector.

(2) If the problem still persists and the culprit is the U2 IC chip, replace it with a new TDA1170N chip.

When the U2 IC chip is broken, you may see another symptoms such as:

(1) The screen is shrunken to the upper/lower half of the monitor and the opposite half blacks out,

(2) The upper/lower half of the screen is extended in the vertical direction."

Does anyone know of this Problem on a Classic 2? The site above was made to repair the Macintosh SE and not any other...

Thanks!

 

[tomlee59]

Lack of vertical deflection in a compact Mac is almost always caused by a poor connection. Resoldering (with fresh solder) the yoke connector should be performed as a matter of course. After doing so, pull out the cable and inspect the mating surfaces for oxidation, burning, etc. Repair/replace as necessary.

In very rare instances, the vertical deflection IC blows. IIRC, it is still a TDA1170 in the Classic II. This chip is very common, and probably still widely available. But resolder the yoke connector first, and see where things stand at that point.

 

[Mars478]

Hey there! Thanks!

I Got it and test started it. It makes a strange fart like sound on start up. and there is a flat line on start up.

I haven't taken it apart yet but I will.

 

[Mars478]

Actually the Fart sound stopped...

I get a Bright Horizontal Line but no chime.

 

[Damian Ward]

HI Mars478, I would tackle the vertical scan collapse first. As Tom said re-solder the connector and see it that works. The missing chime is most likely due to leaking capacitor on the logic board, the Classic II's are notorious for that. It's probably best to sort out one thing at a time. Just be careful not to run it too long with the white line showing, it will burn into the phosphorus, leaving you a permeant line.

 

[Mars478]

Thanks! I am a new to the Compact Macs so How would I get to the Analog board without dying

Is there a Guide?

Also the Line on the Screen spans edge to edge. It is different from Damians Picture on Flickr.

 

[Damian Ward]

Have you managed to download Tom's notes? http://68kmla.org/files/classicmac2.pdf The notes go into detail about the hazards of working inside a compact and how to discharge a CRT. The line is probably different because the CRT width is set wider.

 

[Mars478]

Yeah I downloaded the PDF.

I see no visible Corrosion on the Analog board or on the connector that is showed.

To Remove the analog board I have to discharge the CRT?

Thanks!

 

[Mac128]

To Remove the analog board I have to discharge the CRT?

Yeah I would. But you may not have to remove the analogue board to make the repairs.

According to Larry Pina's Mac Classic Repair book, most likely a horizontal white line is a symptom of a broken or cracked solder joint at connector BD1 on pin 1 on the bottom of the connector. The crack may also be on the width coil at LL2 or on the horizontal deflection capacitor at LL1.

In which case, all you need to do is remove the vinyl jacket and re-solder the joints at these locations.

 

[Mars478]

Here's a bad update. I posted this to another forum, and I got the reccomendation to whack the top of the case, it did bring the video back for HALF a second but the video went off. Now I get no video...

Any idea how to fix this!

Hahahahahh!

 

[Mac128]

I got the reccomendation to whack the top of the case, it did bring the video back for HALF a second but the video went off. Any idea how to fix this!

Yeah, follow the advice you have been given here. Whacking the top of the case is not likely to hurt it, beyond what is already damaged, but it is a common remedy that might temporarily resolve this particular problem. What whacking it does is temporarily make contact with a weak or cracked solder joint, until the high frequencies running across it vibrates it apart again or the Mac gets jostled. Most likely in your case whacking the Mac caused a permanent break in the solder, too far apart to to be mitigated by this rough approach. If you allow it to sit power up for several hours, the expansion from the heat might allow a good whack to make a connection. Other other hand, it could further weaken other joints. The only way to fix this is to go in and re-solder the suspect joints.

This more or less confirms what most of us have been thinking.

 

[Mars478]

Yeah I'll keep it running for a while without brightness (so that the phosphor does not get burnt) for a while...

Thanks I'll update this soon.

 

[Mars478]

Hi, I left it running for about an hour and I got no video at all.

Should I just resolder all the connections on the Analog board?

Arghhhhhh I WANT THIS TO WORK!!!

 

[joshc]

Hi, I left it running for about an hour and I got no video at all.Should I just resolder all the connections on the Analog board?

Arghhhhhh I WANT THIS TO WORK!!!

Follow the good advice already given here, which is to resolder all joints that look suspect. Another thing to consider is replacing the capacitors on the analog board with new ones. By doing this, you will avoid the potential problem of leaking/bulging capacitors in the future. When working near the analog board, yoke, anode cap/lead and video board, make sure you have discharged the CRT to the ground lug first. This will ensure you are protected against serious injury. Possibly more importantly, take it very slow when working inside the machine -- knocking the end of the neck is easily done if you're not careful, and will result in a dead CRT.

 

[Mars478]

I know the CRT is working because there is a little light in the Glass neck.

Also is this an example of Corrosion on my motherboard?

 

[Mac128]

resolder all joints that look suspect.

Chances are a cracked solder joint will not be visible to the naked eye. Take note of the locations I mentioned above per Larry Pina's repair instructions and re-solder all leads attached there, whether they appear to need it or not.

And yes your logicboard appears to show a leaky capacitor. It may need to be replaced, but definitely cleaned and probably re-soldered.

 

[Mars478]

There are some solder joints on the analog board that seem to be more brownish in color. Is that A bad solder joint?

 

[Mars478]

So I am going to reflow all of the suspicious Solder joint which look brownish right?

 

[Mac128]

So I am going to reflow all of the suspicious Solder joint which look brownish right?

No you are going to identify the solder joints at the locations I and others specified above. If it is clear that the solder joint was scorched, and not just discolored, then you have a component failure as well. The best way to identify that is to look for scorch marks on the back of the white vinyl panel that covers the analogue board. Otherwise as pointed out earlier, cracks in solder joint are usually not visible without microscopic inspection. If you see any obvious defects, then by all means secure the connections. Otherwise, it is best to proceed location by location. If the places I have relayed from Larry Pina's book to not restore the Classic, I can give you a list of all the trouble spots to investigate. Though from the description of your problem, I gave you only those that applied.