Macintosh SE with horizontal lines, no chime

[mattsoft]

I have an SE that when powered on does not make a chime and displays these lovely horizontal lines. Initial inspection of the motherboard looks good. Anyone familiar with these symptoms? Gonna check voltages next. Thanks!

[Nathanplus]

Always start by re inserting the ram after cleaning each one with isopropyl alcohol. If that doesn't work try configuring the SE with 512k and check each ram stick by swaping them untill you get the machine working.  

[mattsoft]

I cleaned the SIMMs and sockets. This SE has 4MB of RAM (4 X 1MB SIMMs). With the 4 SIMMs installed, I get the horizontal lines.

 

I removed the 2 SIMMs from slots 3 and 4 so it only has 2MB of RAM and I get a black screen. Swapping the 4 SIMMs around so that only the 1st 2 slots are filled always gives a black screen.

 

If I put 2 SIMMs into slots 1 and 3, I get vertical lines. This config shouldn't work, so I guess that makes sense.

 

Maybe I have 3 or more bad SIMMs. What I need is a working SE to start swapping parts. Will keep a lookout for one in the area.

 

Thanks!

 

 

 

[dochilli]

IF the SE does not chime, the ROM can be the problem. Remove, clean and reseat the ROM.

[CharlieFrown]

examine the pins underneath the mobo - might be bent in the way they cause short circuit. Sounds strange, but I had the recapped SE/30 with the same issue. 

Edited May 13 by CharlieFrown

[mattsoft]

Well, I figured out why I was getting a black screen when only 2 SIMMs were installed. My SE logic board has the 150 ohm resistors at R35 and R36. On my board, R35 was cut and R36 was removed. I soldered 150 ohm resistor on R36 and put 2 SIMMs into slots 1 and 2 and instead of a black screen, I get the same damn horizontal lines. I swapped all 4 sticks of RAM around in those 2 slots and always got the horizontal lines. So either I have 4 bad SIMMs or it's something else.

 

I removed all 3 ROM chips, cleaned the pins and sockets and re-inserted. No change.

 

I also tested the voltages on the power molex into the motherboard. Everything looks good.

 

Checked all the pins on the bottom of the logic board and nothing appears to be bent or shorting anything.

 

At this point, I'm stumped. If someone has a working SE motherboard they'd like to sell cheap, I'm all ears!

 

Thanks!

Edited May 14 by mattsoft

[dochilli]

Did you check the voltages at the external floppy port (+5, +12, -12 V)?

 

Edited May 14 by dochilli

[mattsoft]

So I found a working SE and swapped main boards. The broken SE (now affectionately known as old stripey) works fine with the working main board. So the horizontal stripes is something on old stripey's main board. I swapped the ROMs and still no luck. So it must be some other component on the main board that has given up the ghost.