SE SuperDrive - Vertical Stripes after recap

[displaced]

Hi!

I picked up my first compact Mac - an SE SuperDrive with 1MB RAM.
It booted fine, but the display brightness was unstable (dimmed in unison with hard drive access) and the horizontal screen size would jump by 5mm or so every now and then.

So I ordered cap kits from Console5 for the PSU and Analog board. I finished the recap of both earlier - everything went smoothly and I triple checked all values/polarities, etc.

At the same time, I swapped the 4x256K SIMMS with 4x1MB modules, and adjusted the jumper.

Now, when powering on I immediately see a pattern of thick stripes. The floppy drive does do a few accesses, but no chime or boot.

I swapped back to the original SIMMs and jumper config, but the problem persists (although symptoms are different)

I’ve attached two photos: the one with vertical stripes is with the original RAM and jumper setting. The one with horizontal stripes is with the 4x1MB SIMMs and the adjusted jumper.

I’ve also reseated all socketed chips and cleaned the SIMM slots with isopropyl and a soft brush to try to fix this. No obvious physical problems with either my soldering or the logic board sockets that I can see.

Any advice on what to check would be greatly appreciated

 

[displaced]

Bit more info: after leaving it for a few hours, it started fine! Ran well for about 10 minutes, even managed to format a floppy to test my FDD refurb job. Finder showed the full 4,096K…but then it froze. And it’s back to showing the pattern in the photos and won’t boot again.

I’m still sorta suspecting the logic board. Correct me if I’m wrong, but the symptoms don’t seem to indicate that I’d messed something up with my analog board recap. Could it be low voltages from the PSU? I’ll check the readings whilst the system’s running - maybe I need to tweak the pot in the power supply.

Again, though - any ideas welcome!

 

[PotatoFi]

Checking voltages would not be a bad idea! One thing to know: The Mac SE is NOT known to have bad capacitors on the logic board yet. I would not investigate that first, unless you've exhausted other options.

 

[displaced]

Thanks, PotatoFi!

Just curious, do you know some good points to test the +5, +12 and -12V voltages at on a running system?

 

[Byrd]

The external floppy drive connector on the motherboard is a good place to check for voltages

 

[displaced]

Ah yes! Will grab a pin out and give it a test. Thanks!

 

[cheesestraws]

Yup, the external drive connector is the best. The pinout is here: https://old.pinouts.ru/HD/MacExtDrive_pinout.shtml

edit: I know some people here like to recap whole machines at once, but personally I find it more reassuring (if I'm starting with a booting machine) to do one thing at a time: so first recap the PSU, check it still works: then the AB, check it all still works, etc, etc. This way you don't get into the 'I've done multiple things, what on earth broke it' state.

 

[LaPorta]

Another thing to check: look at the solder joints for all of the analog board connectors. They usually have become cracked/flaky. Redoing all of them is usually a good idea. Sometimes that sort of thing can also be caused by that. Ideed, the analog board and power supply will need to be recapped as well.

 

[displaced]

Ok, I’m getting really weird readings from the floppy connector with the machine in its not-booting state.

Struggling to get anything from the 5, 12 or -12 lines. When I do get something stable, it’s 2 or 3V on any of those three. That’s against the GND lines on the socket as well as with touching the chassis itself.

However, I’ve tested +5 and +12 on the hard drive molex and I’ve got 5.28V and 12.2V.

I shall have a check of the joints on all board connectors as suggested - the analogue board in particular has been handled a lot between cleaning, recapping and swapping the fan

And that’s an excellent point about changing one thing at once! Must admit I’m kicking myself just a little bit, since that’s exactly the advice I’d normally give out. Ah well!

At least it’s not utterly dead - couldn’t have messed up the recap and refurb *too* badly! And the floppy drive is smooth as silk after I refurbed it, so there’s that… ha!

Thanks all for the help!

 

[displaced]

So, I've reflowed all the solder joints on the connectors and looked over both the analogue and logic boards closely, but no dice.

I'm not sure if this helps with diagnosis, but I noticed the following:

• The machine will run for a while from cold.
• Formatting a floppy repeatedly will eventually cause strange issues. These include hard lockups, or a wide, white rectangle with a lined border appears about 1/3rd down the screen. It looks like a dialog, but there's no text. The Mac may emit a double-beep at this point.
• Sometimes, the Mac will freeze, but the pointer will still move (unable to click anything). Clicking the mouse causes a beep.
• The only way out is a power-cycle.
• After a power cycle, it will initially boot up fine. But...
• Eventually a power cycle will lead to the corrupted display. However, initially the display will be a chequerboard mix of the lined display and the desktop as shown when the machine was turned off.
• In this state, I need to power off for 10 sec or so. Then, when powering on, I get the lines as shown in the photos.

I think my next step is to fully disassemble again and re-check my work/reflow all touched solder-points. With a bit of luck, my updated observations might spark someone's memory!