Mac Plus beeps, then nothing… occasional reboot beeps at random intervals

[reallyrandy]

I have my original Mac Plus that I bought in 1986. It's been in storage for about a year. I just took it out and tried to boot it and got a beep and then nothing. I have a 6.0.8 boot floppy in the drive but then I hooked up my Floppy Emu and it lights up but keeps going in to self test mode every 20 or 30 seconds. If I leave the computer on for a few minutes, it starts beeping again like it's restarting at random intervals about once or twice a minute. Other than that, there is no sound at all (I didn't realize the Plus has no fan). On some boots I get a pattern on the screen and sometimes it's just dots here and there. The MB looks fine and the analog board looks fine too. No bulging caps or gunk on the board.
I mentioned it to Thomas from @Amiga of Rochester and he said Pluses don't really need recapping, so I'm suspecting the analog board. I'm a developer but know very little about electrical. I have a meter but only know how to use it for testing a wall plug or wire continuity.
I've attached some pics, maybe one of you can spot something?

 

[cheesestraws]

That all sounds very much like the power supply is struggling. The PSUs in these are known to cook themselves, because they aren't very good. Recapping the PSU portion of the AB may help, but power supplies aren't my strong point.

 

[dochilli]

Check the voltages at the floppy port. Must be 5 and 12 V.
See figure 4 at:

Apple Macintosh Plus checkerboard screen repair

I would recap the analog board.

 

[desertrout]

I've seen something like this because of a dodgy connection between the logic board and analog board... so along with verifying voltages as @dochilli suggests, I'd look closely at the J4 header on the analog board for cracked solder joints. In fact, it's good policy (imo) to just resolder any headers as they are notorious for causing problems.

A general recapping is also a good idea, and @JDW 's video is an excellent resource:

 

[reallyrandy]

I get around 10v from pin 7 and 4v from pin 6. I left it for a few minutes and it actually booted from a floppy!

I still need to get it fixed though because it's not reliable.

Does it sound like a cap issue or maybe the flyback is bad? It looks a little corroded.

If there's any Mac I want in pristine condition, it's this one. I've had it 35 years.


I

 

[joshc]

Those voltages are very low. That's not a flyback issue, the picture is fine. The flyback just looks like that because of age (also possibly because of how it has been stored?). The darker colour of the sealant/glue around the top indicates it was run for many hours back when it was in regular usage.

Replace all the electrolytic capacitors and go from there. These analog boards suffer from weak/dry solder joints because of the Plus's lack of fans, so every solder joint on the analog board should be reflowed with new solder as well.

Good luck with it.

 

[cheesestraws]

Agree with @joshc, definitely not a flyback issue. The flyback controls the CRT, and that looks OK.

If it came on on its own after a little while, that almost sounds thermal; perhaps that points more towards dodgy solder joints than capacitors? Either way, both are known to be questionable on these machines, so really, you should expect to have to replace caps and fix up solder joints.

Sigh.

 

[reallyrandy]

Josh and Cheese, that sounds like sage advice. Now I gotta find someone who can reflow solder joints. I've never done it and don't have the equipment. I would love to learn on an old radio or something but I don't want to experiment on a Mac that's this important to me.

To further validate your suspicions, This Mac exhibited the same behavior (beep, then nothing) for a few days and several tries until I took it apart and messed with it. I guess moving and flexing the analog board jiggled the connections and allowed it to boot.

This Mac got really heavy use back in the 80s. I laid out most of the Long Island Yellow Pages books on this Mac using dBase Mac, PageMaker, and Cricket Draw. I used it heavily between 1986 and 1991 for my graphic arts business. Is there a way I can re-glue the flyback to make it new again? I don't even know what kind of glue it is. Or maybe someone here can do a complete refurb of the board?

It's always been stored in a climate controlled environment with the battery removed (as are all my Macs). I have some of them on display now so no more storage.

 

[dochilli]

Reflowing the solder is easy. You can try to reflow the old solder. Better would be to use new solder. You will need a solder iron, because I think your second compact mac (SE or Se/30?) needs a lot of recapping as soon as possible. The same for the color classic!
I learned the soldering and recapping with my compact macs.

 

[desertrout]

If it came on on its own after a little while, that almost sounds thermal; perhaps that points more towards dodgy solder joints

Yep, definitely. That and the (very) low voltages, it's pretty obvious that the typical recap/reflow procedure is required. Surely there is someone on the forum in your area that may be able to assist? You could also ship it to someone - might be worth sending up a flare in the Trading Post forum.

 

[reallyrandy]

@dochilli , The color Classic is already recapped but the SE will be needing it too.

 

[reallyrandy]

I found a few cracks in the solder where the cable attaches to the side of the CRT. And there are brown stains at C1. But C1 is one of the black and white caps that don't leak. Maybe it's just flux?

 

[desertrout]

Those C1 joints don't look suspect to me (that residue does look like old flux), but it should be included in the recap with an uprated film cap anyway.

 

[reallyrandy]

I re-soldered all the bad joints on the PSU and it fired right up! Nice and bright!
I bought a X-Tronic soldering station and some no-clean flux and some wick. That flux is super sticky. Alcohol doesn't do a great job cleaning it off the board, is there something that works better?

All the caps on this PSU look great. No leaks underneath and the tops are flat. It's been stored in a 75° room in a cardboard box. I think that made all the difference.

 

[desertrout]

That's great! Nice work.

Isopropyl alcohol (90% +) should work just fine on no-clean flux, though I find it needs to be 'scrubbed' off with a q-tip or a brush (I use a toothbrush). Then mopping up with a lint-free paper tissue like Kimwipes or something similarly absorbent. There's also specially formulated flux remover (https://www.mgchemicals.com/products/soldering-supplies/flux-removers/flux-remover-for-pc-boards/), which some prefer but I've never used it.

 

[cheesestraws]

Your "no-clean" flux doesn't sound very no-clean . Perhaps through a technicality...

Nice work on the resoldering. The Plus is a really good machine to learn this kind of stuff on, because everything on it is reasonably chunky and easy to actually reach, and none of the bits of it are particularly rare (with the possible exception of the flyback and one of the SCRs), so if one mucks something up it's usually either fixable or a spare is available.