Plus trouble!

[LC_575]

I go to turn on my Plus today, and I get to hear this:

chirp, chirp, chirp, chirp, chirp, chirp, chirp, chirp, chirp, chirp, ...

No display, no bong, and sometimes the FDD starts checking the drive ad infinutum.

Turn it off, bring it to my workshop, open 'er up, check the cables, everything seems fine, plug 'er in, turn 'er on, and she boots to the Inquisitive Floppy Disk. OK, all is normal.

Back upstairs, plug everything (SCSI HD, Mouse, and Keyb) back in, and the problem returns.

Now I start different combo's of hardware:

Base Plus Only: Boots to ROM

+ and Keyb: Boots to ROM

+ and Mouse: Chirping

+ and Keyb, Mouse: Chirping

+ and SCSI (OFF) : Chirping or Boot to ROM

+ and SCSI (ON) : Chriping, Resetting constantly at 1Hz, or Boot to ROM with no disk detected (HDD activity light is ON, solid, not blinking)

+ and Everything : You get the idea...

I have not had the Plus running for a few days (was away at College Orientation) but prior it was working just fine.

When I DO get the plus to boot to ROM, the sides of the screen seem to waver slowly.

Based on all of this, I beginning to think either some cap failed or a voltage adjustment is needed. What do you guys think?

 

[mcdermd]

Try adjusting the voltage first. It's the easiest thing to do. When it's off it can make a flub-flub-flub noise.

 

[tomlee59]

You may want to check out some of the troubleshooting hints in the doc found at http://68kmla.org/files. Before twiddling voltages, it's critically important to clean contacts and touch up some solder joints (see doc for details). If you don't do that first, you may permanently damage your Plus.

Good luck!

 

[LC_575]

I'm happy to report some good news:



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Just needed to reflow the solder on all power/sweep connectors.

 

[LC_575]

The problem! It's come back!

Has anyone experienced this "infinite reset" problem before?

 

[LC_575]

After a few searches, I figured out that the FDD may be the problem.

Unplug it, plug back in everything else, flip the switch...

BEWM! Welcome to Macintosh

So how do I fix my FDD's troubles? On boot the inner head would repeatedly engage and disengage (clicking noise). Or is this perhaps the start of a faulty power supply? (Mac resets because it can't put out enough current to power everything?)

Also, it seems that my wavy screen edges have returned. Outside of that everything is fine.

 

[LC_575]

I have figured out the root cause of all my Plus problems as of late:

The voltage regulator pot was WAYYYYY off!

Testing revealed that the +12v rail was only putting out 10.5v!!!. No wonder I had a wavy picture - it's a miracle the Plus ran at all!

Anyways, thanks to all those who helped out. That Plus guide was very useful!

 

[macman142]

Glad you got your Plus working again. The "Classic Mac Repair Notes" are really helpful aren't they!

My Mac ED does the same whup-whup-whup infinite reset which is referred to as "activated crowbar."

Unfortunately re-soldering many joints and adjusting R56 did nothing for me and mine will need a replacement analogue board

Testing my logic board in a spare 512k Mac brings up a "Sad Mac" too so looks like it's suffered a fairly serious failure all round!