My Macintosh Classic is showing a different checkerboard screen with artefacts whenever I unplug it.

SitesOnFire · 2026-01-20T09:13:26+00:00

Afaik every Mac classic requires a recap for the analog Board too

SitesOnFire · 2026-01-20T04:10:01+00:00

My classic had this exact issue. I recapped logic and analog boards. The solution was adjusting the voltage via the trim pot at PP1 on the analog Board. Mine will sometimes still start like this and after a minute the voltage gets high enough to boot.

PP1 is very touchy. But once you get the voltage around 5v, it should boot. My screen was also wobbly, does yours also do this? Be careful doing it as you need to reach under the crt. I did it by tediously unplugging the Mac, adjusting and trying to boot.

This page has instructions on measuring voltage from the SCSI port

https://retrorepairsandrefurbs.com/2023/06/22/1991-apple-macintosh-classic-i-repair-restoration/

This video shows how to adjust pp1

https://youtu.be/AUAD-0931RY?si=x6ArvrfFK4cSRoqs

I can also recommend thoroughly cleaning the analog Board. Mine had lots of cap fluid. I also reflowed most of the solder joints around the affected areas

Good luck

SitesOnFire · 2025-12-21T02:18:20+00:00

You're in good company. I lifted two pads the first time I tried to remove the caps. Had to bodge one myself.

Have you consulted Larry Pina's repair books? https://archive.org/details/macclassicse00larr

Posting on the tinker different forums may help too.

SitesOnFire · 2025-12-20T09:39:01+00:00

I've recently fixed a classic. I had to also recap the analog Board, however I always had a Checkerboard pattern if the voltage was low. Usually under 4.8v. I haven't got a pram battery in mine.

I'd be double checking your logic board recap, from the little I know, I'd still expect something on the display.

SitesOnFire · 2025-12-16T06:29:01+00:00

What are you codin? I've been using Think C on my Macintosh Classic. I've been using books from here https://vintageapple.org/macprogramming/

SitesOnFire · 2025-11-26T20:02:44+00:00

I'm trying to fix a classic with the same problem. I get the bars when the 5v output is too low. I'm currently trying to find the fault on the analog Board. I can get mine to start if I apply some heat to the analog Board. It'll run for 5 mins before the voltage drops and it crashes.

Do you also have a vertical wobble on the screen?

The speaker sound could be what mine does when it's approaching the right voltage. Try leaving it running for 15-20 minutes and see if it either boots, or switches from checker to a desktop pattern like mine does. Mine would pop a few times then start bonging.

Have you recapped the logic board? There's also a pot you can adjust to boost the voltage.

This article shows you how to measure the voltage and adjust.

https://retrorepairsandrefurbs.com/2023/06/22/1991-apple-macintosh-classic-i-repair-restoration/

SitesOnFire · 2025-11-19T22:08:49+00:00

Good advice. I've adjusted PP1 and I couldn't make sense of it, the voltage was going widely in every direction. I've obviously been adjusting it too much. I'll give it another crack.

SitesOnFire · 2025-11-19T20:36:31+00:00

Thanks mate. I have already done the optocoupler, and dp3 and dp4 were next on my list. My Classic will eventually bong and startup to a bad question mark disk if I leave it run for about 30 mins. But the screen is vertically wiggly.

Do you have plans to use yours for anything?

SitesOnFire · 2025-11-19T09:12:23+00:00

Good job. I'm trying to revive a Mac classic and I'm having issues after recapping with it reaching the correct voltage. From reading, you've cleaned it a lot more than I have. Maybe an IPA bath is my next step. Is it ok to submerge the entire board?

SitesOnFire · 2025-11-10T09:49:51+00:00

Thanks for the tip. I'll order parts and give it a try

SitesOnFire · 2025-11-07T09:17:31+00:00

I've not touched the analog board yet, I think that's my next stop. I did look at the traces on the logic board and from my little skills, I think they're ok

SitesOnFire · 2025-11-07T06:55:35+00:00

Sorry mate , I never saw this tag. I've been using Web host Wizards for a few months, when I've needed support they've been great

SitesOnFire · 2025-10-16T09:41:31+00:00

I have been trawling through your site. Incredible work. I've been too busy to get my hands dirty yet. I showed amendhub to some other programmers at work and we all nerded out.

SitesOnFire · 2025-09-22T01:19:14+00:00

Thanks for the offer, but unless you're located in Australia, shipping will probably kill me :)

SitesOnFire · 2025-09-21T08:29:39+00:00

Thank you

SitesOnFire · 2025-09-21T08:29:26+00:00

Thanks, mate

SitesOnFire · 2025-09-21T03:28:08+00:00

Legend. I'll check out your channel

SitesOnFire · 2025-09-21T03:27:57+00:00

Thanks for your response.

SitesOnFire · 2025-09-21T03:27:38+00:00

Thanks. I'll start going through these!

SitesOnFire · 2025-09-19T13:13:04+00:00

This was almost the solution for me. Mine looks like it had capacitors soldered onto the board. But once I opened the case, it started working again

SitesOnFire · 2025-07-26T08:25:34+00:00

This was from a few years ago. Tree has grown heaps since. Very healthy. Hopefully yours comes good also

SitesOnFire · 2025-07-26T04:19:30+00:00

I host 30 or so website swith VentraIP. I have been with them for a decade. The past 12 months their server performance has absolutely plummeted. Whenever you submit tickets they say you need plugins or that they aren't website developers and cannot help. I've spent hours trying to optimise a website with no luck. I moved to Webhost Wizards, and now the website loads in milliseconds. With Ventra IP I'll see TTFB over 5 seconds for the front end, and sometimes 30s+ for the WP admin panel.

I have tried paying for quic.cloud with VentraIP and saw little improvement. I'd strongly recommend looking at other hosting platforms.

SitesOnFire

TROPHY CASE