1987 Macintosh Plus (Platinum)

[Kai Robinson]

Well, this just fell into my lap! Literally never really thought about getting a Plus before as it seemed kinda pointless with me having an SE...well, a few/eight SE's and SE/30's in various states of being broken...

However, I told myself that if i ever found one for a non-silly price, with the extended keyboard and the mouse, in the platinum case, i'd get one. Pipedream, right? Well, saturn *did* align with mars in this instance and a nice man called Tim came and offered me this for £75!

Of course i practically tore his arm off for it at that price. The caveat? It goes booooop on startup, but high pitched whine and no CRT - so looks like the analogue board needs work, but still - count me in!

A DB-25 BlueSCSI and i'm set! Don't want to mod it, hack it about - just going to clean this one, as it's not all that yellowed. I'll just fix it and use it, although I'll max out the RAM and stick System 6.0.8 on it

 

[Volvo242GT]

That right there was my original Mac. A Plus 1/0 with the platinum case. Came with an A9M0106 floppy drive and an ImageWriter II printer, plus the cases for the computer system and the printer. If you can find a non-ADB Kensington Turbo Mouse 3.0, grab it... A nice little upgrade for the Plus (or any Mac, if an ADB version is found), in addition to more RAM.

-J

 

[max1zzz]

Very nice!

The no video issue is likely just bad solder joints, usually on the analog to logicboard connector, yolk connector or flyback (or all of the above!)
I wouldn't even bother inspecting the joints at this point, just suck all the solder off them and put fresh on. Only start more in depth troubleshooting if this fails

 

[Kai Robinson]

Well, it chimes....then does nothing then chimes...and then chimes...and chimes again

I've just ordered a recap kit and a few BU406's to re-do the analogue board. I'll reflow all the solder joints while i'm at it.

 

[Volvo242GT]

Make sure nothing is intermittently grounding out against the chassis. That exact situation was occuring with my last Plus when I was testing it with a known good floppy drive. If I dare let the drive touch the frame above the board, it would cause the computer to shut down then reboot.

 

[Stephen]

Well, it chimes....then does nothing then chimes...and then chimes...and chimes again

I've just ordered a recap kit and a few BU406's to re-do the analogue board. I'll reflow all the solder joints while i'm at it.

I've seen this boot loop on two separate machines when the 12v line was too low. A wash and a recap (analog board) brought them back to life!

 

[Patrick]

Make sure nothing is intermittently grounding out against the chassis. That exact situation was occuring with my last Plus when I was testing it with a known good floppy drive. If I dare let the drive touch the frame above the board, it would cause the computer to shut down then reboot.

in my experience this also killed the drive.

 

[pfuentes69]

Mine had the reboot issue due to low voltage and the culprit was the optocoupler.

 

[Volvo242GT]

in my experience this also killed the drive.

Mine survived. Is currently installed in my SE FDHD. Works fine.

 

[Patrick]

Mine survived. Is currently installed in my SE FDHD. Works fine.

lucky.

i think a circuit board on the drive touched teh frame of the computer. so ... yeah.. ...
i'm not proud of it. the computer rebooted and the drive stoped showing signs of life.

i wish i kept the drive in the cage or something instead of just holding it in my hand..
<insert defeated male lion leaves meme>

 

[Volvo242GT]

lucky.

i think a circuit board on the drive touched teh frame of the computer. so ... yeah.. ...
i'm not proud of it. the computer rebooted and the drive stoped showing signs of life.

i wish i kept the drive in the cage or something instead of just holding it in my hand..
<insert defeated male lion leaves meme>

Board did touch, hence the reason the computer randomly rebooted. In any case, once the failed component (or components) is found and replaced, it might come back to life.

 

[Kai Robinson]

Been a while since i updated this. So i ordered a recap kit based on the mouser basket in @JDW 's video, here (very useful video btw!):

Unfortunately, I hadn't watched closely enough as this...is for the 120v Analog board. The one in mine is the International one.

Still, most of the caps that came, fitted OK, but i was short two of the big ones, as the International board has four of them.

There is an excellent recap list that @AndyDiags posted back in Feb though, that has all the caps you need, listed here:

https://tinkerdifferent.com/threads/macintosh-128k-512k-plus-240v-analog-board-recap-list.823/

Now although the board was recapped, i had paid NO attention to the flyback. Which was, to put it mildly - buggered seven ways to sunday. @techknight noticed this in one of the images i posted in the Discord server.

Aaaah crap.

Well, $149 and a month later, I have a new-old-stock (26th week of 1991) flyback, courtesy of Dalbani.

I cleaned the board again, recapped with the additional ones that I hadn't ordered last time around and excitedly fitted the analog board into the case, took the Mac Plus into the kitchen (my only real workspace for things like this), and turned on.

"A beep! Yay! It's not dead!"

...it was at this moment, he knew he'd effed up

Then C3 decided 'gotta go kiddo, my people need me' and released it's soul into the kitchen. Awful smell. Turned off the power. Damn.

Maybe it was a bad cap? Ok - let's try it again...

So...uhh...any idea's where i go from here?

 

[AndyDiags]

Can’t tell from the video, but can you confirm W12 is in place so that this is configured for 110v?

 

[Kai Robinson]

Can’t tell from the video, but can you confirm W12 is in place so that this is configured for 110v?

It's missing - as i'm in the UK and therefore use the 240v

 

[JDW]

So...uhh...any idea's where i go from here?

Where did you source that flyback? Is it really compatible? Did the Wurth cap at C3 pop when you had the stock flyback installed?

I ask because C3 connects between +12V and the T1 flyback as follows...

Reasons for C3 to pop would be if polarity was reversed across it, or if the voltage was much higher than the 35V the cap is rated for (possibly on the T1 side) for some unknown reason. Measuring the voltage on either side of the popped cap, with respect to Ground, will reveal the origins of the smoking cap.

 

[Kai Robinson]

The previous flyback was totally destroyed, as was C3 next to it, which is why i bought the new flyback direct from Dalbani (who are the ones that sell them on eBay).

I checked CR1 and CR5 and they seem to measure fine, according to @techknight - but i'm sourcing some replacements anyway.

I replaced the original, blown BU406 as well, with a replacement direct from Mouser, too.

 

[JDW]

The previous flyback was totally destroyed, as was C3 next to it, which is why i bought the new flyback direct from Dalbani (who are the ones that sell them on eBay).

I found this one and this one on EBAY. The second one looks too short, but interestingly, it's the only one that cites Apple compatibility.

If you were to stick that flyback in another known-working analog board and if the same cap blows on that too, then it's definitely the flyback.

 

[Kai Robinson]

That $99 one is the one i bought, as it's the replacement that is put in, in place of the earlier type 26C model.

 

[pocketscience]

So that $99 flyback worked in your Plus?

 

[RetroTheory]

Just to confirm you have the correct flyback by resistance between pins. in Ohms
Low side:
Total ohms: pins 2 to 4: 0.30 = 4,3 + 3,1 +1,2

High side:
Total ohms: pins 5 to 7: 3.50 = 5,8 + 8,7

Pin 6 is not connected.

I found the older flyback has lower resistance, but the rule still stands. You can verify in circuit.