scroll1

macrumors newbie
Original poster
Jun 16, 2020
3
1
Hi,
I have a Mac Plus and a Mac Plus 1MB with keyboard and number pad (no mouse). The have been in storage for years and finally I got around to inspecting the Mac Plus 1MB. It looks like I have burn marks around Q2(international version) BU406. After reading "Macintosh Repair and Upgrade Secrets", all things seem to be pointing to the flyback transformer. Visual inspection shows cracks on the top (see pics), but the model number is not mentioned in the book (157-0042-C), is this even a replacement board? I'm just wondering what version of the transformer should I be looking for on the web (if at all I can find one!!) ... anyway, while I what for this one to be sorted, I guess I go back to my 9" Apple IIc monitor repair :) thanks for any pointers or advice in advance.
20200617_130334_HDR.jpg
20200617_130329_HDR.jpg
 

MacTech68

macrumors 68020
Mar 16, 2008
2,347
189
Australia, Perth
Any model you can get your hands on will do the job. Yes, they do fail and I can only suggest NOT using the MacPlus on a very hot day.

It the heatsink the BU406 is mounted to, a blue-ish/purple color - pic would help.

The board is a fairly late revision in the service part's lifetime. Some observations:

1. Litzwire L1 (and assuming L2)

2. larger sized CR1

3. White axial polycarb HF C1

4. FBT date code January 1991

I don't recognize the label on the FBT, but the partnumber (157-0042C) is correct for one originally found in the MacSE or supposedly a repaired board. However, preference seems to be to use the 157-0026C, used in the late Mac Plus.

The only two VERY EXPENSIVE source I've found is DalbaniCorp in the USA and Donberg - below link is NOT an endorsement - Buyer beware.



Otherwise, buying a scrap MacPlus from your local market eBay/craigslist/recycler (etc), may get you the parts you need. Even if it is not working, it may still have a usable FBT & BU406. YMMV
 

scroll1

macrumors newbie
Original poster
Jun 16, 2020
3
1
thank you MacTech68,

I have a broken Mac Plus (that I thought of also restoring, but it may prove more handy as donor). I opened it up for the first time today only to find that it has been missing parts, even Q2 is missing which may indicate the FBT has gone in it as well.
MacPlus.jpg


I guess there is no easy way of testing the Flyback transformer, other than trying it out. I need to wait for a new BU406 though. I will remove the BU406 anyway and test it out of the board, table 5-5 on pg 101 in the "Macintosh Repair and .." book shows what to expect from a good one.
As for heat ... I live in Australia :) luckily for the Mac Plus we are coming into winter.
cheers, and thanks.
 

JonDS

macrumors newbie
Jul 10, 2020
1
1
thank you MacTech68,

I have a broken Mac Plus (that I thought of also restoring, but it may prove more handy as donor). I opened it up for the first time today only to find that it has been missing parts, even Q2 is missing which may indicate the FBT has gone in it as well.
View attachment 924937

I guess there is no easy way of testing the Flyback transformer, other than trying it out. I need to wait for a new BU406 though. I will remove the BU406 anyway and test it out of the board, table 5-5 on pg 101 in the "Macintosh Repair and .." book shows what to expect from a good one.
As for heat ... I live in Australia :) luckily for the Mac Plus we are coming into winter.
cheers, and thanks.
Wow Scroll, I had a similar problem on my MacPlus analog board with the burned out 4 pin yoke connector (J1). Fortunately I was able to replace it (and the yoke) and it's working great now, though I also wonder about my flyback. MacTech is right, that's the only place I was able to find them for sale, but they are a little steep in price. P.S. I'm not Australian, but I've been there on several occasions for work - Brisbane twice - lovely city!
 

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Macintosh68000

macrumors newbie
Jan 19, 2021
15
2
Does anyone know if a flyback from a 120v original Macintosh analogue board model number AC-058ZBBT works on a 240v Plus analogue board as I have a spare one and my flyback on the plus is toast.
 
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