flyback transformer for Mac Plus 1MB

[scroll1]

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.

 

[MacTech68]

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.

157-026C Flyback 157026C / Replaces Apple / HR 42031 | eBay

All credit cards are processed with Authorize.net. © 1982-2015 Dalbani. Serving the Electronic Industry Since 1982. Miami, FL 33166. 4225 NW 72nd Ave. Dalbani is a national and international distributor of high quality electronic components and parts.

www.ebay.com

Line Output Transformer / Flyback: HR42031 (HR 42031) - 1570026B APPLE 157026C MONITRON...

hr 42031, 1570026b apple 157026c monitron 157126v macintosh

www.donberg.ie

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]

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.

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.

 

[MacTech68]

As for heat ... I live in Australia luckily for the Mac Plus we are coming into winter.
cheers, and thanks.

Me too - Perth. And you?

BTW, these 4 electrolytics on that second board appear quite destroyed.

 

[scroll1]

Me too - Perth. And you?

Small World! although, we are on opposite coasts
I live in Brisbane.

 

[JonDS]

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!

 

[Macintosh68000]

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.

 

[MacTech68]

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.

No problem there, they are the same.

 

[Macintosh68000]

No problem there, they are the same.

Thanks for you're help

 

[adderthorn]

Hi everyone. I have been having problems with my Mac Plus as well. I first went the easy route and tried replacing the caps with no luck. With the back off and turning power on I belive the flyback is my problem. I heard a hissing noise that I am familiar with with my other electronics work and saw corona discharge and smelt ozone near the flyback when power was on. You can see the purple electric arcing in the picture from the resin likely decomposing.

I decided to buy the transformer that @MacTech68 listed from ebay. When it arrives I'll install it and let you know if it works. Expensive, yes, but I've bought into my own sunk cost fallacy at this point and with brand new caps, want to give this thing a shot.