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Starting a Mac Plus restoration. Need a new flyback wire with anode cap

Posted by: reallyrandy on 2021-09-06 16:24:18

This poor thing has been in storage since the early 90s. I was gonna use it as a donor Mac but it turns out I don't need any parts from it. So, I decided to try and resurrect it.

I plugged it in with my Floppy EMU to try a boot and just got clicking from the PSU (not surprised). I started taking it apart and after discharging the PSU noticed that the flyback cable and the cup at one end and the rubber shield at the other end have pretty much turned back in to oil.
Are there any sources for a cable like this? Other than a donor Mac?

Also, that glue on the flyback looks pretty cracked, can I buy a tube of that stuff? It looks like it's some type of putty.

Posted by: reallyrandy on 2021-09-06 18:08:25

Got it taken apart and the whole inside is covered in black soot, WTF?

Posted by: Byrd on 2021-09-06 19:02:54

Black grime is not unusual in an old computer case, but if really sooty I'd say it's been in a fire - as evidenced by the cracked rubber anode cap

Posted by: bdurbrow on 2021-09-06 19:27:38

Or had the fire internally; as a fire outside of the case would have melted the ABS plastic case first, before scorching the electronics inside.

Posted by: Iesca on 2021-09-06 20:04:10

The "glue" around the flyback is an epoxy, and it can be reapplied. As for the grease under the anode cap, it seems you may be able to use silicone grease, or even Vaseline.

I would be very concerned about that flyback though.

Posted by: reallyrandy on 2021-09-07 09:50:04

It looks as though all the soot is originating around the flyback. The soot is mainly on the flyback, the flyback cable and the back of the CRT where the anode cap is. The clear anode cap and the the cap at the other end of the wire leading into the flyback is kind of "wet" with an oily feel, like the transparent rubber is turning back into oil. Does anyone know where I can source a new flyback with the cable?

Is there a good way to clean the back of the CRT? I'm pretty sure I can't just wash it!

Posted by: reallyrandy on 2021-09-07 15:46:24

After some cleanup:

Posted by: Byrd on 2021-09-07 17:18:39

Nicely cleaned up - it looks a lot better. I reckon that flyback has been arcing attracting the dust, can you see any deep cracks or scorch marks around it? I'd be wary trying it once recapped, don't get close, and prepare for your house circuit breaker to be tripped 🙂

This is an example of an overpriced flyback for the Plus:

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

Posted by: Iesca on 2021-09-07 17:31:26

You may be better off just getting a replacement analogue board, sadly.

Posted by: davidg5678 on 2021-09-07 17:58:35

I think that you did a good job cleaning up this anode cap. All of my Macs have had degraded rubber anode caps and sooty CRTs like this. I always just cleaned up the mess with an isopropyl alcohol-soaked paper towel. After I remove the degraded rubber, the remaining (non-oily) material had always seemed more than solid enough, so I haven't been too worried by it.

There is supposed to be a dielectric grease applied in the factory between the CRT and anode cap. This grease should be left behind if you can manage it, though several of my computers are missing the grease and still work fine. I think it's supposed to prevent arcing in the event the anode cap doesn't make a good seal.

I always assumed the soot was just some kind of dust attracted by the high voltage components in the computer. From what I've seen in these pictures, I really don't think this computer was ever internally on fire, so again, no worries.

Personally, I would try powering up this computer. It looks like it has a good chance of functioning now that you've cleaned it, and the degradation I can see looks pretty standard.

The flyback may be a bit worn, but I have seen worse. The glue looks a very dark, but I can't make out any cracks, so I think it's probably fine for now. The main concern would be if there is a lot of glue missing around the flyback and that it starts arcing (and making ozone?).

The PSU in this computer may be bad, so made sure to verify its function before connecting it to the rest of the machine. Especially if this is an Apple Singapore model PSU, it may just be completely destroyed by capacitor leakage.

Remember to take safety precautions if you're unsure of anything's reliability!

Posted by: reallyrandy on 2021-09-07 19:03:08

I'm seeing an analog board on eBay that looks clean, I may just go for that. If nothing else, I'll have a spare.

Posted by: reallyrandy on 2021-09-12 13:36:09

Retrobrite day! I figured I'd do some extra things since I already had the tubs filled.

Posted by: reallyrandy on 2021-09-14 14:08:52

All refurbed and ready to use!

Posted by: reallyrandy on 2021-09-15 09:44:21

I fired up the Plus after reflowing the solder joints on the analog board. I get a beep and my Floppy EMU lights up steady now. Unfortunately, the screen stays black. I'm guessing this points to the flyback. Are there some tests I can run to see if that is in fact, the issue?

I see only one analog board on eBay that looks promising. Still, that one has not been tested.

Posted by: Virtual Davey on 2021-09-15 10:00:15

I fired up the Plus after reflowing the solder joints on the analog board. I get a beep and my Floppy EMU lights up steady now. Unfortunately, the screen stays black. I'm guessing this points to the flyback. Are there some tests I can run to see if that is in fact, the issue?

I see only one analog board on eBay that looks promising. Still, that one has not been tested.

I had seen in a video that if the "glue" on the flyback is brown (not yellow like it should be), there could be an issue. Also if you look at the flyback in complete darkness (while the unit is on) and you see "blue sparks" flowing inside of the flyback, that could also point to a defective flyback. At 15:41 in this video:

Posted by: cheesestraws on 2021-09-15 10:04:22

Unfortunately, the screen stays black. I'm guessing this points to the flyback. Are there some tests I can run to see if that is in fact, the issue?

There are a number of parts on the AB that can fail in the video path that aren't the flyback. Do you have an oscilloscope or any other means to trace signals? This for me was caused by a bad inverter chip (which forms the first part of the video amplifier).

Posted by: reallyrandy on 2021-09-17 19:41:07

I don't have anything but a multi-meter. I may just look for an analog board and donate this one to someone who can fix it.

Posted by: reallyrandy on 2021-09-23 13:30:30

I was offered an analog board by CC_333 so I'm gonna go that route and save this one to fix later. In the meantime I got my 128k and my 512k running beautifully. I had to take apart, scrub and re-grease the 400k floppies in both.

Posted by: Iesca on 2021-09-23 15:35:34

I was offered an analog board by CC_333 so I'm gonna go that route and save this one to fix later. In the meantime I got my 128k and my 512k running beautifully. I had to take apart, scrub and re-grease the 400k floppies in both.
View attachment 34333

Wow, that floppy drive is in beautiful condition!

Posted by: reallyrandy on 2021-09-23 20:16:57

You shoulda seen it when I took it out. Everything was seized up, no eject, couldn't even slide a disk in. I soaked it in alcohol and then scrubbed it in Windex. I used white lithium grease on the metal parts and silicon lube on everything that touches plastic. Now it's super quiet and moves easily. The caps all look good so no re-cap… yet!

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