Glowing Flyback Transformer

[tt]

I noticed the flyback transformer on the analog transformer of my SE/30 has a crack that is glowing (top of the cylinder). Does this mean it is going to fail? Should I stop using it? Anyone have a spare?

 

[JDW]

If you have seen some on-screen glitches or noise, I would think the flyback would be about to fail. But if you are not seeing anything unusual, I wouldn't worry too much about it.

I have a very different problem on my SE/30's flyback, and it works just fine even with this metal part broken in two:

https://picasaweb.google.com/103365672326265854011/SE30MicronXceedGrayscaleVideoWithDaystarSnapOnAccelerator#5641720139650991042

 

[tt]

There are some on-screen slight waves/ripples that happen usually soon after booting. I was thinking it is because of the power supply. I am concerned that if it blows, there will be collateral damage.

 

[JDW]

I've had waves/ripples visible just after boot on my Mac512, but that was fixed when I replaced the caps on the motherboard. But I've never experienced ripples on an SE/30. If you measure the 5v and 12v lines off the external floppy connector and get close to 5.0v or 12.0v when booted, then the source of your trouble is mostly likely the flyback. I'm sure those ancient caps on the analog board could use replacing, but in my experience they are typically not the source of trouble (as bad caps are on the logic board).

I'm not an expert on flybacks though, so I cannot say what will occur if yours blows. The very fact it is cracked makes me wonder what cracked it in the first place. If one contends it was "age alone" then I would expect to see such cracks as a widespread problem, but your report is the first I've heard.

If you're worried (and don't care to conduct a scientific experiment to see what happens when a flyback does blow), then you either have to replace the flyback or your entire analog board.

 

[techknight]

that fly is gone.

You could try repotting it with corona dope and see if it helps, but ultimately you will end up replacing the flyback. The reason for the glow is because the air is ionized around the windings where a crack/short has occurred. the transformer will get hotter than normal too.

 

[JDW]

But why would it have cracked in the first place? Because the machine was bumped and tossed around too often?

 

[techknight]

or more likely the plastic around the flyback is degrading with age which is causing warpage/cracking.

I restore old tube style TV sets, and i see this all too often.

Best thing to do is corona dope/beeswax it. Then see if it goes away, and how long it lasts. may last 5 minutes, may last 5 or 50 more years. never know.

 

[tt]

I think the flyback has finally failed. Last night the CRT blacked out and I could get it back after some light tapping, but it would not stay on. I tried refreshing the solder joints at J1 and the flyback, but it did not help. Any thoughts on the probability of the flyback vs other issues?

 

[Mk.558]

I figure we all are going to be seeing a rise in analogue board issues, we already have issues with PRAM batteries and capacitors, but eventually parts on the analogue board will fail along with the PSU. It'd be nice for the "used to be a TV tech" comrades to pitch in a general troubleshooting guide for us all. We already have the site from Japan about SE/30 issues (downloaded to disk in case it goes down), but I'll assume there is more that could be mentioned.

 

[tt]

Yes, that's a good idea. I was looking at Tom Lee's repair guide, and it shows approximate resistance values between windings in the 128K/512K/Plus transformer. Would the SE/SE-30 transformer be similar? He also mentioned the transformer is a poor design choice, I wonder if this is also the case for the SE transformer? Could there be an alternative replacement component and one that is perhaps even better suited for the design?

 

[Mac128]

Almost any transformer is a better voice than the stock oem. Larry Pina details the suitable replacements. I assumed Tom lee did likewise ... Either way, the 128K/512K analogue board is equipped with traces for a larger more robust transformer, which ais n almost universal recommendation in our community, along with a complete re-cap ... Finding he parts at this point may be a bit of amchallenge considering how little demand there is to even preserve an old CRT, much less new ones ...

 

[tt]

I didn't see alternative part numbers. All I have seen so far is listings of part numbers Apple has used in the past designs. Do you have a list of the alternative part numbers?

 

[Mac128]

Not sure there is an alternative part number list. But they are all inter-compatible. What you want to do is use the latest compatible transformer with your Mac. I believe the latest compatible transformer for the 128K is the SE/30. The Classic may work, but if so there is a CRT compatibility issue with some of them. Since the exact part number is not likely available any longer, an equivalent part would be desirable ... again assuming you can find it. Sadly it's not as easy as it used to be, even 5 years ago ...

I believe JDW has an excellent spreadsheet for the compact Mac replacement components, but can't remember if it includes the transformer ...

 

[techknight]

for awhile, a bunch of NOS flybacks got dumped on ebay. I managed to nab one before they all went gone.

How to restore flybacks and prevent inter-winding arcs, fill in cracks, etc that arnt already carbonized.

You need a vacuum canister with hot wax under an electric griddle or flame to keep the wax hot. Dunk the flyback into the hot wax and pull a vacuum. the air inside the flyback will fill itself in with wax, and moisture will get baked out, and of course wax will fill in cracks.

This will prevent moisture damage and fix corona discharge issues as long as it isnt already carbon tracked.

 

[CC_333]

The Classic may work, but if so there is a CRT compatibility issue with some of them.

I thought the incompatibility lied only in the yoke; the CRTs are the same across all the compacts (including the Classic/Classic II). Therefore, a flyback from a Classic should also be the same, right?
Same CRT=same flyback?

I suppose there could be differences in the flyback-to-analog board interface, but why?

Anybody care to confirm or debunk this "theory"?

c

 

[techknight]

yes, the yoke is not directly interchangeable without some persuasion.

but ive swapped CRTs keeping the original yoke and sliding it onto the other CRT without issues.

since its black and white, you could do this very freely.

Color CRTs, its a pain in the ass to switch out CRTs and keeping the same yoke. you have readjust purity and reconverge. FUUUN

 

[tt]

I don't think the flybacks for the Classic and the SE series are compatible. The classic flyback has more pins (10 + 1) than the SE analog board (8 + 1).

Also, I don't think the flybacks for 128k/512k/Plus are forward compatible (at least physically due to a smaller pin layout) for an SE analog board. However the 128k analog board has provisions for a larger (presumably SE) flyback in the board layout. Here is a photo of JDW's 128K analog board: