SE FDHD suspected flyback transformer failure

[xantufrog]

Hi all,

I recently acquired an FDHD the other week, and by and large it runs great. The "cheese gear" was bad of course, so I fully cleaned and rebuilt the floppy drive.

I do, however, have a concern that my flyback is failing. I've attached an image here and you can see corrosion/leakage on the left near the base.

The symptom is that periodically the screen will pop, flicker, and/or distort. One time I got a "bomb" popup as it froze. This seems to occur mostly after initial startup - once it's warm the machine (so far) seems stable and happy to run for hours.

No battery leakage, mainboard seems clean.

Thoughts, and advice on best path forward? The other thread I saw on this showed a successful flyback replacement from an NOS kit, but it seems dangerous and hard to come by

Thanks for your guidance!

 

[xantufrog]

and as a follow-up: if my best option really is a new analog board, am I correct that a "regular" Mac SE board is perfectly fine for my FDHD (earlier year of manufacture, but I don't think they changed anything on that side of the hardware)?

 

[desertrout]

The symptom is that periodically the screen will pop, flicker, and/or distort. One time I got a "bomb" popup as it froze. This seems to occur mostly after initial startup - once it's warm the machine (so far) seems stable and happy to run for hours.

Hard to know for sure, but I'm tempted to first suspect cracked solder joints on the flyback and possibly elsewhere on the analog board (on the headers specifically) - that flyback looks okay to me. Especially since the symptoms seems to go away after the machine warms up (expansion improving connectivity). If you're even remotely comfortable with a soldering iron, reflowing those joints is a quick and easy task, see what happens.

 

[xantufrog]

Hard to know for sure, but I'm tempted to first suspect cracked solder joints on the flyback and possibly elsewhere on the analog board (on the headers specifically) - that flyback looks okay to me. Especially since the symptoms seems to go away after the machine warms up (expansion improving connectivity). If you're even remotely comfortable with a soldering iron, reflowing those joints is a quick and easy task, see what happens.

that's encouraging! I'll start there and report back. I'm also tempted to apply some of this to cracking in the yellow gluey stuff at the top of the flyback: https://www.amazon.com/dp/B008OA7CA...5ANIO9GX&psc=1&ref_=list_c_wl_lv_ov_lig_dp_it

(after safe discharge of course)

 

[xantufrog]

Hard to know for sure, but I'm tempted to first suspect cracked solder joints on the flyback and possibly elsewhere on the analog board (on the headers specifically) - that flyback looks okay to me. Especially since the symptoms seems to go away after the machine warms up (expansion improving connectivity). If you're even remotely comfortable with a soldering iron, reflowing those joints is a quick and easy task, see what happens.

It looks to me like the solder joints are great. I also don't see any bloated or leaking capacitors anywhere. Here are some close-ups of the concern on the flyback. I will try a reflow, but given how mint everything looks otherwise (purely ignorant, though I am) I'm a little doubtful I'll see improvement

 

[desertrout]

I strongly advise against this. The material at the top of the flyback is a sort of epoxy / wax sealant, and can't be reflowed.. and I honestly do not think it likely your sealant is an issue here, it looks fine to me. It naturally dries out and turns brown over time and with use, which is what you're seeing and it's perfectly normal. In fact, it actually looks pretty good (better than most I've seen) with still much of its original 'yellow' colour. Some folks have attempted to improve this seal or 'reseal' using silicone and/or corona dope, but unless you are sure of what you're doing and why you're doing it (i.e. you know that the flyback is actually arcing - which you can see and often smell - smells like ozone, very noticeable), I don't recommend it. One is likely to do more harm than good, potentially ruining a possibly good flyback (which are difficult to find).

I still recommend reflowing the flyback joints and the other joints on the headers to the logic board and neck board first (labelled J4 and J1 respectively), even though they may look fine to the naked eye. The cracks are often not visible. Rule that out as a potential cause first. As part of this procedure I'd recommend using contact cleaner on the J1 and J4 header and connectors as well to clear up any possible corrosion.

It's also worth noting that near-40 year old capacitors can fall out of spec without showing visible signs such as bulging or leaking, or sometimes leaking is not visible until the cap is removed. So if the solder reflowing doesn't solve this, I would then recommend checking your voltages and start performing more thorough diagnostics.

But reflow those joints first. Leave the flyback alone unless you know for absolute certain it is the cause, and to me your symptoms do not suggest the flyback. Not yet.

 

[xantufrog]

I strongly advise against this. The material at the top of the flyback is a sort of epoxy / wax sealant, and can't be reflowed.. and I honestly do not think it likely your sealant is an issue here, it looks fine to me. It naturally dries out and turns brown over time and with use, which is what you're seeing and it's perfectly normal. In fact, it actually looks pretty good (better than most I've seen) with still much of its original 'yellow' colour. Some folks have attempted to improve this seal or 'reseal' using silicone and/or corona dope, but unless you are sure of what you're doing and why you're doing it (i.e. you know that the flyback is actually arcing - which you can see and often smell - smells like ozone, very noticeable), I don't recommend it. One is likely to do more harm than good, potentially ruining a possibly good flyback (which are difficult to find).

I still recommend reflowing the flyback joints and the other joints on the headers to the logic board and neck board first (labelled J4 and J1 respectively), even though they may look fine to the naked eye. The cracks are often not visible. Rule that out as a potential cause first. As part of this procedure I'd recommend using contact cleaner on the J1 and J4 header and connectors as well to clear up any possible corrosion.

It's also worth noting that near-40 year old capacitors can fall out of spec without showing visible signs such as bulging or leaking, or sometimes leaking is not visible until the cap is removed. So if the solder reflowing doesn't solve this, I would then recommend checking your voltages and start performing more thorough diagnostics.

But reflow those joints first. Leave the flyback alone unless you know for absolute certain it is the cause, and to me your symptoms do not suggest the flyback. Not yet.

Wonderful guidance, thank you! I'll leave it be and cross my fingers a reflow does the trick

 

[xantufrog]

I'll see if it is still doing it after reflowing all the joints by hand on the analog board, as well as those linking the little floating board that attaches to the crt and the analog board

 

[xantufrog]

Really hope I'm not jinxing myself here, but thanks fir your guidance the other day on my Mac SE FDHD screen popping issue. I cleaned the corrosion off the flyback (presumably just a cosmetic effort) and reflowed all the major solder joints on the analog board and the little screen neck board. I also replaced the grinding tired fan with a Noctua while I was at it. So far for a few days it's running stable image (and much quieter). Time for some classic gaming

 

[desertrout]

Ah, good to hear! I need to grab some Noctuas...