HV Flyback Transformer

[hackerb9]

So, my IBM 5155's screen started pulsating at me (larger, smaller, larger, smaller) and I'm pretty sure I recognize the syndrome from my MacPlus: the flyback transformer is about to blow.

I seem to recall hearing "life hack" tips like, "Stick epoxy on the outside" to keep a flyback transformer working, but I was wondering if anyone here had ever tried anything like that? Any success? Or, any reason it would be a bad idea?

I think my first step will be cleaning out the anode cap and putting some heat sink compound under it to prevent discharge. (It might be an old wives tale, but it did seem to help my MacPlus.)

Anyone know a good source for replacement 5155 flybacks? (I hope they're not as hard to find as it was for the MacPlus...)

 

[Hugo Holden]

The probability of the flyback transformer in the 5155 monitor being the cause of your fault is nearly zero.

You don't need to put epoxy anywhere near anything.

It is a daft idea to put "heat sink compound" under the anode cap, unless you are referring to what was heat sink compound in the 1960's and 1970's, which was purely clear silicone grease used on mica insulating washers.Even then, there is no need to add it.

The flyback transformer is not "about to blow" and this emotive language makes no scientific sense at all.

I know the IBM 5155 VDU like the back of my hand and could draw out its schematic in my sleep.

If you care to post a video of the defect, I can make some suggestions about where to look for the problem.

Smaller and larger display suggests fluctuating power supply voltage to the monitor. The power supply for the IBM 5155 VDU is unique and there is a special sub-system for in in the computer's smps, see page 17 of this article:

https://www.worldphaco.com/uploads/T...WER_SUPPLY.pdf

I would be looking there first after checking the supply connections.

 

[Timo W.]

It is a daft idea to put "heat sink compound" under the anode cap, unless you are referring to what was heat sink compound in the 1960's and 1970's, which was purely clear silicone grease used on mica insulating washers.Even then, there is no need to add it.

To add to this: modern heat sink compound is conductive, so that idea is not only daft but highly dangerous. When it comes to HV, don't try things you have heard somewhere.

Make sure the anode cap and its surroundings are clean and you're fine. There's nothing else to do there.

 

[VERAULT]

i agree and doubt the problem is a bad flyback. regardless of what youtube says they dont fail thst often. they do however becaude of thier weight cause broken solderjoints and sometimes cracks on the pcb around there they are mounted but i doubt thsts a problem on the 5155. the psu on thr 5155 is terrible and a cause of many problems. certainly was for me.


and lets agree to never say or make mention of "lifehacks" again.. there is too much complete bullshit being spewed on the internet as is. leave that nonsense for the facebook people.