exxos's Atari, Amiga & retro forum

I think the flyback transformer on my CM8833-II just died. I've not had it long.. since May but its had a fair bit of use since then.



No smell or pops... but the power light at the front is not on.

I found this

and i've ordered a new flyback transformer because even if thats not the issue having spare parts for these old guys is useful...

but i've never done a repair like this before. Anyone got any experience with this?

I don't think that you'll have much trouble. Relative to the stuff you usually do the soldering on CRTs is agricultural.

The biggest issue you may have is finding a reasonably large soldering iron bit so as to heat the legs of the transformer to get the solder out.

Having said that, not having the power light on doesn't sound like a flyback transformer issue, more PSU.

stephen_usher wrote: 25 Oct 2021 09:21 I don't think that you'll have much trouble. Relative to the stuff you usually do the soldering on CRTs is agricultural.

The biggest issue you may have is finding a reasonably large soldering iron bit so as to heat the legs of the transformer to get the solder out.

I'm more concerned with discharging the CRT safety if thats what i have to do. my soldering iron goes up to 450C and i can use hot air to preheat.

stephen_usher wrote: 25 Oct 2021 09:21 Having said that, not having the power light on doesn't sound like a flyback transformer issue, more PSU.

Agreed. But the noise is very flyback like....

On my 1048S, which I think is very much related depending on model, I changed the Flyback and HOT (Horizontal Output Transducer).
Old school TV tech told me these are the 2 common items to fail.
HOT is less than £5 so worth a shot.
Mine started to make 'lightning' on the glass just before it died. White speckles occasionally appearing before then.

Higgy wrote: 25 Oct 2021 09:34 On my 1048S, which I think is very much related depending on model, I changed the Flyback and HOT (Horizontal Output Transducer).
Old school TV tech told me these are the 2 common items to fail.
HOT is less than £5 so worth a shot.
Mine started to make 'lightning' on the glass just before it died. White speckles occasionally appearing before then.

I didnt get any warning. I was playing an MSX game and the screen just went black and it started to make that sound.

That said this is the exact symptoms.



And as you can see his power light does not come on either.

Either flyback or driver transistor blows. Normally a big one on a heatsink. Either way. Protection on the the thing normally stops you from even turning it on.

exxos wrote: 25 Oct 2021 09:46 Either flyback or driver transistor blows. Normally a big one on a heatsink. Either way. Protection on the the thing normally stops you from even turning it on.

Indeed otherwise the screen would be very dangerous to touch without the flyback.

I'm literally more scared of opening that CRT up and doing that repair than I am of putting an aeroplane with an engine failure into a field. Crazy. :oops:

terriblefire wrote: 25 Oct 2021 09:57 Indeed otherwise the screen would be very dangerous to touch without the flyback.

I'm literally more scared of opening that CRT up and doing that repair than I am of putting an aeroplane with an engine failure into a field. Crazy. :oops:

Just use a insulated object to pry the HT cap off and make sure you short it to GND.

We use to have a screwdriver with a lead connected to the chassis to short it out before removal. After that unsolder the flyback and check the big driver transistor (back then they were all BU508's).

Another good flyback repair video..