THis assumes you have a working flyback transformer of the same type. Fine if there's somebody else with the same machine and the test gear to make the mesurements, less fine otherwise. Let me re-state the question. The horizotnal output stage was designed once (I do not beleive for an instant that they simply tried random numbers of turns and random component values). The horizontal output stages of just aobut all manufacutrers seem to follow the same basic sort of design. So presumably there is a way of desinging them. But I can't find any book or web site that explains it. Is there one? [Suppose IU wanted to make a nrew CRT-based monitor. How would I set about designing the horizontal output stage). Knowign how to design such a stage, I think it would be possible to come up with a suitable flyback transformer -- not necessarily an exacy copy of the original, but one that would workl -- for a defecting machine. Flyback transofmresw are almost always potted for insulation reasons... and what do you mean by 'primary winding' (and how do you indentift it on the core)? A lot of flybacks had a multi-tapped winidng connectinfg to a suppl line through a diode; the collector of the output transistor; maybe a diode or diode/capacitro to ground; various +ve and -ve outputs (via diodes/capacitors), etc. I think tryuing to find the apporpirate bit of that wininf if you've cut through the transformer would be hard to say the least Have you tried this? I am wondering just waht sort of vacuum is needed for this. YEs, I've wound plenty of coils that way. But coils that have to stand high voltages are a little harder. You need to be careful that you don't ahve turns next to each other with a large votlage betweent them, or you will get breakdown. It's a related problem to widing RF coils (where you don;t want turns with large RF voltages betwene them due to stray capacitance effects). You my well need to put the turns down in a particualr order. I am not convinced this is the whole story... -tony

Thanks, I will take a look at said references... -tony

Strange... I've found the detailed characteristics of flybacks from different monitors to be very different. And if you're not lucky, you need a supply of output transistors ;-) Alas not all classic computers run at TV rates (GGA). For example I was using a composite video monitor yesterday with a 22kHz horizontal scan rate. I have no idea where I would get a replacement flyback for that. I remember (just) whem there were sort-of generic TV flybacks that could be used in may sets by connecting them correctly. And the ont thing that was emphasises was that it was the inducatance, not the resistance, that mattered (both of the flyback and of the yoke). In any case the DC resistance of most ohizotnal deflection coils used in transistorised monitors is a lot less than 1 ohm, and therefore diffiuclt to measure with any accuracy. Scheamtics are not normally the problem... As I think is well-known on classiccmp, I prefer to do things myself rahter than to get somebofy else to do it. Not just for cost and enjoyment reasons, but also because if nobody carries on this sort of thing, the knowledge could be lost. I have a homemade one based on a design published in 'Television' magazine in the UK (back when said publication actually had useful stuff in it). IIRC it's a 4011 chip running as an oscillator driving a power transistor that energises the primary winding of the flyback which has a capacitor connected across it to resonate it. You look at the riinging waveform with a 'scope (_any_ 'scope). A good flyback rings, one with shorted turns is massively damped. This is, alas, not a complete test. It will not pick up shorted HV rectifiers inside the flyback. And some colour monitor flybacks have a 'diode split overwind' (the EHT winding is in several sections with diodes conencted between them). It will not detect shorted diodes or inter-widing shorts there. But it does a good job most of the time. THose can sometimes be repaired. Alas many of the machines I work on have totally encapsulated flybacks (sometimes, i nthe case of colour monitors, also including a thick-film unit with potentiometers to set the A1 (G2 to you) and focus voltages. That's the sort I am wondering about how to replce. In some cases, they never were available as an individual spare parts (only as the complete PCB), so finding a spare is going to be impossible. I would have to make one. -tony