Does anyone have any experience on using these modulators for TV use ? They were widely used in home computers, prestel units and simple pattern generators, channel 36 only and UM1286 does sound as well. As I had a couple of these hanging about, I thought I'd make up an RF output for a Freeview box I picked up for 50p. I couldn't find a full datasheet for it anywhere, so I made up something like the circuit from the BBC Micro, it seems to work OK for vision but tuning for sound is critical and caption buzz is also an issue. I suspect this is something to do with the fine tune input which sets the sound spacing (I think). I wondered if anyone has had success with these, here is a picture to show you what I mean, there were also RS versions too;
Frank, that link brings up a message stating that the website is temporarily unavailable and has been like that all day but if I just go to alldatasheet.com, it works normally but doesn't return any results for UM1286 (although it does have several for an ADUM1286 IC but, as these are '3 kV RMS Dual Channel Digital Isolators', they aren't much use!)
It did the same to me after I had posted the link last night, wasn’t me honest.
I downloaded the two page document and virus scanned it but it’s a PDF so cannot post it in the forum. It isn’t a schematic just the technical specification and pin out, it’s also very poor quality but it is legible.
I can upload the file to Chris but not sure if Chris would want to have another sites work, or I can email it to anyone who wants it.
The link is still down, I had tried various google searches for UM1286 and usually nothing of much relevance turns up. I used to have a paper RS datasheet but I can't find it anywhere. its 5746 in the index.
Thanks for all the efforts, the datasheet is just what I needed. I think the relevant information is that the fine tune input needs to be set at 3.2V to ensure sound carrier appears at the correct 6Mhz spacing. I've used a resistor, but might try a diode clamp to see if it provides any improvement to the audio.
I don't have Photoshop and just used Paint.net to adjust brightness and contrast with some additional tweaking in MS Paint, a technique I've used to to tidy up several schematics in the past but the level of grey in this was a step to far for my simple methods!
