Forgive my question, BUT, with AV2, AV3, and AV4 available and working properly, do you REALLY need to have AV1 function as an input? It just seems unnecessary. You really need four inputs?
probably not, but its nice to have, would give me a challenge to try and work out how to get AV1 to work.
Certainly dont bin your DVD recorders. they may not be valuable now, but you wait, in 30 years time they will be a 'vintage' collectors item and people will be restoring and collecting them. I can guarentee that. You may have moved on to other things, but there will still be guys re-living the 2000's and restoring and buying up old DVD recorders. Even if no lasers are available now, some guy will start up a repair shop and get new aftermarket lasers made somewhere and it will turn into a big business. This happens with most things. people collect and restore anything. Its a bit like VCR's now. Many 'specialist VCR' guys doing repairs and restorations on those now. There is probably warehouses all over the world with NOS VCR parts just waiting to be un earthed.
I was just about to bin a old 1978 Pioneer tape deck the other week, well i was half considering it, as it needs new belts and last time i looked in 2002 you could not get them. Then i looked online and theres many specialist vintage tape deck shops restoring these sorts of decks and there is new belt kits all over ebay.
So please, do not chuck out any DVD recorders, epecially good brands. Sell it on ebay, amazon, craigslist, your local paper, this forum, or offer it for free. People will buy old stuff even if its just to get a few decent parts off it.