some manufacturers don't recommen ultrasonic. I've stopped using my AT ultrasonic cleaner. If you want I can sent it to you (30 years old, owes me nothing). I use a square of magic eraser and lower the sylus into that then brush gently. That clears all but the hardest crud.
OK, thanks - I'll PM you. I used a magic eraser today and it seemed to work well. Now both decks are good.
I stored my records in 8 aluminium DJ boxes until they started getting mouldy. It appears as patches on the record and if the sleeve is paper (without coating) it can also get grubby. I spray window cleaner on the sleeves and quickly wipe off. Dry by a heater. The mould dies. Sunlight on the covers seems to also kill the mould and bleach it away. I now have them in a cabinet where a bit more air can get around them. I use record spray off ebay then a duo pad, then another velvet to buff the surface. Some take several goes.