Having a problem with one of my 1210's... I'm pretty sure it's a tone-arm issue. Basically on records with large bass-lines / deep grooves, one of my Technics will produce an ugly muddy bass, as if the stylus isn't properly sitting in the groove. Both of my decks have IDENTICAL set-ups: identical height, weight, anti-skate; identical needles, slipmats, hardware etc-- it's all the same, as a control. I've swapped the needles around multiple times to cancel out the possibility of it being a cart/stylus problem.
So I'm guessing the only thing it can be is my tone-arm... but this is the one part of a table I know next to nothing about, nor how to fix it. I'm guessing it's something to do with its tightness, or the bearings? I've taken two videos anyway, so you can clearly see what is going wrong.
In the beginning of this video you see my first deck (the fine one), and the large bass line plays fine, without any nasty audio problems. The tone-arm and needle handles it great. (And yes, I know my speaker set-up is hardly ideal at the moment... this is changing on the weekend, and besides, it's clear that this is an isolated and specific problem with the second deck).
More detail in this one, especially when the platter is rotating slowly. You can very clearly see that the entire tone-arm shakes, wobbles, and vibrates when playing the deeper/wider grooves (i.e. the bassy parts). So much so in fact that it basically skips along the record at a low speed. You can see it very clearly in action on certain 3-4 second segments of the above video.
So, in short: how do I fix this? I'm hoping it's not a serious problem with the tone-arm assembly or bearings. I know there's a horizontal and vertical screw to be tightened on the tone-arm, but after gently changing both (both clockwise and anti-clockwise), I don't see much difference.