I got this Harley Benton DC Junior a few years ago and it's been my main axe since.
Only issue is it has the worse tuning stability of any guitar I've owned, Not only going out of tune but getting it to correct pitch can be spotty in the first place.
Any ideas for replacement tuning machines? I've already replaced the nut with a graphtech one a while back and it only slightly helped when tuning up. I also don't mind drilling new screw holes if need be.
I have a Harley Benton too and changing the old plastic nut with a TUSQ got rid of like 50% of the problem, new Gotoh tuners did the rest: I can only recommend this brand, high quality at nice prices. And since a lot of their models come with ferrules both for metric and imperial, there should be no need to re-drill the holes. In any case always double check your measures.
I heard good things about Kluson too but I never tried them myself.
I put these on my SG recently. One of my stock tuners died and I couldn't find a replacement. I could have sworn I only paid $100... But maybe I just told myself that to feel better about the purchase.
Anyway, they're pricey, but easy to put on and they work nice. My only complaint is that the mounting plate looks like cheap metal. For that price you would think the plates would be polished. On the other hand, they're on the back of the guitar and mostly covered by the tuners anyway.
I forgot to mention, on the 3x3 Gibson style headstock, the string pull angle is not great on both your E strings, and to less extent the A and B and could be binding. Another thing that just popped in my head - I'm not familiar with that particular model, but if it's a bolt-on neck, make sure the neck is tight and not moving at all. Another place to check is the bridge and tail piece, I'm assuming it's a Tune-O-Matic style. Check if you're having binding issues at the saddles, and that the threaded inserts (bushings) in the body aren't loose - this happens on Gibsons and Epiphones as well. If that's the case, take the bridge and tail piece out and carefully wick in some super thin CA glue to help stiffen them up
Check some setup videos and see it's not your methodology, check the nut for binding, check that the bridge isn't moving and neck is both cracked etc. And if you've only had problems with one set of strings, try another set and preferably source.
I was going to change the machine heads on a cheap, ancient guitar but ended up taking them apart, cleaning and putting a little fresh grease on. Pretty quick job.