I received a Denon DP-80 today from Japan, it was supposed to be completely functional but it has a somewhat weird issue that seems to be speed control related and happens both with and without quartz lock engaged.
Both speeds seem a bit jittery, and the motor makes a sort of rattle / knocking sound. There's no weird noises spinning the platter with the power off. The strobo looks mostly ok, but it seems a bit jittery and on the rpm phone app the speed it shows keeps fluctuating about 0.3 rpm. Somehow that doesn't seem to completely show in the W&F it measures, maybe because of weighting, because it still gives readings under 0.10%, which while not acceptable for a DP-80 doesn't seem as bad as it should be. While the phono apps are not really reliable and mine has started showing the speed constantly 0.3rpm too slow even with a turntable running perfect 33.3rpm, the W&F measures seem to still make sense. Both my well functioning Denon DP-3000 and Sony TTS-2500 show 0.03%. I also checked the DP-80 using a strobe disc but it was not as easy to see the small jittering as with the built in strobe, but I think I did saw it jump occasionally.
Here's what it sounds like, this was recorded with my phone under the motor unit as it was running. The sound is not super loud but it's not faint either, it's very clearly audible next to the turntable. Never used jumpshare before but I guess it should be ok...
The file you are looking for does not exist.
jumpshare.com
So here's where it gets a bit weird... if I gently hold my finger against the mat or the edge of the platter to give the system a little bit of drag to fight against, the weird sound stops and the strobe starts looking stable, speed doesn't fluctuate anymore in the app either and it gives a W&F reading of 0.05% which seems quite good actually under those conditions.
It was supposed to be working properly but clearly isn't, which is a bummer but as it is cosmetically in quite nice shape and I was planning to give it a full service anyway I figured it's probably a bad cap or transistor and nothing to worry about... however as I opened it up it became instantly clear someone had been there already, the foam under the motor had been removed and replaced with cushions and then taking a look at the PCBs most transistors and caps had already been changed along with variable resistors VR1 & VR2... luckily the person who did this seems to have marked each replaced component with a little green dot. It seems the notorious 2SC458 have been replaced with 2SC1815 which I think should be fine, most electrolytics seemed quality Nichicons. Work seems generally clean, so maybe I wouldn't be dealing with someone else's hack job, but the bad thing is assuming that, since most transistors and caps have already been changed, the issue might be something more severe... It's possible this was originally worked on because of the speed issues and they didn't manage to repair it changing components.
Things I have tried so far - adjusting the magnetic head, didn't seem to make any difference except when the gap got to about 0.4mm reception started to get spotty and speed would occasionally run away for half a turn or so. I don't have a scope but I have adjusted VR2 to get 45rpm on the variable mode with the speed dial at the middle point, then VR1 to dial in 33rpm. Both pots were smooth in operation, as it should be since they have been already replaced...
Any ideas? I got this through proxy service from Japan, I don't think the auction seller was specializing solely in audio and it wasn't claimed to be "perfect" but they did advertise it as no problems in normal use, which is not the case, so I should have a good case for a claim. The proxy service does have buyer protection for non-junk items and I have 7-days to make up my mind. I could try to troubleshoot this more thoroughly during that time frame but not sure there's much I could do without a scope and I don't think I should bring a solder iron to it if I intend to send it back.
EDIT: found a thread on diyaudio where the problem seems quite similar
https://www.diyaudio.com/community/threads/denon-dp-80-stutters-on-33-but-ok-on-45.414265/ - it seems it was a transistor issue in that case. That I could deal with.
