Thought I'd crosspost this to see if I could get any help for this issue. Hey all. Quite new to posting here, and still learning about older audio equipment, with my first and current stereo setup being comprised of (except for a Dayton subwoofer) vintage gear. I recently came across a Marantz SR 3100 receiver which seems to be a lesser known model and not all that highly regarded among others that preceded it in the marantz line.. however for $40 in its decent cosmetic condition I was okay with buying it to see if it would work out for my secondary PC/Headphone-use setup. The first step I took was a thorough cleaning of all contacts, pots, switches, etc as per the usual with getting an unserviced, uncleaned unit secondhand. Main tuner lamp is blown, but that's actually not a problem at all at the moment, with it being left on constantly, and with it being at my desk, I quite like not having the light glaring in my face My first impression after getting it was quite displeasing, and after playing a familiar record through the phono input, I was faced with very, very, very heavy distortion in the left channel, with deeper bass totally decimating any semblance of sound quality coming out of my left speaker. Right channel was quite nice actually. And the weird part (to me anyways) is that the headphone section seems absolutely perfect. No issues whatsoever with the sound and it is quite a respectable upgrade over what I had my PC running through previously. So off goes the case and covers again, and went at a second cleaning with everything I could think of throwing at it, including a second go at the switches, with special care to be very thorough in working the Deoxit in adequately. I replaced the fuse which was just a crudely cut copper tube crammed into the fuse cap.. And I worked each pot, switch, input, speaker terminal, to see if I could fix the issue. This helped a little bit. One note is that enabling the loudness switch exacerbates this issue quite a bit, which makes sense I suppose. So where I'm left now is with a left channel that is still underperforming and sounding a bit off at certain frequencies with a static-y sort of sound; as well as that bass distortion, only at higher volumes now. The issue only comes through both sets of my speakers, which are all 8Ω. A service manual hasn't been easily available on the usual sources, but I did find one for the SR5100 which is very similar in look as well as internally. I got some info from the 5100 manual but not much that I could use in my troubleshooting. Worth repeating, the sound through headphones is very nice and smooth, and might even sound better than my current primary stereo receiver, the Onkyo TX-2500 MK II. I have never recapped a receiver, or done any sort of internal electronic part replacement on one, but I reckon I'd be up to it if I could narrow the problem down to a certain area in which to replace parts.. One could hope it'd be that easy..