It's not clear from your description if the rumble is coming from acoustic feedback (through the air or turntable plinth) or from the mechanical parts that make up and run the platter. I think you're leaning toward the latter as the source of the noise but I'm not sure.
Besides the motor & its mounting, have you changed the idler wheel? Rubber parts can become hard with age and this will transmit a lot more noise. The spindle for the idler wheel could also be a source.
The platter bearing, spindle and spindle cylinder can also wear with use. If these parts are no longer to spec, the loose or irregular fit can cause low frequency noise.
The rubber wheel shouldn't cost a lot, but if the platter assembly itself is worn, you may be moving into "not worth it to fix it" territory. There are some pretty good performing current generation turntables that don't cost an arm to buy new.
Good luck with your search for a fix.
I believe the noise comes from the motor, idler wheel assembly as it disappears when I disengage the idler wheel. I think this eliminates the bearing and associated platter assembly, I have replaced the idler wheel itself but not the idler wheel spindle. I like the idea of having a fully automatic tt. Are there new ones worth owning? thanks Markus
There is still a possibility it could be the platter spindle assembly. When the idler wheel is engaged, it places asymmetical pressure at one point on the rim of the platter. This could cause rumble when the idler wheel is engaged.
The problem is that you don't have access to the original specs and tools used for quality control measurement. That leaves you to replace the parts one at a time, hoping the noise goes away.
As for replacing the whole turntable with a new automatic model, you'll probably want recommendations from someone more up to date on current brands.
Have you talked to them?
Good preamps/receivers from that era often had rumble filters to compensate for the inevitable lf noise. Why intentionally damage records with an automatic? Try a used Rega.
Jeff Dorgay just released issue 31 of Tone and he has a whole bit on Dual turntables titled "Fix my Dual" ... you should check it out. He specifically mentions the 1219. He has a couple of web sites listed you can go to, fixmydual being one of them.
Does it make the same noise when its in the plinth? I think they have a spring suspension.Anyhow,when some TT's are run on something solid instead of floating on the springs, the motor does amplify itself for some reason.If you could,try lifting it up of off the saw horses if you don't have the original plinth with the spring suspension,and see if it quiets down.Of course if it does it in the original plinth,then this wouldn't apply.The idler wheel may be hard,or some other rubber parts mentioned above.
Also if it does this in the plinth,make sure it is floating free without touching the plinth.If it is bumping the plinth,that could cause a problem too.
Thanks for all the good info. Very interesting idea about the platter bearing being loaded with the idler wheel. There is a slight oscillation in the frequency of the noise. Bill at fix my Dual has had this thing twice. It works perfectly and sounds great but he hasn't been able to eliminate the noise. If I wanted a Rega I would buy one. I will check the article in Tone. I actually have it sitting on the spring suspension on the saw horses. I think the hard rubber thing is probably the problem. It is 38 years old or so. The tt is floating in the plinth. thanks again for all the great input, Markus
This brings back memories of my first hi-end system. I was 16, and bought a Dual 1215-S turntable in 1971 I think it was, along with KLH 17 speakers and a Harmon Kardon receiver after studying Consumer Reports. The whole thing cost me about $300. A lot of lawns cut to pay for that system!
After I hooked everything I realized the table had both wow and flutter. Dual at that time was located in Mt. Vernon, NY, about 20 minutes from where I lived. I took the table there and told the service guy, an older German guy, that I just bought this turntable and it had wow and flutter. He sort of laughed at me, then took the table to the back room, and came back a short while later to say I was right. He replaced both the platter and motor. It was fine after that and ran well for years.
Thanks, that sounds encouraging. Maybe I will see the end to this problem. thanks Markus
I would replace the idler wheel or have the one you have restored. The rubber on them gets old and hard. Any flat spots will give a thump sound or rumble that can be heard in quiet passages.
I believe Turntable Needles has a program to restore old and worn idler wheels.
You could try Ebay too, but may not see much improvement...but send the worse one for restoration.
I have a Dual 1229. It's the same as a 1219, but with a strobe. I run this table everyday, and it's absolutely dead silent. I can't hear even hear the motor when it's running.
You either have a bad idler wheel, or the motor needs to be pulled apart and lubed. This is something I personally do every few years. I also keep the plater bearing set in synthetic grease and make sure the plater bearing race gets plenty of oil.
I have rebuilt many Dual turntables. Email me and I will help you sort it out. My Dual 1229 (I replaced the tone arm with a Grace 747), is better than my Garrard 301. Honestly, it's one of the best turntables I've ever heard.
I have a 1229 and a 1219. Both are dead silent. I can put a stethoscope on either while playing a record and cannot hear any rumble.
My 1228 on the other hand has a old, tired idler wheel and the rumble is apparent.