QRK 12C (Russco) Turntable Restoration Help & Guidance

[mcaddie7]

Hi all,

A few months ago I found a crusty old QRK 12C turntable which are guess are cousins to the famous Russco turntables? Basically built exactly the same so I took it upon my self to restore it. Was hoping any of you all that own and restored one of these chunky tables may be able to help.

TLDR: Need source an opinions on idler and rumble. It sounds great but you can hear it slightly when sitting next to table. Source for new idlers? The speed adjustment / torque screws, any tips with those? Are these tables only so quiet given the massive motors on them?

Upgrade so far include:

• Motor was completely rebuilt, and new delrin washers were added at both friction points. Motor runs pretty quiet now and gets quieter after a 10 minute warmup period.
• New shock mounts for motor board.
• Idler wheel was removed, and sent away. They trued it up and added rubber to outside (We'll get to this).
• SME 3009 added to the table. Hole cut out and arm added.
• Sound deadening added to plinth, turntable platter, and turntable chasis on underside to help add weight and reduce rumble.
• New plastic thrust washers added to idler spindle on top and bottom.
• Small delrin thrust pad and new ball bearing added to main platter shaft.

Now for my remaining issues / questions:

• I've seen people upgrade the "thrust" set screws for all 3 speeds. Should I use ball ended, should they be soft or metal, or should they be fine point? I imagine this helps with transmission of vibration. I bought these hoping the smaller contact point and a ball would make it less chattery?

• I don't like the job they did for my idler by leaving on old rubber and adding new. Does anyone have a source / sell a new one? for 5 months waiting and $160 I'm not happy with my wheel. The motor is quiet but when the idler is added into the picture that's where all vibration comes from.

I know that the new idler is true as you can see it, however if the rubber is hard or uneven underneath from the portion they did not remove, wouldn't that cause rumble?

• Any other tips for quieting this down? I can't build a new plinth but was thinking of adding MDF to the underside to add weight.

 

[Blackdog61]

My best advice is to read all the threads you can.
A few things I learned with mine:
-Rumble can be significantly reduced by getting the motor capstan adjusted to run as true as possible. Any wobble will be transferred to the idler which connects to the ankle bone, leg bone…………
-The tonearm should be mounted to a wooden armboard with a layer of rubber or deadening material between it and the aluminum plinth. I now have an arm mounted to the rear left corner of the plinth so it doesn’t touch the aluminum at all.
-I added deadening material to the aluminum plinth and underside of the platter.
-Careful attention to grounding helped quite a bit. Any EMI can transfer to the platter and come through as noise.
My Russco runs very quietly at normal listening levels.

 

[Blackdog61]

I read your post again this morning and think you are in good shape. I use a delrin idler which has a square O ring that I bought on the big E site about two years ago. It may not be available now. However, the old red one runs fairly well too with little difference in rumble. I think you should make an armboard to decouple from the aluminum plinth. That will yield the most improvement. Noise from the turntable which doesn’t make it through the speakers is just part of the deal.