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Dual 504 turntable overhaul help needed

klamsoss

klamsoss

Be willing to fail and try again.
Good afternoon race fans!
I've got a Dual 504 that seems to be having a slight issue with the timing. It works well, and sounds good, but after a few minutes, the speed picks up a bit. It's barely noticeable but it's definitely real. It's like it's running at 32 rpm and once it's "warmed up", it kicks up to the full 33&1/3 after about 6 or 7 minutes. I figured I would pull it apart and replace caps and see if there was anything obvious causing a problem.

I've got it apart, and I know the "black box" is where the few capacitors it may have would reside (I plan to just replace anything that is replaceable in there... resistors, caps... whatever I see. Passive electronic components are cheap, and I want this thing to last.). My question for the AK braintrust is:
What else should I do while I'm in there? It's already had the RCAs replaced with some decent quality ones...
This is a semi-auto turntable - the motor is automatically triggered by lifting the tonearm off the rest. place the needle over the record and lower the tonearm lever to drop the needle. When the side is over, the tonearm lifts automatically, the lever goes back to "up" position, and the record stops. No further automation than this, so no changer mechanism or auto-restart mechanism. There are some automated parts in there which presumably could use a clean and lube... but I don't know what items would need grease/oil or what kind of grease/oil to use. I've been unable to find a useful service manual for it. that explains the process of lubing the mechanisms.

Many thanks in advance for any help you all can lend!
 
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@lini thank you! Bavarians can always be counted on to do things properly, and the beer ain't bad either.


A lot of these lubes aren't available anymore, but there are suitable replacements out there. Some quick google searching leads me to the following substitutions:

For the renotac, I can use pretty much any 10w-40 oil or chainsaw oil, correct?
viscostatik - 10w-30 motor oil
alvania no 2 - any good quality white lithium grease
isoflex PDP 40 - singer sewing machine oil
silikonol AK 500,000 - any silicone based oil with APK of 500,000

Would you agree with my substitutions?

Many thanks!!!
 
@lini :bowdown:

many thanks. I have suitable fluids on hand... I used an especially long-lasting but thin bike chain oil in place of the disputed light oil PDP40. I saw that many use singer sewing machine oil, and then, chatting with a bike buddy about it, he mentioned that his mom used to use a light bike chain oil on her machine.o_O go figure! Motor oils for the othersI didn't have white lithium grease or silicone oil on hand, but since it worked before, I figure I'll do those points when I get it back. I'm just trying to correct this timing issue before sending it up to my sister in New York. Her Philips turntable is in need of much more attention...
Anyway, I've lubed it up.

But then when I flipped it, put it back in the lower case, and plugged it in.... I get nothing...
I've tried a few things:
If I flip it over and then move the arm to start it, I get a hum from the motor, and the central spindle spins but no motion on the belt or platter. I also get a small spark below the motor start capacitor when I am moving the arm to either the on or off position.
If it is standing on it's side and I move the arm to start it, the central spindle spins, NO hum, but still no action on the belt or platter. Same situation as far as the spark goes, but the spark is smaller.
Upright, I get nothing. No spark, no hum, no spinning... nothing

To me, this says there is a contact issue in the starter box, and there is also an issue with the motor connecting to the drive belt.

I hope I haven't ruined my spare 'table, and the one that my girlfriend likes better....:yikes:
 
You mentioned bike oil; Phil Tenacious can sub for the thicker Renotac stuff. It's like chainsaw oil too, quite tacky. I have used it on spindles and some other applications.
 
Okay, so I've read a few threads and looked a little further into it. And I'm thinking my next course of action is:

take the thing apart, really clean it out well, including all the stuff that I was going to leave for later (sorry sis... you're just going to have to wait a bit), and then reassemble. I wasn't planning to take all of the automatic mechanisms apart, just clean them as well as possible while still in place, using isopropyl alcohol and/or a citrus based solvent.
take the motor apart and really CLEAN the bearings out well, and re-oil with light mineral oil.
Slip the belt off and make sure the platter spins freely without the belt being on there.
Reassemble the motor and put it back in place, give it a few solid thumps with a screwdriver handle, and then try things out again.

If I don't get any action on the platter, which I kind of expect will be the case, what do I do next?
I'm also at a loss for what to do about the switch? relay? (that might be the wrong name for it... it's where the capacitor is mounted and appears to be where the mains come in and are then connected to the motor), which seems not to be working when the 'table is right side up, but DOES seem to work when the 'table is upside down.:confused:
 
Here, the "relay" or "switch" is the black box with the yellow capacitor inside. I took that cap out and it measured 0.124 and it's supposed to be 0.068. So I replaced it. That's all I've done, but now the switch no longer seems to work unless the turntable is at least on its side.
 

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I've had a similar problem on a Dual, possibly the same model, with the switch not operating when right side up. I can't remember what exactly I did to fix it but I did.

It could be caused by the arm activating the switch having been distorted by age and gravity or heat generated by the motor. With the table right side up try manipulating the lever, switch etc to see what will cause it to work. Even loosening the box and trying to coax it closer to the arm.
 
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happy to report that after a bit of fiddling, and properly positioning the belt, I have a freshly lubed, consistent speed, great sounding Dual 504.

I think I was a bit ham-fisted when i put the motor back together and the pitch adjustment is non-functional. I think I jammed the little expander plug in there too far, or didn't put enough oil on it for it to smoothly move in and out. The speed is slightly fast right now, but not by much. I'll fix that issue at a later date. For now, I'm spinning some Beach Boys and liking the sounds.

A big THANK YOU to all who helped! :beerchug:
 
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