Denon DP3000 dual capacitor replacement

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Hi all,

I have a denon DP3000 turntable. I've replaced the electrolytics after having some speed stability issues and now all seems well. However, there is a large electrolytic cap in the motor drive that is somewhat unusual - its one of those old dual section caps. This one is rated at 250V, and has 3.1uf and 1.3uF sections. Now I know that I won't pick up a direct replacement. But assuming you were replacing this, how would you approach making the right values?

The cap in question is shown in yellow highlight below - I believe it's function is to compensate for 50 or 60hz (the switch shown there allows you to switch form 50 to 60hz on this TT). I'd like to replace the cap given its age (must be nearly 50 years old now).

Thanks in advance

fran
 

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PRR

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...there is a large electrolytic cap in the motor drive that is somewhat unusual - its one of those old dual section caps. This one is rated at 250V, and has 3.1uf and 1.3uF sections.....

Why do you think it is electrolytic?? Especially in 1972, motor-run caps were more often "oil" (paper with oil soaked in).

And in hi-fi use, these rarely go bad. Even in refrigerator use, they sometimes run steady for 40 years. So why mess with it?

As Rayma says, IF it is open or drippy, PP is good modern stuff. (And don't lick old cap oil; wash-up well after cleaning-up).

> I believe it's function is to compensate for 50 or 60hz

Actually, because AC motors will not start to spin on single-phase power (they don't know which way to start spinning, and even if they come to speed they run rough and weak). Like a single-cylinder steam engine may not self-start (only worse). The cap "fakes" a 2nd phase for "2 phase power". Two steam cylinders about right-angle phase will always self-start.

The ideal cap value depends on line frequency. If you are sure this platter will never leave 50Hz-world, you can omit the global-market 2-value switch and use 4.6uFd (or 4.7- it's not hyper-fussy). If you think you may ever sell it to me in 60Hz-world, I wish you'd put a "50Hz only!" note on the bottom.
 
Thanks PRR.

You might well be right on the capacitor type. It measured perfectly (for capacitance, didn't try ESR mid you).

However, I replaced it with PP types last night and all is good. I kept the option to switch it even though I think I will never sell it (it was a gift). I paralleled some 0.68uF and 2.5uf to give me very close to original values.

Just to add in here in case someone is searching for this info in years to come. I also had a look at the motor bearings. They are oilite types top and bottom, and you can dribble a tiny amount in along the spindle for the top sleeve and for the bottom you can remove the bottom grub screw which serves as an adjustable bottom plate that the thrust ball bearing sits on and add a little oil that way. Its handy to not have to split the motor. Mine were certainly dryish looking, but the motor shaft was clean. Take note of the position of the bottom grub screw before removal to get the spindle height correct on reassembly. You;ll need to add a little thread sealant on the grub screw to stop it leaking.
 
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