Dual 506-1 Speed Irregularity

[David_NC]

I was playing a record on my 506-1 a week or so ago, and I noticed it sounded like a slight speed slowdown every so often. I don't recall if it's every RPM or every 1/2 RPM or whatever, but watching the strobe confirmed it. The speed will be perfectly fine, the 'dots' on the platter edge will jump over to the direction indicating the speed is slow, and then return to normal. The slowdown lasts maybe a second or so. Imagine playing a record and then putting a finger on the platter edge for a second at regular intervals.
Before I dig into it or order a belt, I'm curious as to what could cause this. I suppose it could be a motor issue as well, but I hope it's something simple! Thanks for any ideas or suggestions.

 

[lini]

Hmmm... Did you already check, whether the little metal ball the Abstellschiene should run on is still present?

Oh, and did that problem occur regardless of the position of the arm on the record, or did you rather notice it near the end of the record?

Greetings from Munich!

Manfred / lini

 

[Yahgn]

Hmmm... Did you already check, whether the little metal ball the Abstellschiene should run on is still present?

Oh, and did that problem occur regardless of the position of the arm on the record, or did you rather notice it near the end of the record?

Greetings from Munich!

Manfred / lini

+1

 

[David_NC]

Hmmm... Did you already check, whether the little metal ball the Abstellschiene should run on is still present?

Oh, and did that problem occur regardless of the position of the arm on the record, or did you rather notice it near the end of the record?

Greetings from Munich!

Manfred / lini

Hi,
I have no clue what the 'Abstellschiene' is... is it the end of record lift / power off trigger that has a bearing under it? If that's it, no, I haven't checked that. It does the irregular speed thing the moment it's switched on regardless of the tonearm position. Thanks.

 

[NoTransistors]

Manfred likes to sometimes be a joker. The German language is a bitch for us Americans.

 

[David_NC]

Manfred likes to sometimes be a joker. The German language is a bitch for us Americans.

LOL yeah, I was kinda wondering. It's bad enough having to worry about the 'Dual Pimple' and trying to explain to others that it really exists and that it's just a German thing! It did get me wondering about that slider thing with the bearing, though!

 

[NoTransistors]

No one expected these things to last decades. Watch those balls. Do I hear that AC/DC song coming on?

 

[nbarber]

Last week I fixed a 506-1 that had a similar problem. Pull the platter (English instructions can be found at The Vinyl Engine) and lube the platter bearing. Depending on the age of the belt it may be worth replacing it while the platter is off.
I use "Liquid Bearings", a light viscosity,synthetic oil with a nice applicator that can be found on Amazon. Once everything is back together let it run for a while.

 

[David_NC]

No one expected these things to last decades. Watch those balls. Do I hear that AC/DC song coming on?

Who didn't? I expect things to last pretty much until they are obsolete! I've been fortunate that almost every piece of equipment I've owned has done this.

Last week I fixed a 506-1 that had a similar problem. Pull the platter (English instructions can be found at The Vinyl Engine) and lube the platter bearing. Depending on the age of the belt it may be worth replacing it while the platter is off.
I use "Liquid Bearings", a light viscosity,synthetic oil with a nice applicator that can be found on Amazon. Once everything is back together let it run for a while.

I'll check it, thanks. Do you have a good source for belts?

 

[NoTransistors]

No matter where I get a belt from, it is more often than not a poor replacement. Belt drive Dual are very finicky.

 

[David_NC]

No matter where I get a belt from, it is more often than not a poor replacement. Belt drive Dual are very finicky.

I'll spend a bit of time on it this week. I'd like to get it straightened out soon, as it's a decent sounding 'table. Besides, once I get my 1219 working properly, I'm sure I'll have minimal interest in the 506, which means it'll likely sit in a non-working state!

 

[lini]

Seth: Not really - I just didn't happen to know the exact translation at that moment (sometimes Dual's translations appear a little oddish to me... (*)) and was in a bit of a hurry, when I wrote that reply. But I expected David to have already downloaded the service manual, so that finding the Abstellschiene (= switch off rail (part number 215 in the explosion drawing) - so in this case it's a pretty literal translation...) in the parts list should have been no problem for him (or at least that's what I assumed...).

Greetings from Munich!

Manfred / lini

*) And also not necessarily consistent. For example, the "switch off rail" in the combined service manual for the 505 & 506-1 in the service manual for the 1254 is translated as "shut-off rail" instead - whereas it's Abstellschiene in both cases. Hence using the original German terms wouldn't seem such a stupid choice to me, as these would seem pretty consistent - even if these sometimes would appear to be odd choices even in German, like in the case of the infamous Steuerpimpel (typically translated as "control stud" (Huh? What???)), which I would rather have called Kupplungskäppchen and translated as "clutch cap"...