How fast should a PS-500 platter get up to speed?

Alle Braun HiFi-Plattenspieler ab dem PCS 5
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beatcomber
Neuling
Neuling
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Registriert: 09.09.2019, 14:04
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How fast should a PS-500 platter get up to speed?

#1 Beitrag von beatcomber » 27.09.2019, 05:13

Greetings from the USA!

Please forgive me for posting in English - I'm afraid I do not know the German language very well.

I recently acquired a very rare 1971 Braun PS-500 made for the North American market (60hz strobe, etc.). Because Braun turntables are so rare in the USA, there is almost no information available in English, so I would appreciate some guidance, if you would be so kind.

My concern is the platter takes longer to start spinning that I think it is supposed to. It takes about 5 seconds to get up to 100% speed, which is a lot slower than what I see on YouTube demo videos of the PS-500. The good news is, once it gets up to full speed, it runs fine (and sounds terrific).

These are the steps I've taken to try fixing it:

• replaced the original belt with a new one from Thakker
• cleaned the motor drive, belt pulley and sub-platter rim with isopropyl
• re-surfaced the edge of the idler tire with sandpaper and cleaned it with isopropyl
• added some light oil to the platter bearing, idler spindle and pulley spindle - they spin very freely

I do not believe that the motor is the problem. It doesn't get excessively hot, and the platter is still slow to start even after being used for several hours. I believe that something in the drive system is slipping.

Any advice or insights would be greatly appreciated. Danke!

zbyszek
Jungspund
Jungspund
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Registriert: 27.02.2014, 23:52
Wohnort: Krakau, Polen

Re: How fast should a PS-500 platter get up to speed?

#2 Beitrag von zbyszek » 27.09.2019, 12:38

Hi,

I would check if the idler wheel tensioning is okay. The on/off button draws a string that tensions the idler wheel spring.
The service manual available in German has useful diagrams.
The idler wheel is properly tensioned when there is a 0.5-1.0mm space between the idler wheel and motor pulley, when set to 78rpm speed.
It cannot be too-light. However, a too-tight tensioning will cause audible rumble. It takes some time to get it right.

That string is easily broken so be careful during adjustment. It is a typical radio scale string and can be easily replaced. In my ps500, I installed a small pulley from a discarded cassette tape in place of that wire loop it goes through. The on/off operation is now much smoother and the string will not snap.

Also, light oil for the platter bearing is not a good Idea, as it is an inverted bearing. It will simply leak out, and possibly react with and destroy the plastic elements below the subplatter.
Use a black molybdenium grease like Molytex EP2. It is very similar to the black Molycote BR2 that was originally used.
Just stuff some of that grease into the bearing (after cleaning it) and mount the subplatter. The excess grease it will come out through an overflow hole on the side of the spindle.
PS500, CD4, T2, CSV 13, Regie 501k, Regie 510, L60

beatcomber
Neuling
Neuling
Beiträge: 4
Registriert: 09.09.2019, 14:04
Wohnort: Massachusetts, USA

Re: How fast should a PS-500 platter get up to speed?

#3 Beitrag von beatcomber » 27.09.2019, 13:11

zbyszek hat geschrieben:
27.09.2019, 12:38
Hi,

I would check if the idler wheel tensioning is okay. The on/off button draws a string that tensions the idler wheel spring.
The service manual available in German has useful diagrams.
The idler wheel is properly tensioned when there is a 0.5-1.0mm space between the idler wheel and motor pulley, when set to 78rpm speed.
It cannot be too-light. However, a too-tight tensioning will cause audible rumble. It takes some time to get it right.

That string is easily broken so be careful during adjustment. It is a typical radio scale string and can be easily replaced. In my ps500, I installed a small pulley from a discarded cassette tape in place of that wire loop it goes through. The on/off operation is now much smoother and the string will not snap.

Also, light oil for the platter bearing is not a good Idea, as it is an inverted bearing. It will simply leak out, and possibly react with and destroy the plastic elements below the subplatter.
Use a black molybdenium grease like Molytex EP2. It is very similar to the black Molycote BR2 that was originally used.
Just stuff some of that grease into the bearing (after cleaning it) and mount the subplatter. The excess grease it will come out through an overflow hole on the side of the spindle.


zbyszek, thank you so much for that extremely helpful information!

I suspected that the idler tension could be the source. The string on my PS-500 did break soon after I got it, and I have replaced it. I will re-adjust the tension and see if that fixes the problem.

Thank you also for the advice/warning regarding the platter lubrication. I will clean and re-lube it per your recommendation.

I'm going on a trip up to Montreal tomorrow morning, so it will be at least a week until I can work on it, but I will definitely post a follow-up as soon as I have a chance.

THANK YOU!

zbyszek
Jungspund
Jungspund
Beiträge: 19
Registriert: 27.02.2014, 23:52
Wohnort: Krakau, Polen

Re: How fast should a PS-500 platter get up to speed?

#4 Beitrag von zbyszek » 27.09.2019, 13:28

I forgot to mention, that the idler string tensioning should be done in the Off position.
PS500, CD4, T2, CSV 13, Regie 501k, Regie 510, L60

beatcomber
Neuling
Neuling
Beiträge: 4
Registriert: 09.09.2019, 14:04
Wohnort: Massachusetts, USA

Re: How fast should a PS-500 platter get up to speed?

#5 Beitrag von beatcomber » 27.09.2019, 18:04

zbyszek hat geschrieben:
27.09.2019, 13:28
I forgot to mention, that the idler string tensioning should be done in the Off position.
Thanks again! :thumb:

beatcomber
Neuling
Neuling
Beiträge: 4
Registriert: 09.09.2019, 14:04
Wohnort: Massachusetts, USA

Re: How fast should a PS-500 platter get up to speed?

#6 Beitrag von beatcomber » 12.10.2019, 20:57

FOLLOW-UP:

I checked the idler tension, and it was within the .50-1.0 mm tolerance referenced by @zbyszek, so that wasn't the problem.

I next turned my attention to the sub-platter and the inverted bearing. I cleaned out all of the black goo (the original Molycote BR2), as well as the oil I added, with some isopropyl alcohol, and applied some white lithium.

The slow start-up problem is now fixed!!!

:danke:

I realize that white lithium is not Braun's specified lubricant, but it's the closest thing that I have handy. I will get some black molybdenium grease and re-lube it. :thumb:

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