Idler drive running 10% too fast

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jordanc8
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Idler drive running 10% too fast

Post by jordanc8 » 15 Mar 2019 21:17

Hi, I'm new here and new to working with turntables. I recently acquired my parents' Sony HP-161 (I have great memories of this player from my childhood). It has been stored in a dusty, non-climate-controlled barn for several years. I've started cleaning it up and have it in a good enough state to play some vinyl. A few things don't seem to be working (like the auto function), but the most concerning thing is that it seems to be running 10% too fast. I noticed that a song I'm familiar with sounded too high-pitched, so I counted: 33 revs in ~54 seconds. Taking the platter off, I've learned that it is an idler drive, made by BSR. Any suggestions on how to fix this?

Spinner45
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Re: Idler drive running 10% too fast

Post by Spinner45 » 15 Mar 2019 23:32

Make sure the motor pulley is clean, no residue on the speed steps.
If it still runs fast, it's because the BSR's were mostly designed that way.

smee4
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Re: Idler drive running 10% too fast

Post by smee4 » 16 Mar 2019 00:18

As Spinner45 said, make sure the drive is clean. If it is still too fast, you can reduce the diameter of the drive pulley. Be careful to not remove too much material, but, wrap a small flat screwdriver blade with sandpaper and hold it lightly against the spinning drive pulley (on the step with the incorrect speed). Keep it flat to the surface as you want to do it evenly, and I repeat, only take the tiniest bit off at a time, and retest. You can't put it back :)

smee4
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Re: Idler drive running 10% too fast

Post by smee4 » 16 Mar 2019 00:19

Also keep in mind the speed is 33 1/3, not just 33.

AudioFeline
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Re: Idler drive running 10% too fast

Post by AudioFeline » 16 Mar 2019 04:03

Buy an electronic laser tachometer from ebay (they are cheap) or download and print out a strobe disk so you can measure the speed accurately.
Counting revolutions doesn't have the same precision.
Last edited by AudioFeline on 16 Mar 2019 04:48, edited 1 time in total.

Doug G.
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Re: Idler drive running 10% too fast

Post by Doug G. » 16 Mar 2019 04:06

Yes, it was fairly typical for less expensive tables to run too fast. In fact, in some cases it may have been done intentionally because music is more exiting, to most people, if it is slightly too fast rather than too slow. 10% is pretty extreme, however. :D

Doug

Spinner45
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Re: Idler drive running 10% too fast

Post by Spinner45 » 16 Mar 2019 06:01

smee4 wrote:
16 Mar 2019 00:18
As Spinner45 said, make sure the drive is clean. If it is still too fast, you can reduce the diameter of the drive pulley. Be careful to not remove too much material, but, wrap a small flat screwdriver blade with sandpaper and hold it lightly against the spinning drive pulley (on the step with the incorrect speed). Keep it flat to the surface as you want to do it evenly, and I repeat, only take the tiniest bit off at a time, and retest. You can't put it back :)
Sandpaper is not a good choice for such a task.
A much better material is emory paper of a fine grain.
It results in a nice smooth finish with less chance of increased rumble.

smee4
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Re: Idler drive running 10% too fast

Post by smee4 » 16 Mar 2019 07:41

Spinner45 wrote:
16 Mar 2019 06:01
smee4 wrote:
16 Mar 2019 00:18
As Spinner45 said, make sure the drive is clean. If it is still too fast, you can reduce the diameter of the drive pulley. Be careful to not remove too much material, but, wrap a small flat screwdriver blade with sandpaper and hold it lightly against the spinning drive pulley (on the step with the incorrect speed). Keep it flat to the surface as you want to do it evenly, and I repeat, only take the tiniest bit off at a time, and retest. You can't put it back :)
Sandpaper is not a good choice for such a task.
A much better material is emory paper of a fine grain.
It results in a nice smooth finish with less chance of increased rumble.
We tend to use the name generically. Wikipedia says "Emery paper is a type of abrasive paper or sandpaper" Fine grit wet&dry sand(emery)paper is what I have used.

empireboy
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Re: Idler drive running 10% too fast

Post by empireboy » 16 Mar 2019 18:14

Those 1970s era BSR idler changers typically run about 2% fast when up to spec. 10% sounds way too fast, however.

I would download a turntable speed app for your smartphone and get a better approximate estimate of the speed. Shaving the pulley is probably the most effective fix for the standard 2% speed overrun. But I wouldn't shave the pulley until you determine the cause of the 10% error, fix it, and also clean and relube the motor and main platter bearing so it is running at nominal speed.

I think BSR made the pulley steps intentionally too large in diameter so they will always run 2% fast. They use fairly low torque cheap shaded pole induction motors and relatively lightweight platters (minimal flywheel effect) so perhaps an oversized pulley diameter was a tradeoff they baked into the design to offset a stack of heavy records sitting on the platter, voltage line fluctuations and gradual aging of the low quality lubricants BSR used which become tackier over time as they turn into cement and eventually freeze the platter.

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Re: Idler drive running 10% too fast

Post by AudioFeline » 17 Mar 2019 00:04

Another consideration is that the BSR turntable is not great quality, even when it's up to spec. I know it has sentimental value to you.

The BSR does not produce detailed sound and will not be very kind to your records (even when you install a new styli). You will be able to get much greater quality (and enjoyment) by getting an entry-level turntable with a phono preamp, and plugging the phono preamp into the tape input into the Sony's amplifier.

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