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Speed accuracy on vintage belt drive TT with "electronic speed control"

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Posted on January 13, 2017 at 23:02:46
JoshT
Audiophile

Posts: 6622
Location: Eastern Massachusetts
Joined: July 4, 2000
I have a Philips AF877 table, which was built in the late 1970s. It is belt drive with electronic speed control (the subsequent AF887 had quartz lock control, but not this one). I bought it on Craig's List for $49 a few years ago for a second system and I think it sounds great.

I just downloaded the Turntabulator app on my iPhone and it showed the average speed initially as 33.16, which is 0.5% slow. I left it spinning and checked about every 15 minutes over the course of about an hour, and the next three readings were 33.13, then 33.14 and then 33.13 again. So, between 0.5% and 0.6% slow. The app does not test for variations - only average speed over about a 15 second period.

In John's post below, he and others reported observing the average speed of belt drives increasing over time, most likely because of bearing lubricant viscosity. But I gather that I should not expect that kind of a change on my table since it has electronic speed control built in (and claims to have a self-lubricating bearing in any event)?

This table also has pitch adjustment, but even the smallest adjustment brings the average speed above a +0.6% deviation, so that's not a "solution". Any sense of whether a technician could micro adjust the speed control? The service manual is on Vinyl Engine, but I can't make sense of it because I'm not electronics-smart! It's really an academic question because I really enjoy what I hear, but I'm nevertheless interested.

Finally, and perhaps more importantly from a performance standpoint, are there any apps out there that measure the stability of the speed as opposed to the average accuracy? It would be fun to see if the table is in spec as I have the owners manual from Vinyl Engine.
___
"If you are the owner of a new stereophonic system, this record will play with even more brilliant true-to-life fidelity. In short, you can purchase this record with no fear of its becoming obsolete in the future."

 

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RE: Speed accuracy on vintage belt drive TT with "electronic speed control" , posted on January 14, 2017 at 01:10:52
PAR
The speed adjustment on this turntable is specified as +- 3% which should cope with the slow speed you note. However that range is pretty wide and was probably not expected to cope with the user wanting adjustments of 0.5% hence it is fairly crude.

The speed variation is controlled by the knobs on the plinth but these, in turn, relate to variable resistors on the circuit board inside. The variable resistors should be set to centre position which may or may not help if they are not.


The belt may also have stretched over time and although the speed error noted should be correctable by the controls, a new belt might bring things closer to what you want - only trying it will establish this.

As for a speed measurement app that gives variation details I suggest the Dr. Feickert Platter Speed. You do need a test disc with a 3.15kHz tone. One may be bought from Dr. Feickert from Germany. The app is now only supported on i-phones and if you take the paid for option the application will calculate and display wow and flutter figures. There is an old free Android version on the web ( not via Playstore) which will give speed stability figures and max/min variations for the test period.

At the end of the day we are dealing with a $50 turntable and performance at the level of what were once called "transcription" turntables should realistically not be expected. It is not just a question of vintage status as true high performance turntables from as far back as the 50's and 60's command much higher prices for a reason.

 

RE: Speed accuracy on vintage belt drive TT with "electronic speed control" , posted on January 14, 2017 at 03:10:11
I agree with what Par says however I do understand your desire to tweak to perfection. One thing I would add to Par's list of things to look at is in addition to replacing the belt, make sure the drive spindle and platter drum have clean surfaces. Just for giggles wipe down the belt to remove any dirt. I know you said electronics are a foreign language but you may gain some with a a "tune up" of sorts. In the service manual (pg 6 of 17)there is a good description of how to set the voltages. After 50 years there is a good chance something may be off.
In all it seems you have a decent table the runs steady.

 

RE: Speed accuracy on vintage belt drive TT with "electronic speed control" , posted on January 14, 2017 at 06:03:28
rindolini
Audiophile

Posts: 584
Location: Munich, Bavaria
Joined: August 9, 2007
Josh: As you can see in the schematic, there's a trim pot (R495/497)in series to each of the pitch control pots (R496/498). So you'd simply turn R496 & R498 to the middle position each and then adjust the "base speeds" with R495 & R497, which are both located on the main pcb.

Given the age of the AF877, I'd suggest to turn both trim pots and both pitch control pots all the way a couple of times each for some "exercise" and then turn 'em all back to middle position, before you perform the actual adjustment. And as the motor control isn't quartz-referenced, you might additionally want to give it a bit of a warm-up before the adjustment (20 minutes to half an hour should do) - because without quartz-referencing there'll usually be some temperature-related drift during warm-up.

Greetings from Munich & have fun with your AF877 (*)!

Manfred / lini

*) Nice table - and one of the few belt-drives with actual platter speed sensing. Keep it out of direct sunlight, though - otherwise the bumpers of the hood will melt and leave a sticky residue. And direct sunlight would also increase the tendency of the case bottom to bend inwards, which the AFxx7 models unfortunately have - and which can even cause malfuntions, if it's bad enough...

 

RE: Speed accuracy on vintage belt drive TT with "electronic speed control" , posted on January 14, 2017 at 09:00:40
Lew
Audiophile

Posts: 10911
Location: Bethesda, Maryland
Joined: December 11, 2000
I would bet that you cannot hear a problem with that small error in platter speed, and especially because the speed stays very constant over time. IMO, if the speed is "very close" to 33.33, and if it is stable, you're good to go, unless you hear a deviation in pitch, which I guess is the definition of "very close". Just for yucks, you might want to check speed while actually playing an LP.

Rindolini really knows his stuff. The only thing I would add to what he and others wrote is that you might want to replace all the electrolytic capacitors with new ones, before you even do a speed adjustment. On the other hand, the cost of that exercise would exceed the cost of the turntable, unless you can do the soldering yourself.

 

Regarding your footnote (*) . . . , posted on January 14, 2017 at 09:01:33
JoshT
Audiophile

Posts: 6622
Location: Eastern Massachusetts
Joined: July 4, 2000
Yup! When I got the table, I noticed those two gooey blotches on the front and no remaining bumpers on the dust cover, so too late for that! Fortunately I saw a post on that on another forum and very gently washed off the goo without penetrating the paint. ;-)

I also read about the case warping issue. Fortunately I do not notice that and the table seems to sit nicely on its very small built in "feet".

It is indeed out of any direct sunlight and in a climate-controlled environment, and has been since I bought it about 5 years ago. Seems like the prior owner really liked it and took good care of it. I did have to gently wash it - particularly the rubber matt - to get the cigarette smoke smell off as he was an acknowledged "chain smoker". But it's a beauty now and smells nice, as a turntable should!


___
"If you are the owner of a new stereophonic system, this record will play with even more brilliant true-to-life fidelity. In short, you can purchase this record with no fear of its becoming obsolete in the future."

 

Thanks everyone! Slight update and a question . . ., posted on January 14, 2017 at 09:14:30
JoshT
Audiophile

Posts: 6622
Location: Eastern Massachusetts
Joined: July 4, 2000
So, with the benefit of a good night's sleep, I tinkered ever so slightly with the pitch adjustment nob and am now at a stable average speed of 33.26, which is within 0.2%. It did take about 20 minutes to gradually climb from 33.16 to 33.26, but then it held firm for about another 20 minutes before I turned it off. I'll give it a few more whirls throughout the day to see if it consistently performs that way. And I'll try with a record on it too, which I guess would also verify if the speed control is working as it should.

I will definitely clean the belt and applicable surfaces. And I'll also at least give the pitch adjustment nobs a full twist each way a few times to see of that has an impact. Seem like good ideas in any event, and might improve any wow and flutter? (Though I don't hear any.) As far as the internal electronic adjustments, I just don't dare try on my own, but will check with some friends to see if they'd be comfortable trying with me hovering to learn.

Finally, where would one purchase a belt these days that would safely be within spec and do no harm? Also seems like a good investment, even if only for the future.

Thanks again gentlemen, and I'll report later in the day whether I find any notable changes after performing the additional tasks!
___
"If you are the owner of a new stereophonic system, this record will play with even more brilliant true-to-life fidelity. In short, you can purchase this record with no fear of its becoming obsolete in the future."

 

RE: Thanks everyone! Slight update and a question . . ., posted on January 14, 2017 at 10:31:47
here is a whole page to look through.

 

Final update for now (I promise!), posted on January 14, 2017 at 13:34:48
JoshT
Audiophile

Posts: 6622
Location: Eastern Massachusetts
Joined: July 4, 2000
So, it held steady at 33.26 with a record on (plus the weight of the iPhone of course). The speed did not change when I put the tone arm down (I have a Shure M97x at 2g with brush down).

Just cleaned the belt and drive spindle and edges of the sub-platter - so all relevant surfaces - and it's now holding at 33.27. That was a great suggestion because the belt was kind of stuck to the edges of the sub-platter and everything was just a bit tacky to the touch. Probably more tar from the years of cigarette smoke. When I cleaned the power cord and interconnects for the first time a lot of brown gunk came off so It should have occurred to me to clean the belt. Thanks!

So, I'm proclaiming success with the average speed (knock on wood)!

I might test the wow and flutter in due course, and I'll get a couple spare belts for the future anyway.
___
"If you are the owner of a new stereophonic system, this record will play with even more brilliant true-to-life fidelity. In short, you can purchase this record with no fear of its becoming obsolete in the future."

 

LOL! Thank you sir, but I'm more inquiring about reputation . . . , posted on January 14, 2017 at 13:48:12
JoshT
Audiophile

Posts: 6622
Location: Eastern Massachusetts
Joined: July 4, 2000
I was more wondering if there are any dealers of choice or any to avoid. LPGear, who I have dealt with before and has a stellar reputation, sells them for $18.90 a pop. But the place called Vintage Electronics, also US-based, sells them for $8.00 each (and less if you buy 2 and even less if you buy more). The only other source I saw was a guy in Germany on eBay, who had even lower prices.

So, assuming the belts are either both original Philips or are both from the same aftermarket OEM source, I will go with Vintage Electronics for the far lower price, but neither site specifies whether they are actual NOS Philips belts or aftermarket. Should I assume the latter?

The only reason I'm at all nervous is that a repair guy once told me not to use aftermarket belts on a Thorens TD126 MKIII (another belt drive table with speed control) because he said they are all bad and burn out the motors.
___
"If you are the owner of a new stereophonic system, this record will play with even more brilliant true-to-life fidelity. In short, you can purchase this record with no fear of its becoming obsolete in the future."

 

RE: LOL! Thank you sir, but I'm more inquiring about reputation . . . , posted on January 14, 2017 at 15:23:58
John Elison
Audiophile

Posts: 23874
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since:
January 29, 2004
I bought a belt once from Turntable Basics for my Thorens TD-126 MkIII and it was twice as wide as the original. I wrote to Turntable Basics expecting them to exchange it, but instead the guy told me to take a razor blade and slit it down the middle so I would have two belts for the price of one. It sounded like he wasn't willing to exchange it or else he really didn't want to. Anyway, I built a little jig to keep the belt and razor blade in position as I dragged the belt through the jig and slit it down the middle. It actually worked very well and I ended up with two belts. Both of them worked just fine.

Good luck,
John Elison

 

Wow! , posted on January 14, 2017 at 15:50:59
JoshT
Audiophile

Posts: 6622
Location: Eastern Massachusetts
Joined: July 4, 2000
Silver lining and all I guess. :-)
___
"If you are the owner of a new stereophonic system, this record will play with even more brilliant true-to-life fidelity. In short, you can purchase this record with no fear of its becoming obsolete in the future."

 

RE: Final update for now (I promise!), posted on January 14, 2017 at 17:36:19
Travis
Audiophile

Posts: 6170
Location: La Grange, Texas
Joined: November 25, 2001
Take that stupid brush off your cartridge.


"If people don't want to come, nothing will stop them" - Sol Hurok

 

RE: belt quality, posted on January 14, 2017 at 17:51:02
rindolini
Audiophile

Posts: 584
Location: Munich, Bavaria
Joined: August 9, 2007
Josh: Probably aftermarket, I'd assume. But you probably needn't worry about that, as the AFxx7 family models aren't as sensitive in terms of belt quality as most other belt-drives because of the aforementioned DirectControl design.

I.e., on most of the other belt-drive designs with DC motor only the actual motor speed is sensed (if at all) and "processed" by the speed control circuitry, so that these designs have to rely on very good belt quality for a correct and constant transmission ratio as well as a comparatively heavy platter to provide a sufficient flywheel effect for low wow & flutter. Whereas the few belt-drive designs with actual platter speed sensing (first one as far as I'm aware was the Braun PS550, closely followed by Philips AFxx7 family (and its successors like for example the AF829(II)) and some years later the Dual CS750(-1)...) can compensate for somewhat lower belt quality to a certain degree and also don't necessarily require a comparatively heavy platter for good to very good wow & flutter performance (the DirectControl family models typically delivered ~ +/- 0.05 to 0.04 % (DIN, weighted) in magazine review measurements). Quite a clever concept - so that I'm actually pretty disappointed that manufacturers don't make more use of it in current models, especially as comparatively complex electronics would nowadays seem a lot cheaper and easier to implement than high precsion mechanics compared to the late 70s...

Greetings from Munich!

Manfred / lini

P.S.: Almost forgot: I'd guess for the speed adjustment using a strobe disc would be more convenient than using a smartphone with a suitable app.

 

Why?, posted on January 14, 2017 at 18:59:44
JoshT
Audiophile

Posts: 6622
Location: Eastern Massachusetts
Joined: July 4, 2000
It seems like there is a split among people who have done both. Of course it would be easy enough for me to give it a try.
___
"If you are the owner of a new stereophonic system, this record will play with even more brilliant true-to-life fidelity. In short, you can purchase this record with no fear of its becoming obsolete in the future."

 

Thanks!, posted on January 14, 2017 at 19:03:18
JoshT
Audiophile

Posts: 6622
Location: Eastern Massachusetts
Joined: July 4, 2000
I'll go for the Vintage Electronics - two for about $15.

I'm really enjoying reading up on this table.
___
"If you are the owner of a new stereophonic system, this record will play with even more brilliant true-to-life fidelity. In short, you can purchase this record with no fear of its becoming obsolete in the future."

 

RE: Why?, posted on January 14, 2017 at 19:40:44
Travis
Audiophile

Posts: 6170
Location: La Grange, Texas
Joined: November 25, 2001
I don't think there's anything good about it.

I noticed that you could hear the music before it played, like pre-echo. Not only through the speakers but you could hear it in a dead silent room from right off the record.

And, where is that dust going that it's "picking up"?

Nope, I learned my lesson with the Shure V15/Type V.




"If people don't want to come, nothing will stop them" - Sol Hurok

 

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