Thanks Martin. In play mode, the left reel is totally free. Could the motor generate the flutter by itself?

Hard to say. It could cause a bit of wow I suppose, but with the large flywheel it has to accellerate and decellerate,
I doubt this is what you hear since you describe it as flutter.
In some cases, all it takes is one tiny little piece of dirt clinging on somewhere to spoil the fun.
I don't have a deck of this type at hand right now, but I seem to remember that the left reel
is expected to provide a bit of back tension (read: brake a little), to keep the tape tight against the heads.

For other readers;
- Wow is when the tape speed is not constant but instead a "vibrating" can be heard in the signal pitch.
This is often caused by dirt on the capstan spindle or a deformed pressure roller which is what pulls the tape.
- Flutter is variations in signal amplitude. In other words, the sound volume is not constant. It's very common
to see this affect mainly the treble response.
This is often caused by the tape not being kept tight against the tapehead(s). As the tape is pulled
from one end, it's braked a bit from the other end to prevent slack.

Martin

Okay, okay, then I was right at first. It is wow I suffer from, because the sound itself is excellent.

So the definition indicated above is wrong, and I was always right. Piano is definitely vibrating (let's say at about 5 or 6 pulses per second).

I checked the pinch roller and it seems to rotate normally. Its surface is matt and rubbery. Can one adjust the pressure? It's not clearly mentioned in the SM page (5-1), apart from a pin to bend and a spring to adjust. Will they get wrong with time?

Edit: I just don't get it, I've just made a piano recording, it's come out perfect, really perfect, CD-like! Then rewind, listen again, horrible!

???????

Jacques

Same result when I press FFWD with no cassette, I let it turn for a few seconds, then insert a cassette and the wow has disappeared. It comes back gradually after a while (say, one song).

Hi chartz

You have obviously determined that you have a “wow” problem with your tape deck and you have made the first estimates of the frequency – “5 or 6 pulses per second” which puts it at ±6 Hz.  I am not sure what service manual you are working with but there is a reference to the source of wow frequencies in the BC9000 manual which I have found to be fairly useful in the past – take a look at section 11.1.  A 6 Hz frequency is most likely to be related to the flywheel which is running at ±6rps.  Lower frequencies can be associated with problems at the idler wheel (5.2Hz), take up belt (4.5 Hz) and drive belt (4.3 Hz).  If you have a scope, try and determine what the precise wow frequency is and it might just get you closer to the problem area on your deck.  Otherwise, you can be shooting in the dark for a fairly long time.

If you are able to swap belts with another machine, I would give that a try as well.  It can be surprising to see what the effect of different belts is!!

Regards

Geoff     

Thanks Geoff.

Well I eliminated the belts which are new from Dillen.

I eliminated the flywheel by swapping them over with one from a known good Beocord.

The only thing left is the idler wheel, the frequency being indeed closer to 5 Hz than 6 Hz. But where could I get a good one? Is it part 12152, not identified clearly as idler? It is also very difficult to access!

Why is the piano correct after winding a bit forward, then degrading progressively until it becomes a hammond organ again?

Sorry for asking but I take it that you did try with a different tape ?
Is it a C120 tape ?

Martin

Dillen:

Sorry for asking...

Martin

Don't be Martin! Yes I tried different tapes, TDK SAX 90 and BASF CE II 90 NOS and a Sony HF-S 60, as well as a TDK AD 90. All tapes produce an excellent sound with extended treble (more so on the BASF and SAX of course) on these decks, in spite of the wobbly piano on this one. I dare say they are better than my Technics BX606, which is not a bad deck. I recorded, for example, 'Piece by Piece' by Katie Melua and the sound is fantastic! No C120 of course... the last time I saw one was 30 years ago!

Good.

- And you replaced the capstan/flywheel thingy, right ?
- It's not because the chassis has cracked near the capstan spindle bearing -
or the bearing itself, allowing the capstan to wobble a little under load ?
- Belt rubbing on the triangular metal plate ?
- Motor pulley not centered, lose, damaged or dirty ?

I suppose you've tried it all.

Martin

chartz

Just a thought, but is the wow frequency the same at the beginning of the tape and the end of the tape?  An increase in the frequency can indicate that there is some drag on the rewind spool and this will change as the spool rotational speed increases.  If the wow frequency is similar at the start and end of the tape, the problem is more likely to be related to flywheel and drive side of the equipment.

There are two "idlers" in the tape drive.  I refer to them as the single idler (one wheel) and the double idler with two connected wheels.  The idler referred to in the table of wow frequencies is the double idler with item number 12041.  The single idler only comes into play for fast forward operation.  The double idler is used to develop the slower take up speed and this can feedback onto the motor speed.

Regards

Geoff

Thank you Martin and Geoff for your thoughts.

Dillen:

I suppose you've tried it all.

Martin

Indeed Martin!

Pressure roller pressure ?

Martin

I don't know. How do you adjust this? It's not clear to me in the SM. I hope it's not a matter of bending something!

Chartz

If you are checking the thrust roller, I usually look to see that there is at least a small clearance between the roller arm and the tape head frame while the tape is playing.  If there isn’t any clearance, the roller arm is resting on the frame and cannot exert any additional pressure on the roller and capstan.  Then you will have to do some minor bending work to get the correct clearance.

If you do have some clearance in your setup, you can test the effects of modifying the spring pressure between two extremes by connecting the spring on the right hand side and then on the left hand side.  Measuring the actual spring pressure using a spring balance is much more fiddly.  If none of this corrects or improves the wow then you will have to examine the situation a bit more closely.

By the way, I thought that the service manual description for this procedure wasn’t too bad!!

Regards

Geoff   

Right then. Clearance is in good order (0.5 mm) and pressure is normal. Augmenting it makes absolutely no difference.

What's left? What is the 'assembler moment'?

Thanks,

Jacques

Assembler moment appears to be the slipping force on the clutch.  If it is set too low then you will get a lot of clutch slip.  I have tried to set this in the past by wrapping cotton around the pulley and using a pre-weighed stack of 20cent coins to develop the correct moment - so this procedure can be done at home.  I am not sure what effect a slipping clutch would have on the wow during playback.  Perhaps someone would clarify if the clutch is primarily used for fast speeds or whether it is an important setting for playback??

Regards

Geoff

Hello,

I quote Tim Jarman who was kind enough to give me a few hints,

"Check the brakes, there are three felt pads that act on the spool
carriers (best accessed with the cassette tray removed), they can get
gummed up with dirt and cause this sort of thing. After repair work they
can also get re-fitted wrongly, check this too. I assume that your
mechanical overhaul has included removing the spool carriers from their
shafts, cleaning away the horrible old grease and lightly re-lubricating
them? This is very important in all Beocords as stiffness here can cause
needless head wear.

If all this fails try re-finishing the record / replay head with metal
polish. A good hard rub will remove any ingrained contamination, after
that wash the surface well with head cleaner (IPA)

Best Wishes,

Tim"

All these steps were duly taken, but the problem persists. Anyway, the felt brakes weren't dirty at all (still white). Lubrication was fine... I did it anyway! The heads? Like new and very clean. I did them too anyway! Assembler moment didn't make any difference of course.

What's left then? Sometimes (okay, very seldom) the piano is very clean and stable, especially after some FF operation. Why? As a reminder, the belts are new and everything is very, VERY clean!

I can hear the scrap yard calling... 

chartz:

I can hear the scrap yard calling... 

Chartz

You mustn't use such foul language , everything gets fixed eventually.  Just wait for a quiet moment and strip the deck down once again.  It will probably turn out to be something very simple and it doesn't take that long to dismantle and reassemble.  If you want to do the unthinkable and throw it away, you can always post it to me

Regards

Geoff

Okay, sorry about the dirty words...

Anyway, I've just realized the capstan has some lateral play (rear/front but none left/right) in its bearing. The capstan itself looks fine but there it is. I'm not sure it's the source of the problem but... it's worth a try, isn't it?

Would anyone have a spare capstan bearing then?

Many thanks in advance!

Jacques

Hi,

Anyone please? I'm not far thinking I'll buy another one and scrap this one... It's a shame considering the time I've spent on it but if it must come to that... A Nakamichi or a Revox maybe...

I don't have a factory new bearing but I may ba able to find a good used mech. section, or parts from one.
I will look.

Martin

That's very kind of you Martin, thanks. By the way, the motor on my Beocord 6000 has finally given up the ghost.

It suddenly became very noisy, so I took it apart (a very easy task, fully reversible) to see the brushes had disintegrated! But I was impressed by the overall quality of its construction, especially the servo system which is missing on more recent, understand cheaper, designs. It was indeed capable of auto-adjusting its speed which remained constant under strain. Newer designs such as those supplied by B&O until 6 years ago are simplistic motors whose speed quite audibly lowers when 'play' is engaged. And... the old one was silent!

Cheers,

Jacques

Hello,

Apart from the noise, is it normal that the new motor slows down (you can actually hear it) when Play is engaged then?

The old one remained perfectly stable at all times. Also it seems that it will slow down across the tape length, as the old motor didn't. I checked the PSU and the voltage remains stable (14 V) when the motor slows down.

On my old Technics BX-606 the motor is the same and it doesn't slow down at all. 

Please, anyone?

Hello,

Well I've finally (thanks to everybody for your input) solved my wow problem.

An incompetent tech (?) had messed up with the deck at some point of its life... 

Three problems arose: 

- the double idler wheel bearing housing (part 12135) was cracked,

- the capstan bearing had too much play in it, which I attribute to a wrong oil choice, because the heads present very little use (no marks) and the pinch roller looks new too. 

- someone had forgotten to re-assemble the left guiding spring and ball (no, not me)!

I got (from another kind member) a good capstan bearing and I fabricated a left spring, but a real B&O (or is it Vortex?) one is due in soon!

Anyway there is no more wow, and the recording and playback quality are great, finally as expected. My only problem is the motor, which is noisy and unregulated—the original one was tacho-controlled, à la Beogram 8000. It does the job though.

I am now in the process of buying a near-mint Beocord 9000, so expect to hear from me soon again!

Jacques