[Dillen]

The “skeleton” sub-platter can be lifted off.
That would ease inspection.

Martin

[Dillen]

I looked through my notes, and I don’t have the measurements anylonger, but I
do remember my surprise experiencing the huge difference from foam to rubber, and
I also remember that the driver that was restored with foam was closer to the
(same) driver with original, old but intact surround than ones that were restored with rubber.

Another thing is, that the glue often supplied with new rubber surrounds usually won’t hold for very long.
It just doesn’t grip very well and, even after several weeks/months, you can often peel
the surrounds off again completely intact with no remains of glue sticking to them.
Most rubber surrounds are rubbish when it comes to finding a suitable glue (read: that is commercially available and not toxic).

Martin

[Dillen]

Does the relay make an audible click when the Beomaster goes in and out of standby?

Martin

[Dillen]

Has the center bearing come lose from the base plate?

Martin

[Dillen]

Sorry, I didn’t keep the numbers.
It was several years ago, but it should be easy to replicate for someone with time and means.

Martin

[Dillen]

Compare the T/S parameters of a driver restored with foam to one restored with rubber (both played in to losen up the stiff new surrounds),  and you will no longer
have any doubts.

I did exactly that.
I was expecting a difference but… oh dear, was I surprised.

Foam!

Martin

[Dillen]

jaspers1996 wrote:

Where’s that? Can’t for the life of me find a supplier in Belgium. Only option seems the be the one seller on eBay who charges 60 euros a piece now

Here.

Not in Belgium, though.

Martin

[Dillen]

Could be.
Or the supplied power is not clean, making the processor run unpredictable.

Martin

[Dillen]

I would check

-Power supply ripple (bad filter capacitors).
-DC on a speaker output (bad differentiel amplifier stage).
-Idle current trimmer(s) bad.

In that order.

Martin

[Dillen]

The warm amplifier section points to a bad idle current trimmer.
Replace the trimmers (there is one for DC offset as well) and adjust them as
mentioned in the service manual.
– Or grab a kit that also contains new capacitors and a slight upgrade to the signal path.
Kit here.
Other parts here.

Martin

[Dillen]

Two different tape drives were used in these autoreverse decks.
One type has a belt-driven tape motion sensor.

Martin

[Dillen]

I agree.
And for soldering in areas where vibrations are part of the
day (portables, car stereos, speakers etc.), I like to use solder with a hint of silver.

Martin

[Dillen]

Bad tweeter?
Mixed up orange wires for the midranges – or wrong polarization(s)?

Martin

[Dillen]

Don’t get me wrong, but if you cannot see your way out of removing the screws for
the bottom plate, you may want to consider if this repair job is for you.
Perhaps it would be better if you leave it to someone with experience and training etc.

Martin

[Dillen]

Keep in mind, that if you replace electrolytic capacitors with any other type,
the new capacitors ESR will be (often very!) different – typically lower, leading to
different filter characteristics (and potentially other issues).
In speaker crossovers this will in many cases require a new calculation of the
filters, as the ESRs (equivalent series resistances) will have been taken into account in the original calculations as the (frequency dependent) resistors, they are.

This is often the reason why owners experience, that their speakers sound “different” after changing capacitor types. The change in sound comes, not as much from the change in
type of capacitor, but from the fact that the filter properties were changed.

Removing a few ohms ESR in f.e. a series capacitor for a 4 ohms tweeter, makes a lot of difference!
– Also for the load put on the tweeter, – that may not agree that it was such a great idea.

The general speaker impedance etc. will also be different (typically lower!).

Martin

[Dillen]

Apparently a major malfunction.
Can you tell if something burned inside? – And what?
Wrong mains voltage setting?

Martin

[Dillen]

What Filip said.
And there is a convenient kit for the servo board for exactly this.
Here.

Martin

[Dillen]

Capacitors, capacitors and capacitors.

Martin

[Dillen]

It will need a rebuild. They all do by now.

New electrolytic capacitors. Replace like for like type-wise.
New trimmers incl. adjusting.

Martin

[Dillen]

The end switch should not be reached at the end of playing a record.
It should only be reached if no record is found.

End of record is indeed optically sensed using the ruler.
Has the main board been rebuilt with new capacitors, trimmers etc?

Martin

[Author]

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