Forum Replies Created
-
AuthorPosts
-
Did you try the method stated in the service manual?
Martin
The interesting video is the bad one. I simply can’t see if the belt scrapes on something
– or the motor pulley, it can also scrape on the motors metal bracket (bad motor mounts).Martin
Where in the world, apprx.?
The scraping sound could come from the belt rubbing on something.
If you run the deck without the platter, the belt could run on the subplatter flange.Or it could be from the record sensing mech.
Have you tried with a record on the platter?Martin
The three locks must be rotated a little using a wide-bladed screwdriver, enough to allow
the subplatter to pass.
They will usually move in “loud chunks”.The belt will come off, and you may have to take off the black plastic surround to get at the
motor pulley to put it back (renew it and the motor mounts while in there).Martin
The “skeleton” sub-platter can be lifted off.
That would ease inspection.Martin
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
Does the relay make an audible click when the Beomaster goes in and out of standby?
Martin
Has the center bearing come lose from the base plate?
Martin
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
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
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
Not in Belgium, though.
Martin
Could be.
Or the supplied power is not clean, making the processor run unpredictable.Martin
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
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
Two different tape drives were used in these autoreverse decks.
One type has a belt-driven tape motion sensor.Martin
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
Bad tweeter?
Mixed up orange wires for the midranges – or wrong polarization(s)?Martin
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
3 December 2023 at 10:52 in reply to: Restore or upgrade Beolab / Beovox Penta Crossovers MK1 vs MK2 #34222Keep 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
-
AuthorPosts
