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Beogram 1200 repair

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Dillen
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Dillen replied on Tue, Mar 7 2017 5:19 PM

Be careful using contact cleaner on Pertinax (the material the fiber board in the mains switch is made of)!
Pertinax was (back in the day) made from cloth and lacquer pressed hard together and, depending on
the chemicals in the contact cleaner agent, the pertinax material will soak up the fluid and turn conductive (coal-like in both look and feel) and
start smoking and arcing. Perhaps even catch fire - I don't know cause that's when the owner discovered it, carried the
Beogram outside, hosed it down and brought it to me the next day.
That was a Beogram 1203 and the contact cleaner was sprayed into the start relay housing, which also handles mains voltage and
contains insulation made from pertinax.

Rotate the switch back and forth (mains not connected!) a couple of times to break through eventual oxidation and it'll be fine.

Reoiling the motor is not an easy task. Do a search for sintered bronze bearings (or Oilite as they are often called).
Rudy (Beolover) did a post on his blog page showing how he did Beogram 4002 motor bearings - a job very much like this.

Martin

Søren Mexico
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Dillen:
Reoiling the motor is not an easy task. Do a search for sintered bronze bearings (or Oilite as they are often called).
Rudy (Beolover) did a post on his blog page showing how he did Beogram 4002 motor bearings - a job very much like this.

There is no way to "restore" sintered bronze bearings, you can clean them with whatever you like, cook them in oil, leave them soaked in oil for weeks, you will never be able to open up the microscopic holes in the bronze, When the bronze bushing run dry, the steel shaft starts wearing on the bushing, resulting in closing the micro holes. What we have now is a nearly normal bronze bushing (no more sintered) with seize marks or in worst cause circular stripes.from wear.

What I do is, clean the shaft with acetone, if there are bronze rest on it, clean with 60 micron 3M micro finishing sheet until totally clean and shiny.

I now clean the bushing.with acetone, then try the fit of the shaft to the bushing, if the shaft goes in very lightly and there is more than 0.1 mm play, the bushing is gone. If the shaft goes in kind of hard, dont force it. Roll an adequate piece of 60 micron around a smaller shaft or screw driver, rotate this inside the bushing (always parallel to the bushing, dont "wobble") clean properly with acetone and try with the shaft, it has to fit lightly without play, if still kind of hard, repeat with 60 micron until it fits properly. Now use a 80 micron paper and rotate it with light pressure 8-10 rounds, clean with acetone ad a drop of SAE 40 motor oil and you are good to go.

Instead of micro finishing paper you can use 400 grain and 220 grain water sandpaper.

The theory is that the bushing must be 0.03 to 0.05 mm bigger then the shaft to have space for lubrication. The last rounds with 80 micron will make parts of the bearing surface coarser and make space for oil to stay inside the bushing.and keep it there, Depending on use you may have to lubricate again after a year or 2.

I have done this on 2 BG50CD a BG 1000 and a BG 1202 and they are still working

I know there are other theories out there, but believe me. I have been working with printing machines and bronze bushings for more than 40 years.

Collecting Vintage B&O is not a hobby, its a lifestyle.

Menahem Yachad
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Martin

Thanks for that heads-up regarding burning pertinax.

I have been doing my procedure for years with no problems.

Upon reflection, I can only presume that the contacts were not cleaned correctly, and therefore residual resistance caused heat, which caused the burning.

Because I disassemble my switches completely (given that they are able to be disassembled), and then clean all the contacts with Brasso, until there is NO oxidation remaining at all, and therefore very close to ZERO ohm contact resistance, then there should be no heat build-up at all.

Nevertheless, I will look for a suitable Nye Gel contact grease, instead of contact cleaner.

BTW, Nye 868H FluoroCarbon Gel is excellent, for restoring the old sliding potentiometers on the 1970's BeoMasters.

 

Dillen
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Dillen replied on Wed, Mar 8 2017 7:00 AM

Menahem Yachad:

Upon reflection, I can only presume that the contacts were not cleaned correctly, and therefore residual resistance caused heat, which caused the burning.

 

No. The Beogram I told about above was not in use - it was just connected to mains when the
start relay started smoking.
The owner "repaired" it at the kitchen table during the day and in the evening it was sitting quietly on the shelf.
The owner noticed a smell and saw smoke billowing out from under the lid of the Beogram.
Pulled the mains and put it out in the garden.
(Actually I wrote about this many years ago, but perhaps it has gone together with the earliest Beoworld incarnation, because I cannot find it).

Different contact cleaners contain different chemicals, and I'm sure that it doesn't happen with
any and all contact cleaners (or we would have heard about it more) but it certinaly happened with
whatever type of cleaner this Beogram owner used.
The problem is, that the cleaner soaks into the pertinax material (they all do) and the
combination of the chemicals in the cleaner and the board material starts conducting.
At mains voltage (230V in Denmark), it doesn't take much leakage in the material to cause a problem.
The more current it conducts, the more heat builds up and the situation escalates.
The material gets darker and darker, - the above one was charcoal black and I could easily measure
conductivity through the material.

I have used several different contact cleaners over the years but have found Kontakt 60 to
be the best allround one. It evaporates reasonably fast and almost completely.
(But keep in mind, that no contact cleaner will ever remove anything, it will just losen
dirt and oxidation and allow it to shift around - and add a little to the mess each time).
I still keep it away from places with mains and pertinax board, though.

And Søren is of course absolutely right - we can repair all we can and will but we will never be
able to restore the bearings to "as new".
The best solution will always be to fit new bearings.

Martin

Saint Beogrowler
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Dillen:

The best solution will always be to fit new bearings. Martin

Is there a source for purchasing new bearings for these Beograms?

Peter-

Dillen
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Dillen replied on Wed, Mar 8 2017 4:50 PM

Peter:

Is there a source for purchasing new bearings for these Beograms?

That's the problem.
None.
- quite yet...

Martin

hwbd
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hwbd replied on Wed, Mar 8 2017 5:07 PM

Hello Everyone

(hope I am not hijacking or posting in the wrong thread apologies if I have)

I am new to beoworld and also new to B&O products.

A bit about me, I am originally from Ireland but currently live in Helsinki so getting parts from the UK/US is a little trickier than I'm used to at home.  I love tinkering with things everything from engines and motorcycles to small scale electronics. I also do some fabrication and machining from time to time so if necessary I can make parts for my latest purchase.

I recently bought a 1200 from ebay which is my first turntable. It was of course described as fully working. It is in good condition and everything functions how it should apart from the drive.

The drive I am talking about is the one seen in this video (not my video): https://www.youtube.com/watch?v=xJcLzOsWXiE

I have ran the motor without the idler wheel in contact and it runs fine nice and quiet. The platter bearing also seems perfect no strange noises or play. However when the idler is engaged with the motor drive cone it makes noise. I removed the idler wheel assembly and oiled the plastic bearings the shaft sits in but it still makes a rubbing noise.

From what I can figure out the noise seems to come from the speed adjuster tab rubbing on the ridge in the idler wheel. I don't know what this part is supposed to be like but the one in my player looks like a tab of some sort of copper alloy with a hole in the end. Is this right or should there be another part mounted in the hole?

Having not owned or heard a Beogram(or any TT) before I am unsure about how much noise it should make when running. At the moment you can clearly hear a rubbing noise in quieter sections of a record which is surely far too much noise?

Any help would be greatly appreciated

Dillen
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Dillen replied on Wed, Mar 8 2017 5:24 PM

You're right.
A fiber pad is missing at the outer hole (tip) of the bronze arm.
I like to cut a piece or two out of one the red fiber washers B&O used heavily for circuitboard mounting through the years,
glue it to the tab and file it down to size and shape.

Martin

hwbd
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hwbd replied on Wed, Mar 8 2017 5:30 PM

Thanks very much Dillen, I was really hoping it wouldn't be something too big. I might try and use a bit of nylon if I can't get hold of a fibre washer. I'll see what I can find

Was the pad on both sides of the bronze arm or just the top side? If anyone has a photo of one of these intact it would be great to have a look

Dillen
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Dillen replied on Wed, Mar 8 2017 5:37 PM

The pad will only carry the wheel on the pads upwards facing side, but the original pad went through the
hole in the bronze arm, so it protruded a little on the underside too.

Nylon is good but can be difficult to glue.

Martin

Menahem Yachad
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Usually, the rubber surround on the idler wheel is hard and dried out, and causes noise on contact with the brass pulley cone..

The speed will also be not 100% stable, because there is not sufficient stable friction between the idler wheel's rubber, and the brass pulley cone.

So, if you still have noise after replacing the tab, the idler wheel needs to be re-rubbered.

I use TerrysRubberRollers in the USA.

Menahem

hwbd
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hwbd replied on Thu, Mar 9 2017 3:59 PM

Thank you for the tips Menahem & Martin

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