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Restoring a Beomaster 1000

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Jeppe
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Jeppe posted on Thu, Nov 17 2016 12:48 AM

This is my first post and I am almost completely new to BO! Having had some Tandberg and diverse Danish vintage equipment, I recently has become very interested in BO as well.

I recently bought two Beomaster 1000's. One with white keys and one with black. Both need restoration. I really want to make these work. I am specially interested in the earlier version with germanium transistors.

I opened the white one up today, and it seems a transistor was burned (marked AC128,3). There was black dust above it on the wood cabinet inside. I wonder if this is possible to replace..? Is there any hope?
There may be other problems as well, I don't know yet. But this seems serious.

Where do you find more rare spare parts for your vintage machines?

How wonderful that there was a little envelope on the inside with schematics inside it!


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chartz
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Answered (Verified) chartz replied on Thu, Nov 17 2016 6:25 PM
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Welcome to Beoworld!

And congratulations on your introduction to B&O's wonderful vintage products.

These Beomasters are nice items.

I for one always find the components I need on eBay. The aforementioned transistors are indeed listed there. Do have a look!

Those AC 128 germanium transistors are (were) quite common and not very difficult to find. There were tons of them used in old radios and tape-recorders.

Good luck!

Jacques

Søren Mexico
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When I start a new project, I go to Martin (Dillen on this forum) first of all, he can provide most of whats needed, then onto E-bay as Chartz

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

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Dillen
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Dillen replied on Sun, Nov 20 2016 8:53 AM

Most will know that Beomaster 1000 came in white and grey key versions but it was in fact produced in 12-14 basic versions.
Add to this several build series within each type, more than 30 for some types, and almost all had minor changes and revisions here and there.

I own 145 Beomaster 1000s (apprx 70 different - not counting woodsort variations) and my collection is far from complete, particularly when
it comes to export versions, but I've noticed minor differences even within the same build series and there were also some aftermarket revisions and service-related recommendations, that my or may not have been introduced.
Not everything was well documented and the service manuals are merely covering the basic types.
The included schematics would be the closest-to-correct reference but I wouldn't trust it blindly.

Martin

Jeppe
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Jeppe replied on Sun, Nov 20 2016 3:48 PM

145 BM's, wow!

The many variations, I see, I had an feeling this would be the case, but that many variations.. Makes the restoration all the more excitingWink

Mine came without speakers. I wonder what speakers they came with, and what speakers would be a good combination for them.. I just bought a pair of Beovox 2702's. Was originally looking for 1702's, but found these, newly restored and in a very good condition, like new. Not necessarily for combining with the BM1000, I was looking also for a BM 1001 and thought it could be a good combination.

May I make a recommendation by the way? I bought these 2702 speakers here: https://www.anapeachloudspeakerrestoration.co.uk/
The man behind this company, Andrew, is very nice to deal with and he often works with and restores BO speakers. I know he is working on a few new pair of BO speakers now.

rolfzetterberg
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The reason for the transistor confusion is that they have labeled one transistor wrong on the plan(not in the schematic).

Take a look here,the upper transistor is labeled correctly as  AC128-3, but the lower  wrongly has got the same number.That transistor should be AC126-5.

 


Søren Mexico
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I have restored several BMs and never had a drawing that was exactly as the unit, as for the BM 1000 I found 3 different schematics, and non of them were for the one I have here (black keys)

As for speakers, the 2702 will do good, the speakers recommended for the BM 1000 was the Beovox 1000 and the BG was the BG 1000.

I have the BM and the BG 1000 using Beovox 1600 (wall speaker) until I find a pair of Beovox 1000

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

chartz
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chartz replied on Sun, Nov 20 2016 5:41 PM

This said, I use my BM1000 and my BG1000/SP6 with S45-2 speakers with tremendous results.

Jacques

Jeppe
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Jeppe replied on Sun, Nov 20 2016 7:12 PM

Thanks for helping sorting out the transistor confusion. Rolf, that looks just like my plan.
And thanks for your advice for speakers!

This particular BM1000 is perhaps not in mint condition. But it deserves love nevertheless.
The radio scale looks different from what I see on other white key 1000's on the net. Perhaps it's a very late white key version? (it has no model no label)
I haven't figured out how to restore this part. Someone has taped the two parts of the scale, the thin front and the top section, together. There seems to have been some attachments at the corners, which now are broken off. Not sure how this was originally attached.

 

Dillen
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Dillen replied on Mon, Nov 21 2016 6:24 AM

It's an exportmodel.
Most units sold in Denmark had the names of danish radiostations printed on the dial, but they
wouldn't make much sense elsewhere so the exportmodels only had frequency and channelnumbers.

Your Beomaster is missing the top half of the front center rail. It's broken off - common problem as the plastic becomes brittle with age.

Beovox 1000 was recommended for Beomaster 1000, though it really deserved better - it's a capable and wonderful sounding amplifier.
Beovox 2702 will be fine. Even larger speakers would also be fine. Beovox 2400, 2600, 3000 etc.

Martin

Jeppe
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Jeppe replied on Mon, Nov 21 2016 4:53 PM

Thanks Martin,
Yes, I bought this in Sweden and I think it likely it was originally sold here.
I do hope so much I will be able to make it sound. I am very curious about it's sound. Not sure I can pull this off by myself, but I will try.

It looks like in this photo below (not mine, mine is even more broken). I have to fix this somehow. Thinking about it. Spares is probably not to think of. I have been thinking about visiting a hobby/model building store and see if they have something with which I can build up a frame for the transparent scale and have it attached.

I also wonder if anyone could advise about the zener diode ZF 9.1. I must purchase a new one. Swedish Elfa has two variations, 9.1V 3W or 9.1V 5W that I consider. There are also 1.3W versions. The service manual says "the electronic protection circuit will operate at a current drain of approx 4 W".. Is that what I should base this decision on? A simple calculation gave 3W, but I am not sure about this. The Wattage shouldn't affect the performance of the diode in any other way I believe?

rolfzetterberg
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Googling ZF 9,1 tells us it's a 500mW diode.Use a 1,3W.

I did a quick calculation of the current  through the zener diode and ended at about 8-9mA through the transistor and 10mA through the 1,8k resistor.

18mA in total,which gives a total power of about 170mW in the zener diode.

Jeppe
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Jeppe replied on Tue, Nov 22 2016 2:30 AM

Rolf, so grateful for your advice! My calculations were way off, as suspected.

Capacitors ordered from Mouser. Zener will be bought at Elfa.

Jeppe
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Jeppe replied on Wed, Nov 23 2016 10:37 PM

Today I bought a second BM1000. For reference..
Together with it came a pair of S45 speakers. They are in good condition cosmetically but the foam is bad and the need restoring. Do you want them? I give them away. I live in Stockholm Sweden. Space is getting scarce here. I hope they can come to a good home.

This BM1000 was supposed to work. But before plugging it in I took a look inside. Someone has been tampering with this one as well. The on/off and the mono keys have switched place. Some screws were missing. The fastening point on the top of the cabinet was broken. The schematics are missing. But worst was the horrible dirt. Thick dust. But not "nice" dust that you can blow away, but sticky, greasy dust. After some preliminary cleaning with a brush and compressed air, I just had to plug it in to see what happened. And it worked! Big Smile I have never heard a white keyed Beomaster 1000, but I had a feeling I would like the sound. And I do! Perhaps I have fallen in love.. Connecting it to a pair of Wharfedale Dentons (original early 70'ies or late 60'ies, newly restored) and a pair of Beovox 2702's (also newly restored) it really sings! I never made these speakers sing before like this. I even considered selling them because with my Tandberg equipment they just sound sad, dry, thin and hollow. How come this little receiver from 1969 can sound so "fat"? I love it!

Some people say this receiver is not for everyone, that it has a special sound. What do you think? For me, who is allergic to modern "analytical", sterile sound with treble like sharp glass that cuts my ears.. perhaps this is just what I was looking for. And this even without me having changed one component (in spite of it's age, it sounds like this.. What if components would age like a good wine, to mellow..).
I also have an unrestored black key BM1000 (not tested). I wonder how they differ in sound?

Leads me to the next question for you gentlemen and gentlewomen better versed in electronics than me. My plan is to keep this one as untouched as possible, while I restore the other one totally (every capacitor will be changed, at least all the electrolytics, I think I have 55 pcs waiting..). But is there anything I might want to do to avoid a disaster? I think, maybe I should change the two 2200uf 25V capacitors that I believe drives the amplifier? And perhaps the 2200 50V power cap? To avoid speaker blowup in a capacitor meltdown scenario? Now, I dare not use it for everyday enjoyment. But I don't want to tamper with it too much.

Oh, one more thing. Perhaps someone can advice, how to best clean away the oily greasy dust. See the photo. Isopropanyl alcohol, can it be used? Just bought some. Risk of destroying something, on the board for example? Perhaps you have better ideas. The greasy dust stuck on the transformer is specially bad and hard to remove.

Søren Mexico
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I have always cleaned mainly with IPA, (isopropyl alcohol) but I always take the unit down to the nearly last screw, even if I have to desolder, on hard to clean metal parts sometimes I use acetone (careful may strip paint and destroy plastic), rusty pieces I leave overnight with a thin oil layer and then clean off with acetone ( if not clean, use abrasive pads), then a thin coat of oil.

Some of the guy guys here recommend Windex (window cleaner) some of them mix it with IPA some use it directly and then clean with IPA afterwards.

I have a bottle of Windex here and will try it out on my next object.

I have never heard a white key BM 1000 but the sound should be special because of the germanium TRs

Good luck

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

Søren Mexico
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Even if the BM works, I would change all the electrolytic caps, here a pic from my BL 5000 of what happens when they start leaking

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Jeppe
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Jeppe replied on Thu, Nov 24 2016 1:32 AM

I wonder where does the grease go after applying IPA. I know the IPA evapourates, but the dirt..?

So IPA does not destroy the board or any other components and can be applied liberally I understand.
Cleaning it will be an interesting project too.

I hope to keep this one as original as possible, until I can compare the two.. But I understand they both need new capacitors. Thinking of that, if you change all the capacitors, isn't there a risk that the original sound is changed? (However on the other hand, all the capacitors are old and may not perform optimally, I know). What performance can we expect with modern day components? Has anyone noticed differences with different types/makes of the exactly same spec components? For the first BM1000 I bought all new capacitors, mostly Nichicon Fine Gold type.

Søren Mexico
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You wil have WASH to get the grease off, it will have to drain off with the IPA

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

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