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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

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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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chartz
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I only have the black version so no!

Funny you should mention you want to fix a black one, I for one would like to find a white one - possibly white, not yellow... 

Now what about that Beogram eh?

 

 

 

Jacques

Jeppe
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Jeppe replied on Fri, Jan 6 2017 3:57 PM

Yes, looking for a nice Beogram!
Was not in a hurry for the plan was to restore the Beomaster first, but now it's time to find a Beogram too. You recommend the Beogram 1000?

I have never owned a gramophone and know very little about it's mechanics. Where do you find spares, like needles and spares for example for the "drive train"?

I saw that there were a couple of white key Beomasters on sale on French ebay lately. You are located in France I believe. I also saw a couple on hifishark.com advertised in France. If you find one and start to restore it, I would love to follow your restoration.

Jeppe
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Jeppe replied on Sun, Jan 8 2017 3:52 PM

I have a question that I find very interesting and would be happy if someone could bring light into this matter.

In another thread I found this quote by Martin:
Now is not the time for me to tell you that the large filter capacitor can explode. Don't ask me how I know
or how far I wasn't from the Beomaster...
I like to replace it with a 2200uF 50V component in all Beomasters of this type. The rectifier is properly dimensioned
and will have no problem at all with the somewhat higher rush-in current plus it will give a slightly better filtering (and a
greatly reduced risk of explosion).
The two output series capacitors can also be replaced with capacitors of the same type. The originals will have passed
their sell-by-date by now and it will give a much needed kick to the damping factor which in turn means a much
better control over the low frequency (bass) range. You will like this, I know.

In fact I did just this, replaced this big cap with a 2200uF 50V. I also replaced the two output series capacitors, with 2200uF 25V (Nichicon KA Audio Series). These are slightly over spec. I know the +/-20% rule. But how far off can we go in F value. I could not find close enough values for some components. Are there some places in the circuit where we must be more careful to be close to original compared to others? For example, in the schematics is the capacitor 905, it's a 125uF 16V, close to the zener diode and the AC128 I replaced. For this I didn't have a close value, I used a 220uF 16V (Nichicon FG Audio Series). Aware that this was 76% higher I tried it anyway. Now I don't know for sure what this capacitor does, but it seems to be involved in power supply. Soon I plan to replace several caps in the amp section - some are originally 1,6uF while I plan to use 2,2, and there are many more 125uF caps in this section, but dare I replace them with 220? What would you do?
I know you could put them in parallell and so, but now the question is about overspec value on a single cap. I also want to stay within the same range, that is Nichicon audio series and Elna Silmic, so that limits my choices somewhat.
It works fine now though, with what I have replaced so far.Thumbs Up

Another question, do I need to upload photos to Media library to be able to attach them here?

Thanks so far for all the help you have given! I enjoy this forum tremendously.

Dillen
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It's next to impossible to give a secure handrule for replacing no-longer-available component values, besides the
+/- 20% "rule". Upping the capacitance of caps in certain positions will give a problem rather than an "upgrade".
However, for most electrolytic capacitors, it'll be alright to grab the next higher capacitance value.
Well, as long as we talk about filtering and decoupling capacitors, anyways.

From 125uF to 220uF is quite an amount. I would recommend 150uF instead (which is not a standard value, but
commonly available regardless).

The output series capacitors can be upgraded a little more freely than other caps, it will give a better
damping factor, which you may (or may not) hear as a slightly tighter bass response. - But the original
values were perfectly adequate already.

In most cases:
1,6uF -> 2,2uF
80uF -> 100uF
etc.
Will be perferctly acceptable.

Martin

Jeppe
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Jeppe replied on Sun, Jan 8 2017 4:46 PM

Thank you Martin.

I see. I will really try not to stray too far away from the original values.
Perhaps I could get away with the 220uF instead of 125uF this time because it is a filtering or decoupling capacitor (I am not quite sure what). But for the amplifier section I was sceptic, so I have ordered 150uF Vishay/Sprague capacitors. One could perhaps use a 100uF and a 33uF  together, but that seems messy.

There was also one case where I could not find a 50uF 40V capacitor so I ordered a 47uF 50V, but that I assumed was close enough even if I avoid lower values.

I have no intention to try to "upgrade" the design, actually I really want to avoid it, my ambition is to restore it as close to original as possible with high quality components.

Jeppe
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Jeppe replied on Mon, Jan 9 2017 3:37 PM

The work continues. Today 25 capacitors were replaced. I think that was all electrolytics in the amplifier section, except those 125uF mentioned earlier.

It still works. Being a complete amateur I am glad I could do this.

The sound is different from yesterday, but maybe because the caps are new and need a few hours. There is more clarity at high frequencies but the lower end is still the same. Odd thing is that at low volume there is a bit less treble than at higher volumes, when increasing volume treble also increases slightly. I hope this is not an issue because some of my caps were out of spec..

There is a "brrrr" sound from the transformer (sometimes disappears for a little while).

I used IPA to clean switches. Then something called PRF 7-78, its a contact spray I was recommended at the Swedish store Kjell&Co, for using with electronics. It is supposed to clean and leave a protective "oil film". Is this really good? It leaves a greasy film where sprayed. After using it on the switches, particularly the Radio source switch - I ended up with no reception at all. Then switching a few times and it came back. Just wonder if this spray is really good or if you sensible guys use only IPA?Unsure

ConfusedOh yes, I have another question for you who still follow my project, how come my other Beomaster 1000 have excellent FM reception even without antenna, while this one has very weak reception (almost nothing is heard)? I read somewhere that Beomaster 1000 has a built in antenna, but that must surely have been an error?




Jeppe
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Jeppe replied on Mon, Jan 9 2017 5:56 PM

It died! Crying

There was a mystery component, a capacitor that did not exist in schematics, at least I think so. A 125uF/16V capacitor. After exchanging this it just makes a "wowowowowo" sound.. I don't think its because of this component, I changed it back to the old one - to no use.

I have done all I can, very sad that it worked earlier and sounded great and now it doesn't work at all..

I didn't use the power switch, just plugged the cable in and out (keys not connected and didn't want to stick things down in there), perhaps this caused some power surge that destroyed a transistor or something..?Hmm Nothing should have been shorted, no things left could have caused damage.. I have no idea what happened.
I am very sad..

See photo for mystery component if you are interested.

Christian Christensen
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Come over to me with it.
I have about 2-3 weeks line right now, but will have a look at it when I can

Christian 

My re-capped M75 are my precious diamonds.

Jeppe
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Jeppe replied on Mon, Jan 9 2017 6:50 PM

Smile My saviour!
Tack.

I really wonder what happened today..

Dillen
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Beomaster 1000 has no built-in antennas.
You didn't use low-ESR capacitors - did you?
That could explain both the change in sound and eventual motorboating.

Martin

Jeppe
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Jeppe replied on Mon, Jan 9 2017 10:21 PM

No built in antenna, I thought so. Quite sure I read it somewhere but of course investigating the matter in my own machines made me conclude there was no such thing.

No I didn't use low ESR capacitors. They were all Nichicon audio grade, KA or FG series. These are not specially low ESR I believe, and should fit these applications.
The change in sound is quite subtle, not so obvious. I don't think it is necessarily for the worse, except perhaps that treble/bass ratio changes a little bit depending on volume.

The motorboating sound was a change for worse for sure, in fact it's completely unusable now, it's not subtle - it's possibly speaker damaging bad. Maybe something with the transformer, it did make a sound like a bumblebee before.

Dillen
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Dillen replied on Tue, Jan 10 2017 6:37 AM

Check that you got the polarity correct for all caps.

" treble/bass ratio changes a little bit depending on volume"  I suppose is the built-in Loudness you can hear.

Martin

Jeppe
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Jeppe replied on Tue, Jan 10 2017 7:34 AM

Yes, I should have got the polarities right, I am quite sure. Also it worked and played beautifully for a while.

I had done all work for the day and sat down with a cup of tea, very satisfied with myself. Coffee Then I started to think about that "mystery capacitor", and realized I probably had made a mistake. This was while the Beomaster was playing (some bossa nova I think). This capacitor was not marked correctly in the schematics, and I had misunderstood it and put in a much higher F and V capacitor. Though it played so beautifully I decided to replace it with a more suitable cap, because perhaps this was the reason the radio was odd and the mystery cap seems to be involved with the radiosection. I put a more suitable cap in there instead, and then tested it - all that came out was "wowowowoo". I put back the original cap (125uF 16V), not really thinking it would make a change - which it didn't - still "wowowoo". This little operation couldn't possibly have cause the problem I think..

That was a long story - in short - it worked perfectly and then it stopped working for a reason I can't understand.

The built in Loudness, it's a step towards putting it back in original shape that I could hear this more clearly suddenly then.
Does all Beomaster 1000's have built in Loudness?

Christian Christensen
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The built in loudness has a perfect match with Beovox 1000 in sensititvity and and caracter.
I would never modify  a beomaster in such way

My re-capped M75 are my precious diamonds.

Dillen
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Dillen replied on Wed, Jan 11 2017 6:15 AM

Jeppe:

Does all Beomaster 1000's have built in Loudness?

Yes.

Martin

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