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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 Thu, Nov 24 2016 6:50 AM

The two 2200uF capacitors on the main board don't "drive" the amplifiers, they are the output series capacitors.
The 2200uF filter capacitor in front of the transformer is a nasty one, it is known to go with a terrific bang, leaving a huge mess.
I would replace the three.

Note the polarity of the filter capacitor - remember this Beomaster has positive ground.

Martin

Jeppe
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Jeppe replied on Fri, Nov 25 2016 5:08 AM

The three largest capacitors has been changed. The inside cleaned.
It works! The sound is still nice, in spite of my molestation.
It was difficult. Specially soldering those points where legs of the caps and several cables go together was difficult.
I'll leave the restoration from now to pro's. Too much for an amateur like me.Confused If you saw my solder joints you may ban me from this forum.
It was fun though, studying and preparing.

Someone who could restore them for me?!

I now have three machines, two white keyed and one black. And I have sets of components for restoring two.
I have become a complete fan of the white keyed Beomaster..
They white ones all have their own individual cosmetical problems. I would love to have one in mint condition, or nearly mint.
What do you do when the scale front rail has broken off, like in my earlier photo? I don't want to scrap it as a spares machine, I would hate that, and it is in nice condition except from this. Was thinking of building a new front, but I am not really good at such things.

Jeppe
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Jeppe replied on Fri, Nov 25 2016 10:13 AM

Again, I must say how impressed I am with the sound of this little receiver!
I have had several vintage, mostly 70ies, receivers and setups with different speakers. I believe I was looking for a special sound, I think this is it, perhaps you can call it warmth.

It has been playing some challenging music today, that my other setups couldn't do justice to. Indie-pop for example, heavily guitarbased indie-pop never sounded this good. Those dreamy shoegaze guitars can make your ears bleed on the wrong stereo but sound heavenly on the right. But it can also play house and techno, there is enough deep end. And it is lovely with jazz too, just played Diana Krall. And with 80'ies music, now I could really enjoy ABC's 80-hits. It goes well with any kind of music.

Bought a used Sony Discman and going thru my cd collection, which I haven't heard for years. So much fun.

The Beomaster 1000 survived my restoration attempt. It plays beautifully.
This is my favourite amplifier ever.

chartz
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chartz replied on Fri, Nov 25 2016 12:48 PM
Wait till you hook up a Beogram 1000 to it!

You will then understand what is good vintage sound.

Then you will want another Beomaster...

You don't know it yet but you've just caught the Beovirus I think.

We do have a doctor here, however, before you rush off to A&E Stick out tongue

Jacques

Jeppe
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Jeppe replied on Fri, Nov 25 2016 4:58 PM

Jacques, I have the virus, definitely..
It's good to have this forum to have the support of fellow infectees.
There are so many of these machines for sale on ebay and local ads, and they cost so little. But I already have three, why do I keep looking in these ads and wanting to buy another one..?

You know, the design has grown tremendously on me too. First I thought it older looking than the 70'ies receivers I had, and I thought the 1001 and 1200 really cool looking. But now I really appreciate the 1000's aesthetics. It is more than a receiver, almost like a piece of litte furniture.

And then, as you recommend I have to get myself a beogram 1000 too.
Now I use the newly bought Discman and a Nuforce DAC.


Oh, I have a question for you, if anyone can answer?
The Beomaster 1000 has three inputs. One is Tape, which I normally use for line out from my source (computer/DAC).
But now I have two sources, and to avoid having to switch cables, I want to use one of the other inputs on the receiver, there are Gram1 and Gram2. In the specs it says:
Gramophone input 1: GV 42 VF Stereo record player or crystal pick-up: sensitivity 15mV/50mW.
Gramophone input 2: G 42 V Stereo record player (less pre-amplifier). Sensitivity 200 uV/47KOhm at 50 mV.

I tried briefly the gram inputs from the CD line out to the gramophone inputs, Gram1 sounds fine, Gram2 sounds like overload.
Is it ok to use the Gram1 for a line out from my a DAC or CD? As I understand it is still for a weaker signal than Tape, but it sounds ok..

Thanks for all your help!

Søren Mexico
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Gram 1 is OK, and here just to feed your BeoVirus

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

chartz
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chartz replied on Fri, Nov 25 2016 7:12 PM

The QI input is indeed made to accept ceramic cartridges, once found on lesser turntables. The same type found on Dansettes if you prefer. It isn't really suited to anything else.And not quite hi-fi!

Even the Tape input will be saturated by the 2V of CD players and DACs. You need an attenuator, unless your sources have a volume control.

The Beomaster will give its very best with an SP6 (Beogram connected to QII) and through its very own radio section.

Jacques

Jeppe
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Jeppe replied on Fri, Nov 25 2016 11:02 PM

Thanks Sören and Jacques!

After all, there are worse addictions.. This is not bad for health at all. Not even that detrimental to the wallet.

The inputs, hmm.. No level control on the CD but the DAC has. It sounds really good from the Discman though, even though possibly too much fed into the poor thing.

So you are saying that the Q1 and Q2 shouldn't be used at all (except for gramophones) for quality sound?

An attenuator! Shouldn't be too difficult to cook one up myself. Anyone has a recipe?

By the way, I was surprised at the radio section. Not that I listen much to radio, Swedish radio is quite horrible, except P1 the state channel that plays some jazz and classic. My other vintage receivers, like Tandberg, usually need an antenna. I didn't even expect the radio section work on this BM1000, but it works super and stations are loud and clear, better than any of my other receivers, although I didn't even connect an antenna.

Jeppe
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Jeppe replied on Sat, Nov 26 2016 2:53 PM

Too high line level is perhaps a bigger problem than I thought.
I have experienced these problems:

Most line level components (CD, Tape, Tuner etc) have rather too much gain (particularly CD) which results in an amplifiers full volume point being reached around halfway on the volume control. This gives the impression of lots of power but can make it all too easy to damage speakers. More importantly though volume controls are actually quite inaccurate and degrade the sound more when they are at lower levels.
(from Rothwell Audio Products)

Perhaps this is the solution:
http://www.rothwellaudioproducts.co.uk/html/attenuators.html

Review here:
http://www.enjoythemusic.com/magazine/equipment/0803/rothwell.htm



tournedos
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Jeppe:
Perhaps this is the solution:
http://www.rothwellaudioproducts.co.uk/html/attenuators.html


I'm sure they'll do the job and are an easy and neat solution if you have an RCA equipped source anyway, but oh my, the hi-fi talk and the prices...

As I'm ignorant Big Smile, I would be right with the unknown forum guy: "a premade Shiny Gizmo to replace a silly simple Resistor placed inna Interconnect??"

...and add a silly simple resistor. Gramophone 1 and Tape inputs of Beomaster 1000 seem to be specified as 500 kOhms, 200 mV. That's low level and high impedance in modern terms. If your CD or DAC outputs 2Vp-p, you will need to attenuate the voltage 1:10 (equalling -20 dB) to avoid overloading the inputs.

So I would actually use two silly simple resistors (per channel). Out of my hat came these suggested values. Far from critical, adjust to whatever resistors you have lying around as long as the ratio stays roughly the same and the total resistance between 5 k and 50 k or something.


--mika

Jeppe
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Jeppe replied on Mon, Nov 28 2016 5:41 PM

Thanks Mika!
I thought that one should be able to use some silly little resistors to build one's own attenuator.
40 pounds for the Rothwell gizmo isn't excatly cheap, but on the other hand it's probably well made, which my own gizmo probably will not be.

When I measured the voltages by the way, it was a mess. Not until I used a high quality multimeter did I see that perhaps the values of the CD wasn't that high, but rather around 0,4V, or up to 0,4V. With the DAC I could adjust the output so that it stays below 0,2V.

What is the normal output supposed to be in the line out of a CD?
Does impedance play a part in this?

Jeppe
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Jeppe replied on Mon, Nov 28 2016 5:46 PM

Now something different, which fellow Beomaster 1000 fans may find interesting.
An article from the Swedish magazine Populär Mekanik, from 5th of May 1965. A short review.

My translation to English below.

For the music lover:
Beomaster 1000


Wonderful news for music lovers - a compact fully transistorized combination of HiFi-stereoamplifier and FM-radio with many uses.

The highly selective FM-radio sectio: enlarged FM-band (up to 108 Mc/c). 3-time(?) variable capacitor and 4-stage middle frequency amplifier with 4 limiters. Automatically sucks in FM-stations and locks them at the best setting. Built in FM-antenna.
---
Special indicator for station setting. Prepared for coming radio-stereophonic broadcasts over one station, designed so that a B&O multiplex-unit (sterodecoder) can be connected to a multipole built in connector.
Equipped with a "Beacon" indicator lamp, which lights up when the reciever is tuned to a station that broadcasts FM-stereo. This indicator lamp also lights up when set for playing stereorecords or stereotapes.
---
Constructed in accordance with the international I.E.C.-standard for oscillatorradiation, so that by using Beomaster 1000 one does not risk disturbing the neighbour's radio- or TV-reception.

The amplifier section, over which both stereophonic and normal records can be played, has a very powerful output power of not less than 2x15 watts. The speaker switch can direct 2 pairs of stereophonic speakersystems, for example a pair in the living room and another or several set of speakers in other rooms.
Separate, powerful bass- and treblecontrols. Balancecontrol for correct "stereophonic sounddistribution" when playing stereorecords or tape.
Physiologically compensated volumecontrol, which gives full balance in the whole tonal area at all levels. Very low distortion, thanks to the transistorized, transformerless amplifier.
Separate treble- and rumblefilters. Pushbuttonswitches for the following connections: FM-radio, FM-automatic, taperecorder, and gramophone 1 and gramophone 2. Low power consumption.
---
Beomaster 1000 is constructed for connection of external speakers, for example the groundbreaking B&O pressurechamberspeakers.

Jeppe
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Jeppe replied on Thu, Jan 5 2017 9:22 AM

Not sure if someone still follows this thread, but here is an update on my Beomaster 1000. It took a while, but capacitors, zener diodes and a few new old stock AC128 transistors (found on ebay) was bought. Yesterday I exchanged 11 capacitors, one zener diode and the AC128-3, which had been replaced by someone with a silicon transistor that was fried. I also made my own heat sink for the transistor, which you can see as a little copper "star". Not sure if that was really necessary, if those transistors get that hot, but it originally was mounted in a sort of heat sink, that now seems disfunctional, so I thought I should make some sort of heat sink, it was a fun project. The Beomaster now works and plays beautifully! It's connected to a pair of Beovox 2702 and a pair of Wharfedale Denton from about 1970. Superb sound! This machine is a jewel.

I am amazed that the capacitors still seem to be working and have retained their values. They are like 50 years old. I was going to replace ALL capacitors just for the hell of it, to have it back to factory new condition, but now I hesitate, is it necessary? It sounds great as it is.

tournedos
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Sure we follow! Nice work and glad you like it. I had mine (the later black version) for a long time before actually trying it out properly, and was surprised at how good it was.

All the electrolytic caps might be better replaced, but if it works & sounds good now and you don't mind opening it again if need arises, I would probably just button up the receiver and enjoy it.

Plastic film/foil caps and ceramic caps don't usually age at all, so there is no need to replace them unless they are physically cracked.

--mika

Jeppe
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Jeppe replied on Thu, Jan 5 2017 5:17 PM

Thanks Mika!

There are some caps in the schematics labeled PE, and some other like ceramic, these usually have lower values and high voltages. I have had some problems locating replacements for these and also heard that they don't age like electrolytics. But there are quite a few electrolytics that should be totally aged now, or so I thought, but I haven't found one that was severely bad, after 50 years. But I still wonder if perhaps their performance has deteroriated somewhat, although the F values are still within spec (this is the only value I can measure), and what would be gained from replacing them..?
I may just button it up and enjoy it!

I paid 190 kronor for this Beomaster, that is like 20 euro, then another 20 euro for components. That is absolutely amazing for this sound quality, I love it!

The front rail of the radio scale is still broken and I am looking for a way to solve this, maybe construct something. If anyone has a clue of how to solve this I am eager to hear!

Next project is to wake up a black version Beomaster that is waiting in my storage room. Would be so interesting to compare them. Have anyone compared the black and white version in sound impression?

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