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Beomaster 901 - Service and Repair

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Coldsmoke
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Coldsmoke Posted: Mon, Mar 18 2013 4:12 PM

Hello everyone,

I recently bought for a very fair price some old B&O equipements including a beocord 1900, a beomaster 5000 and a beomaster 901. The two first piece of equipement work quite fine although I am a little bit desapointed by the quality of the AFC... Anyway, it is set on my favorite radio station, so I feel happy enough.

The big issues come with the Beomaster 901: when I first checked the equipement I just plugged it to the electrical plug : the red light turned on, so I figured the equipement was working...

Having tried to connect the 901 to a pair of rl-60 I do own, I realised that the amplifier was'nt working (no sound at all in tuner nor aux mode...), I started so my first repairing project on an electronical equipement.... Having gave an eye to previous threads, I started with replacing the 100µF / 40V caps by 100µF/50V, and I'm still waiting for the other caps to be replaced ...

By the way, I'm lookinig for some parts like the two pieces of plexiglas in front of the tuner / volume sliders, rubber feet (non exhaustive..). Do you know where I can find these by a chance....?

I'd like just to warn you that I might need your help guys, these are a few years now that I left school (well I'm anyway a mechanical engineer not knowing much about electronics), so thanks iin advance, and talk to you soon :)

 

Florian

Peter
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Peter replied on Mon, Mar 18 2013 6:25 PM

Capacitors and variable resistors are a start though you will need measuring equipment to check everything is working. 

Trim parts are tricky - some members make their own parts - the perspex parts in particular.

Peter

Søren Mexico
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Check this thread it may give you some help or ideas of what you are into, that BM 901 was my first serious overhaul, as you I'm a mechanical engineer, and electronics a new world to me, since the 901, I started a long time relationship with a BM 4400.

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

Coldsmoke
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Coldsmoke replied on Tue, Mar 19 2013 3:18 PM

Hello gents,

Thanks for your quick answers, I decided to replace each cap on the circuit (but the ones made with aluminium foil) and I'll replace the variable resistors too.

Actually I couldn't find anywhere the specs for the variable resistors (type and setting), could you help me with that..?

By the way, my question might sound naïve to you but I am a little disturbed by those components that are like 2cm high, made of aluminium with a red / blue or white screwable device on top : any clue?

 

Tx in advance

 

Florian

tournedos
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tournedos replied on Tue, Mar 19 2013 4:50 PM

Coldsmoke:
By the way, my question might sound naïve to you but I am a little disturbed by those components that are like 2cm high, made of aluminium with a red / blue or white screwable device on top : any clue?

Coils in the tuner circuit. DO NOT touch the adjustments - the ferrite cores break very easily and you'll never get them back to where they should be without proper skills and test equipment.

--mika

Coldsmoke
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Coldsmoke replied on Wed, Mar 20 2013 7:28 PM

Thanks for the advice, I have to say that I tried to play with one of these but I figured that puting it back to the same position might be wise, I hope I didn't broke this little guy...

By the way I paid on an other website a few euros for a very bad quality scan of a part of the circuit.... I read when I registered here that paying for the silver or gold membership would allox me to access some service and repair manual... Is the 901 part of these manuals...? If it's the case, I think I'll aplly for membership then...

Søren Hammer
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Yes, the 901 service manual and diagrams are in the database - along with a good quality copy of the Beolab 5000 service manual.

Vinyl records, cassettes, open reel, valve amplifiers and film photography.

Coldsmoke
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Coldsmoke replied on Wed, Mar 20 2013 8:51 PM

Tx for the tip, I'll register right away :)

 

 

Coldsmoke
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Coldsmoke replied on Sun, Mar 24 2013 10:16 PM

Hi there,

Just a quick message to let you know that I finally achieved to fix the device : I replaced all caps and checked the setup of the different variable resistors.

To finish with the restauration, I might need your help to find the followings : I just need to find a new perspex (or to re-make it myself, but the round part's gonna be tough to make...), I also look for rubber feet, a rabbit-ear antenna and various fixing screws... I also consider replacing the linear potentiometers as the ones I use are a little noisy.

As this first project is soon finished I'm looking for a new one ... Any suggestion?

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