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Beomaster 8000 Project

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sonavor
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sonavor posted on Tue, Aug 6 2013 8:28 AM

Here is the Beomaster 8000 that I acquired as part of an 8000 system earlier this year. I have been wanting to get this receiver working again but kept getting side-tracked. I think it is now time to dive into it. I have the service manual so I think I am set.

 

 


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Leslie
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Leslie replied on Sun, Sep 15 2013 5:21 AM

One word John, SUPERB!

 

Brengen & Ophalen

Menahem Yachad
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Great Job!

Sometimes one has a project which is the biggest learning experience of all. I think this was yours.

Menahem

BO
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BO replied on Sun, Sep 15 2013 11:03 AM

Impressive! Congrats!

//Bo.
A long list...

tamtapir
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tamtapir replied on Sun, Sep 15 2013 12:12 PM

Love it!

/***

Dennis
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Dennis replied on Thu, Sep 19 2013 10:57 PM

What a fantastic job you did! I just bought one myself and can't wait to work on it. Maybe I will look into replacing some of the wiring system reading how delicate it is?

- Dennis Smile

sonavor
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sonavor replied on Mon, Sep 23 2013 11:28 PM

Dennis:

What a fantastic job you did! I just bought one myself and can't wait to work on it. Maybe I will look into replacing some of the wiring system reading how delicate it is?

- Dennis Smile

Congratulations.  I also picked up another one to refurbish in the future.  I want to go back and work on the FM boards I swapped out of my completed unit so this latest one will provide a test bed for that. Looking back at this completed receiver, I'm not sure I would re-do the wiring. The connections are touchy but I got to where mine always work. Changing the wiring would mean changing connectors. It could be done but I think it would be a painstaking job.  I think it is easier to just be aware and be careful with the existing wiring. I also put a little contact cleaner on all the connections when I went through mine.  The end result is very rewarding.  I really like this receiver now.

-sonavor

sonavor
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This weekend my Beomaster 8000 started losing sound from the Left Channel.  I was worried there was an output amplifier problem but troubleshooting has shown that the signal is being lost coming out of the preamp board (03) going to the tone control board (04). 

With the Beomaster opened back up, I am able to play music through it for a couple hours straight and not encounter any problem. Close it back up, the problem returns. Figuring it could be a solder joint on the preamp board, I pulled the board and reflowed the solder joints of the connectors. That didn't fix the problem. I also reflowed the P27 connector on the tone control board as that is the destination of the stereo output from the preamp board.  Same result.

When the problem shows up, I have not been able to get it to go away by moving any of the cables.  I am able to get the problem to clear by connecting my scope probe to the Left Channel output of the preamp (at P16-1). So I could have a cold solder joint around that node. I will resolder R158, TR103, TR104 and C136.

Here is the schematic of the area involved .  Only the right channel details are shown on the schematic but the Left Channel components are the same as the right except the designators are in the 100 range instead of 200.


sonavor
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Here is a picture of preamp board with my scope probe on the R158 node that goes to P16-1 (Left Channel output to Tone Control board).


Dillen
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In cases like this with channel dropouts I like to play around a bit with the volume setting trimmers at the left side
of the Beomaster.
They are rarely used so will often oxidize and cause intermittent problems.

Martin

sonavor
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I pulled the 03 module (preamp board) and reflowed the solder joints on the left channel output circuit components. I couldn't remember if I cleaned the input level trimmers for the inputs when I originally restored this receiver so I cleaned them as well while I had the board out.

It looks like the Beomaster is back to 100% again.  I have played it for a couple of hours tonight and the left channel hasn't dropped out once.

 


sonavor
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Here is the component side of the 03 board


sonavor
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Here is the area I believed to be the problem area - TR104, R158, TR103, C136


sonavor
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The reflowed solder joints


sonavor
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The 03 module reinstalled


Menahem Yachad
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When doing a restoration, there are 2 components which I replace, without taking into account whether they are good or not.

1. All the electrolytics - as is commonly done and well-known here.

2. All the trimmer potentiometers. The original open, exposed trimmers are subject to dust and smoke contamination, which causes the oxidation. The original carbon-based units have a power handling capability of 0.1W. New 10mm drop-in replacements (either Piher PTC10 or Bourns 3352) are sealed, have a Ceramic element, and a power capacity of 0.5W. They cost approx $1 each at major distributors, so it is a no-brainer to replace, without even thinking about it. It saves so much hassle afterwards.......

Menahem

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