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Beomaster 1900 quiet muffled left channel

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nataniel
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nataniel posted on Wed, May 28 2014 9:56 PM

Hi folks,

I'm working through fixing up a Beomaster 1900 I bought a few weeks ago for a bargain.

The left channel is sounding muffled or hollow in the midrange.  I have tested this for Tape in (playing an Ipod) and for FM, and for speakers A, B and headphones out.  And I'm about 90% sure it actually had this problem before I started fiddling with it.

I bought the lights/ capacitors/ rectifier from Dillen on this forum, and replaced all of them, successfully I think.  I replaced them because the volume control was stuck on full, and several of the lights were out.  Replacing the volume control lights alone actually fixed this problem, but I went ahead and replaced the capacitors as well.

Incidentally the 'Loudness' button gives of a lot of crackle when its switched, I'll have a look at the wiring behind it shortly.

Any ideas???

Cheers, Nataniel.

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nataniel
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nataniel replied on Thu, May 29 2014 10:15 PM

Does anyone have a suggestion for what might be causing the muffled left channel?  And how to fix it?

Cheers.

Dillen
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Dillen replied on Fri, May 30 2014 6:44 AM

A defective tonecontrol slider, - perhaps the treble ?

Martin

TrueBlue
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maybe you can sell him one of them too ay?....pfft

TrueBlue
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frrrt

TrueBlue
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sounds more likely to be a poor signal connection due to a faulty balance slider....and if it isn't broken already, I think it would be a good idea to de solder the balance potentiometer (slider) and put a drop of glue on the plastic clip that holds the two plates on to reinforce it....as this part will inevitably break......

here is a link

https://www.flickr.com/photos/bartdubelaar/609280931/

its a fiddly job....but will cost you no more than time and some super glue...don't use to much either

 

Dillen
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Dillen replied on Fri, May 30 2014 1:32 PM

TrueBlue:

maybe you can sell him one of them too ay?....pfft

I don't need to sell anything but occasionally someone needs to buy something.
Advice is always free.

To place sales/wanted ads a minimum of silver membership is asked for.

What was that in your other post ?

Martin

nataniel
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OK, here's an update....

I have pulled apart the three sliders/pots and cleaned them.  All contacts were in place and intact.  The problem is still there.  Just to clarify - I do get a response out of all the sliders, on both channels. 

The same problem is there - my right channel sounds great, left channel sounds flat, hollow, muffled.  Is there any way to further diagnose what could be wrong?  

Any ideas please?? I really want to get this think working properly!

Traverso
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Dear True Blue

I believe you should calm down with this kind of overstated comment.

Regarding B&O products Mr Martin DILLEN is the technical reference and is always available for guiding.

In addition the 1900/2400 is the one he knows a lot. 

Enjoy your B&O experience

 

Alain

 

Traverso
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Dear True Blue, 

I believe you should calm down with this kind of overstated comment.

Regarding B&O products Mr Martin DILLEN is the technical reference and is always available for guiding.

In addition the 1900/2400 is the one he knows a lot. 

Enjoy your B&O experience

 

Alain

 

Søren Mexico
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As you changed the caps in both channels, check polarity on all changed caps in the left channel, and check and adjust voltages according to manual.

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

Dillen
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Dillen replied on Thu, Jun 12 2014 6:32 PM

What Søren says. Particularly the idle currents. A very bad setting of idle current can cause an awful sound.

Then isolate the problem circuit by cross-connecting left/right channels;
Lift one pin of C200 and C300 respectively and cross-connect to feed the left channel signal source to the
right channel tonecontrol and amplifier and vice versa.
See if the muffled sound is still coming out the same speaker.
Note the results, put everything back and then do the same with the amp inputs C219 / C319.
This will fairly easily give you (and us) an idea where to look further.
Let us know what you find.

Martin

TrueBlue
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Start with a basic diode test on all transistors....

Leslie
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Leslie replied on Sat, Jun 14 2014 5:55 AM

Traverso:

Dear True Blue

I believe you should calm down with this kind of overstated comment.

Regarding B&O products Mr Martin DILLEN is the technical reference and is always available for guiding.

In addition the 1900/2400 is the one he knows a lot. 

Enjoy your B&O experience

 

Alain

 

As many others..

 

Brengen & Ophalen

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