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Volume indicator lamps

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Aad Jansse
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Aad Jansse posted on Wed, Mar 4 2020 9:27 PM

An other/another request for help this time. 

I got a Beomaster 2400 this week, good sound, but a few incandescent lamps were broken and by now replaced. Tuning is OK, volume control up and down soundwise also OK, but even after mounting new bulps, they are not shining.

Do I have to look for a culprit in the schematic section as depicted in this picture?.

As usual I am looking forward to any suggestion..

Aad


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Aad Jansse
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I am sure those are the correct lamps: they come from a srapped obsolete BM1900 and had virgin solderings.

There must be in my scrap parts somewhere those TR's and the D (BC549C, BC558B and D4148).I will test them later,
I'll be away for a couple of days.

Thanks so far,

Aad

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Dillen
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Is the 15V supply present across the two lamps?

Martin

Aad Jansse
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As soon as I am home I will check the 15V

just to picture a clear situation: I “borrowed” the lamps from a donor BM1900.

Aad Jansse
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Meanwhile an electronically experienced friend of mine was trying to find the cause of a problem in one of my BM2400 twinbrother/sisters, a BM 1900.The latter , subject to a minor cosmetical operation all of a sudden, while I was lifting it grabbing by a heatsink, that appeared to be a little loose, changed playing music for a fat humming. I immediately switched it off and did not touch it until handling over it to my friend later. Upon switching it on he informed me that there was a very loud  familiar sound: music that was, but through one channel, which was not to be silenced , nor did the volume control react on  trying to balance the output properly. What could now be the problem? ( I will still remain a B& O addict, nevertheless)

I hope that this post is not rejected as a non direct relevant  BM 2400 issue.

Aad Jansse
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I checked 2 spots: the picture shows where i found two voltages;

 whereas the diagram requires 7.9 V, I find in my case 2.25 V and one lamp shining, eaqual intensity at  all volume levels. 

Where goes it wromg?


Aad Jansse
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Rotterdam (Neth)
227 Posts
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I checked 2 spots: the picture shows where i found two voltages;

 whereas the diagram requires 7.9 V, I find in my case 2.25 V and one lamp shining, eaqual intensity at  all volume levels. 

Where goes it wrong?

Aad Jansse
Top 500 Contributor
Rotterdam (Neth)
227 Posts
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Silver Member

I checked 2 spots: the picture shows where i found two voltages;

 whereas the diagram requires 7.9 V, I find in my case 2.25 V and one lamp shining, eaqual intensity at  all volume levels. 

Where goes it wrong?

Dillen
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Dillen replied on Tue, Mar 10 2020 1:52 PM

Again: Is the 15V supply present across the two lamps?

Martin

Aad Jansse
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I need some explanation  : do the pictures help to presize what you ask?


Aad Jansse
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"Real world""


Dillen
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Dillen replied on Wed, Mar 11 2020 12:31 PM

If you are absolutely sure that the lamps are correct specs (don't trust the servicemanuals, most of them have a typo),
I suggest you replace TR12, TR13 and D13.

Martin

Aad Jansse
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Verified by Aad Jansse

I am sure those are the correct lamps: they come from a srapped obsolete BM1900 and had virgin solderings.

There must be in my scrap parts somewhere those TR's and the D (BC549C, BC558B and D4148).I will test them later,
I'll be away for a couple of days.

Thanks so far,

Aad

Aad Jansse
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Rotterdam (Neth)
227 Posts
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The lamps have proven to be the correct ones: the 2 TR’s appeared to refuse their tasks: both were faulty:

After having replaced them by good ones the BM2400 is doing well, I thought, because in the process of getting the volume indicator working properly I did not notice that there was only one channel producing sound, caused by the balance slider. It appeared that one of the tiny basterds inside had come off his plastic fitting which one was not damaged: replacing this small part brought back 2-channel sound.

So all is  well that ends well, thanks to your help, although there are more patients waiting.

(Where corona virus should be feared I still do not take any drugs against the B&O virus)

Aad

 

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