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Beomaster 1900 only stand-by light

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flipper62
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flipper62 posted on Tue, Dec 11 2018 12:49 AM

Dear members,

 

I recently received a Beomaster 1900 (type 1903), which powers up, but only the stand-by light is burning constantly. If I try a different button( like a preset FM), there is the sound of the relay for a fraction of a second, but nothing more. If I take a break and push a button again, the volume light blinks very short. I checked the relay and surrounding components, but couldn't find any perpetrator.

Does anyone have a clue?

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Dillen
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Answered (Verified) Dillen replied on Wed, Dec 12 2018 12:54 PM

A lamp kit is available, containing a full set of correct type and wattage of lamps.
It also has detailed dis/assembly instructions with photos and text.

Martin

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solderon29
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This unit has a fault sensor system,that automatically turns the unit off if a fault occurs,particularly in the main amplifier section.

Doe's your unit power up if the 'speakers are disconnected?

I suspect that you will need to investigate around the main amplifier.

Nick

Dillen
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Dillen replied on Tue, Dec 11 2018 2:36 PM

Check the speaker outputs for DC.
Check the solder joints for the output stage darlingtons.

Martin

flipper62
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Thank you both for your quick reply. Although the relay RL1 seemed to function corectly, it makes sparks.All the buttons are working now.The new situation: the stand-by button has to be pressed for a few seconds with a rattling sound of the relay, before it's turning off. I think the relay had too much sparks and the contacts are worn. I need a new relay, but where can I find it. B&O calls it relay 7600032. Ofcourse they didn't  manufacture it. Which relay should I buy?

Dillen
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Dillen replied on Wed, Dec 12 2018 7:01 AM

The relay will be fine.
The Beomaster will have a hard time going in to standby and it will act exactly as you describe, if the three tonecontrol lamps are wrong or burned.
They are used to bleed the 15V when going in to standby..
Check the lamps.

Martin

flipper62
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Hello Martin,

 

You're correct. Those lamps don't work. How do I remove the control panel. It seems to me this panel is glued with double sided  foam. Do I have to cut it away with a sharp metal ? or is there a hidden screw ?

jesperb
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jesperb replied on Wed, Dec 12 2018 12:16 PM

Screws are accessible from below, under the aluminium front 'nose'. Take a look from the bottom of the 1900 (might have to remove the bottom too) - see underside of bottom panel for screw locations for that operation.

Front panel is easy to get out, fiddly (not difficult) to get back in. Careful not to bend the flimsy metal strips/forks and avoid scratching the dark pvc, when you store it away.

When you have the touch panel off, the lamp PCB's are easily accessible, fastened with two screws each.
The lamp 'housings' clicks right out from the underside of the PCB's, making it much easier to swap the lamps.

Beogram TX, Beovox S45, Beovox MC 120.2, BeoSound 1, CX50, Beovox S75, Beomaster 2400

Dillen
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Answered (Verified) Dillen replied on Wed, Dec 12 2018 12:54 PM

A lamp kit is available, containing a full set of correct type and wattage of lamps.
It also has detailed dis/assembly instructions with photos and text.

Martin

flipper62
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Thank you for the instructions. I have found the bulbs. These are common car dashboard bulbs. 12v/80ma T3 type. I'll get me some tomorrow

Dillen
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Dillen replied on Wed, Dec 12 2018 8:41 PM

I don't know where you found those specs, but they are not correct. Even most servicemanuals give wrong specs (12V 1W I think is stated).
Look at the circuit for the tonecontrol lamps - they are fed close to 15V - this alone points to a lamp voltage spec higher than 12V, or they
wouldn't last long.

And they are not T3.
They are not socketed at all.
They have bare leads and are soldered directly into circuitboards, held by little metal clips.

Who gives out all this wrong info?

You can see the correct lamps here:
https://www.bonanza.com/listings/Lamp-kit-for-Bang-Olufsen-Beomaster-1900-1900-2-2300-2400-2400-2-bulbs-set-/522237003?st_id=81879970
Also available from the Beoparts website.

Anyway, the lamps in these Beomaster models forms part of the circuits they work in;

The lamps used for source selection forms part of the muting circuit (allowing for a brief muting at source switching),
the lamps behind the tonecontrol indicators are used for loading and bleeding the 15V supply,
the wattage of the two tuning discriminator lamps is critical for their own discriminating function,
and the volume control will often become irresponsive or start to run up or down by itself, if its lamps are wrong or burned.

The lamps are quite critical - and not at all common.
The lamps in the kits I make, are of a custom produced long-life type for the same reason. Sold without profit, before you ask, because
I had to accept a certain minimum amount - all just to get the lamps I needed for my own restorations and repairs.

Martin

flipper62
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Hello Martin,

 

I took them out, the bulb says 12v 80mA. I assumed this was correct, but maybe someone changed them before???

T3 can be bought without socket, only leads.

Dillen
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Dillen replied on Wed, Dec 12 2018 9:02 PM

flipper62:

Hello Martin,

 

I took them out, the bulb says 12v 30mA. I assumed this was correct, but maybe someone changed them before???

It certainly suggests that.

Martin

flipper62
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Hello Martin,

I discovered another mistake in the manual. Part 8 of the components list of my service manual mentions C1 as 47 uf, as the schematic says 470uf. I looked at it and it shows 470uf on the capacitor. Same mistake with the resistor before the the tone/balance indicators (part 8) schematic says 68 ohm, parts list mentions 680ohm. The board shows 3x resistors each 68 ohms (blue-gray-black-silver)

 

Are there incorrect manuals in circulation?

 

Dillen
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Dillen replied on Thu, Dec 13 2018 7:46 AM

flipper62:

Are there incorrect manuals in circulation?

There are no correct manuals in circulation.
There are different manual issues, but they all have countless typos and other mistakes.
Tech note updates etc. occasionally had some corrections to glue in, but some of them had mistakes too.
Best is usually to trust what's fitted from factory.

Martin

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