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Beogram 4000 Type 5215 - dial lights issue [solved]

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Velvet
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Velvet posted on Mon, Dec 3 2018 8:16 AM

Hello,

 first post here in this wonderful forum. I started recapping and fine-tuning my BG4000. This beauty came from UK (I live in Italy) around 2005 in terrible conditions because of a bad packaging. Luckily nothing was broken but many parts were disassembled including the arm mechanism. I was able to put everything in place and let it work for many years since then.

But at a certain point it began to develop strange issues: self power-on, 7" not recognized and other little gremlins. Ok, time for a total recap and a tuning following service manual.

Recapping was done with Vishay, Panasonic and Nichicon electrolytics. One of the main unipolar caps was shorted and others were out of specs. Tantalum were OK but I replaced with electrolitycs. Now the motor spins fine and quiet, sine-wave is clean both at 33 and 45 rpm at 6,2Volts (@33), no more self-power on.

 

But I have a new issue: the two dial scale lights self-power on when I plug the beogram to mains. They're always on, even if I press OFF . Other functions are correct (strobe light, motor, arm transport power On and OFF). 

Any suggestions or ideas will be much appreciated..

 


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Craig
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Craig replied on Wed, Dec 12 2018 5:55 AM

Good job......I'm also going through the detection arm issue so will keep abreast of each other. I do have a set of B&O training notes which provide a good amount of detail on these circuits (donated by solderon)….I have forwarded these to the site for inclusion in the service manual area in the fullness of time, however if you would like a copy now email me.

Craig

Velvet
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Velvet replied on Wed, Dec 12 2018 8:13 AM

Thanks Craig. I could find the problem related to unrecognized 7" records. It was simply the spring that should press the corresponding button on the arm contacts board which was not low enough to be effective. Sorry I didn't took photos -I will do tonight- but it is the first button from right on the board (the only in grey color in my 4000, others are red).

A little bent on the spring, wich is flat on below contrary to the others that have a 45° angle shape, cured the issue.

But I have another question: when I keep press forward manually, the arm travels across all the rail (and this is correct) but does not have a safe-stop at the end.The arm motor keeps turning until I hold the key pressed, even if the arm it's at the end of the rail. 

Shouldn't it have a safe-stop at the end of the rail? In auto-mode everything is fine: arm stops, lifts and go back.

 

Roberto

Velvet
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Velvet replied on Wed, Dec 12 2018 10:51 PM

Just to complete, time for final adjustments before connecting to an amp...

- re-checked motor supply voltages, frequency and distortion. I lowered voltage to 6,10 volts @33rpm just (manual says not to go over 6,5V so I guess

6,1 it's a safe and good voltage). Clean sine-wave, no distortion here.

- checked arm alignment, adjusted arm height, and zero-balanced it.

- adjusted 7", 10", 12", start  and stop button-springs positions and tested with different records.

 

Here testing the BG 4000 with a 10".  

 

Late enough here, so will enjoy a good rum. Goodnight

 

thch
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thch replied on Sat, Dec 15 2018 10:36 PM

Fantastic pictures. I had one of these BG's many many many years ago, in fact it was my first Bang&Olufsen item. I regret I sold it.

I do, however, prefer the 8002 now - much easier to maintain due to less electronics :-)

 

sonavor
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From the last two pictures it doesn't look like the cartridge mounts/mates to the tonearm connector correctly. Is that something you were planning on fixing?

-sonavor

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