Issue With Bang & Olufsen Beomaster 3500

amplifiers, receivers and loudspeakers
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Joined: 02 Mar 2019 15:45

Issue With Bang & Olufsen Beomaster 3500

Post by theoneillster » 11 Dec 2019 03:18

Hi all,

I have a strange issue with a Bang & Olufsen Beomaster 3500 receiver.

I bought it about a year ago, fully serviced, with the matching Beocord 3500 and Beogram CD 3500 units. It has been working beautifully until today, where it shut off out of the blue, and will not turn back on. What happened was, I put a CD in, went to turn the volume up, and the receiver froze at volume 72. All of the lights on the CD player went off for about 5 seconds, then none of the controls worked. It then proceeded to turn off, and go into stand-by mode.

However, the red power indicator light on the front panel remains lit. It is almost as if it is in permanent "standby" mode, and will not wake up. The cassette deck and CD player work fine independently. It should be noted that the remote control also does not work, for any of the units.

I have already tried the old unplugging-it-plugging-it-back-in approach, and removing the glass panel, as possible friction may have occurred.

Any idea what (could) be wrong?

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Joined: 14 Nov 2019 07:26

Re: Issue With Bang & Olufsen Beomaster 3500

Post by UsableThought » 11 Dec 2019 06:41

Hopefully someone who's really familiar with this system will comment. However a few thoughts -

As you've probably already concluded, having a CD playing in the CD player at the same time the receiver "froze" seems likely to have been purely coincidental. It might seem odd that the remote would stop working along with the receiver . . . except if the receiver has information programmed into it that the remote needs to be able to read to work properly. Just in case you could check the remote to see if it has a battery, and if yes replace it. However a dead battery in the remote wouldn't answer the question of why the receiver is acting up, so this wouldn't be my first choice of action.

Thinking now about for the receiver - one thing that could be checked is whether the internal mains fuse blew (though I don't know if you'd still see the red panel light if it had). A PDF of the service manual for the 3500 is available here at VinylEngine; use the search box to locate it. Page 12 of the PDF describes 3 different specs for internal mains fuses but nothing more than that. You might be able to go through the parts tables & diagrams in the manual to find the fuse locations, but often it's quicker to just open up a unit & look. If you're not experienced at taking electronic gear apart & safely working on it, you'd probably want a qualified person to do this for you. Rather than replace a mains fuse willy-nilly, it's best to first make sure of its status - a visual inspection doesn't always reveal a failed fuse, so a multimeter becomes necessary. If a mains fuse were blown, that would raise the question of why. A voltage transient in the mains power? That starts getting messy to think about. You could just replace a blown fuse & see if you get lucky.

Beyond that, if you go through the service manual, you'll see on p. 9 of the PDF that there's a reference to "replacing the lithium battery in this set." It warns about being careful with this battery & says to look at page 3-5 of the manual for more info. Page 3-5 of the manual is p. 34 of the PDF; take a look there & you'll see that a 3V lithium battery is indicated as part number "B1".

It seems highly possible that this 3V lithium battery could be the issue. I did a Google search for "Beomaster 3500 fuse" and immediately came across an old thread at the forum where someone mentioned that the 4500 has exactly such a fuse . . . and it can fail . . . and it is not only internal, but has to be desoldered to be replaced. Scroll down on that thread & you'll see the comment - here's an excerpt:
Now to be serious...  If it's not the fuse, it's often the memory battery in the Microprocessor can.  If the battery dies, the unit won't turn on. It is a 3volt lithium battery that is not user replaceable.  It has to be de-soldered to be replaced. If you have the red stand-by dot but it won't turn on, that's the most likely problem. The 4500 is pretty simple to repair. 
So maybe what applies to the 4500 also applies to the 3500? Someone with experience with these units should know. As for how to locate such a battery, again, if you're not a DIY type already, you may want to get someone qualified for this task. Otherwise, if you were working by yourself, you could make note of that "B1" part number for the battery & start looking very closely at the board layout diagrams & parts diagrams in the manual; in one or more of those diagrams you would probably come across B1 and that would be your battery. If you're experienced at this sort of thing, it's often quicker to just take the unit apart (safely so as not to get shocked, and with the right tools, not breaking or losing anything) and look for the battery that way (and any mains fuses too while you're in there). Usually such parts are obvious to an experienced eye. Also, if desoldering is indeed involved, desoldering a lithium battery requires care - heat can cause such batteries to explode.

Lastly, have you looked through the user manual to see if it offers any troubleshooting hints? I don't see it here at VinylEngine, but there seems to be a site that does have it: ... er%203500/

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