Hello everyone. I recently acquired my first non-turntable piece of B&O equipment, a Beomaster 1000 (later version, with gray faceplate). When tried, it worked fine, but FM refused to come in as stereo. After some digging around, it was discovered that, underneath the phono preamp board, a 'dummy' plug was fitted where the stereo decoder was supposed to be. I was under the impression that the gray faceplate BM1000s were equipped with stereo multiplexers, and mine indeed has the green stereo lamp on the left side of the dial (which lights up in every mode except FM), but no multiplexer! How could this have occurred, and is there a source for a proper stereo decoder for this unit? Thanks in advance!

-Adam

A stereo decoder was optional and far from all Beomaster 1000's got one.
The optional boards are quite sought after so be prepared to pay a little for one.
The RIAA board in your Beomaster is also an option. Slightly rarer than the stereo decoder, actually.

Martin

Dillen:

A stereo decoder was optional and far from all Beomaster 1000's got one.
The optional boards are quite sought after so be prepared to pay a little for one.
The RIAA board in your Beomaster is also an option. Slightly rarer than the stereo decoder, actually.

Martin

 

Looks like I was mistaken, then! I'd figured the gray faceplate meant that all the upgrades were built-in, but this one is type 2312, and according to the Beomaster 1000 page on this site, the stereo decoder wasn't included by default until type 2317. Wonder why it took so long for them to decide to include it by default. Is there any sort of source for the decoder, apart from a parts 1000? Otherwise, might it be possible to retrofit a modern FM multiplexer, such as the Kemo B127, to fit the existing connector?

Forgot to mention earlier: When I got my Beomaster 1000, one of the knobs was missing. Is there a known source for them? Again, thanks in advance!

-Adam

Unfortunately I've never seen a single MPX decoder on sale, at least not on fleaBay. You might get one from a fellow Beoworlder, but I suppose a more likely source is a donor unit. I believe the decoder from a BM900 would electrically be a drop-in, but the bracketry might need work?

I'm sure it would be possible to get the Kemo kit to do the job, but it may need some interfacing and level shifting as the Beomaster supply voltages for example are quite high even in the small-signal sections. That'd be relatively easy, but I'm not sure about the signal levels. That would be a nice project though, as there are a lot of BM900M/K owners with the same problem. I guess there were still a lot of countries that didn't have regular stereo broadcasts in the '60s, so it made sense to keep the base unit price lower and the decoder as an option.

Martin, with the RIAA option, do you mean the preamp for the second phono input? I thought the first one was always there.

tournedos:

Martin, with the RIAA option, do you mean the preamp for the second phono input? I thought the first one was always there.

Thats what I thought too. You have two Phono connections. One with a RIAA and one without. As you can get 2 different Beogram 1000's. One with a RIAA built in the other without.

Craig

tournedos:

Unfortunately I've never seen a single MPX decoder on sale, at least not on fleaBay. You might get one from a fellow Beoworlder, but I suppose a more likely source is a donor unit. I believe the decoder from a BM900 would electrically be a drop-in, but the bracketry might need work?

I'm sure it would be possible to get the Kemo kit to do the job, but it may need some interfacing and level shifting as the Beomaster supply voltages for example are quite high even in the small-signal sections. That'd be relatively easy, but I'm not sure about the signal levels. That would be a nice project though, as there are a lot of BM900M/K owners with the same problem. I guess there were still a lot of countries that didn't have regular stereo broadcasts in the '60s, so it made sense to keep the base unit price lower and the decoder as an option.

Martin, with the RIAA option, do you mean the preamp for the second phono input? I thought the first one was always there.

I'm guessing that a pull from a Beomaster 900-type is my best bet for an original, but I have no real idea. I have a friend who uses the Kemo kits to serve as stereo decoders in European table/console radios, which makes me think that option could be made to work, but I don't have a service manual, so I don't even know how it'd be wired in. Your theory about some countries not having stereo FM makes sense, since B&O doesn't seem to have made separate versions for different countries, like Grundig and other countries did (could be wrong, of course). BeoWorld's page on the BM1000 only lists two type numbers (2316 and 2317, no mention of 2312), with no distinctions given between them (other than to say that the 2317 included the stereo decoder). BeoCentral's page lists six type numbers for the BM1000, again, none of which are 2312. 

With regards to the phono amp portion, BeoCentral's page on the BM1000 has this to say: "Two record players could be connected, initially both of the type with ceramic pickups, though an optional preamplifier could be fitted inside the Beomaster so that a B&O magnetic pickup could be connected directly." This concerns the original white-face version, and while mine has a black faceplate, it also has some germanium transistors, which were supposedly eliminated with the advent of this redesigned BM1000 in favor of silicon types, so it makes me believe that this is an earlier version which was retrofitted with the newer cosmetics and phono pre (but, sadly, not the stereo decoder). I'll have to perform some tests to see whether or not both of the inputs are suitable for a magnetic phono cartridge.

Anyway, in the course of testing, another issue has shown up, a buzzing sound from the mains transformer. While it doesn't seem to have an adverse effect on operation, and doesn't seem to be transmitted through the speakers, it is nonetheless annoying. Might there be a solution to this issue? Yet again, thanks in advance.

-Adam

The type 2312 was an odd one, half a step from the early type towards the later.

The two phono inputs are of different levels. One is at line level (with no RIAA)
while the other is at "true" phono level with built-in RIAA.
I haven't seen the actual module but my guess is that the option installed is
a second RIAA for the line-level input, providing the BM1000 with two phono-level
inputs.

It's true that a BM900 decoder will fit electrically but the brackets are different,
there's an outboard transistor to fit somewhere and it's not all BM900 that
has a decoder either.
But don't give up. A donor BM1000 may provide you with both
a decoder, a knob and a replacement mains transformer (of which several different
types were used, according to the type and sub-revision).
I am extremely busy with other things right now but I may also be able to dig
something up come time.

BTW; Are you sure that the buzzing comes from the transformer and not the large
filter capacitor right in front of it ?
That cap is often bad and I replace everyone I've seen after seeing one that blew up
many years ago. Mount a good 2200uF 50V and it'll be fine.
Note the polarity of the cap, the BM uses positive ground.

Martin

Dillen:

The two phono inputs are of different levels. One is at line level (with no RIAA)
while the other is at "true" phono level with built-in RIAA.
I haven't seen the actual module but my guess is that the option installed is
a second RIAA for the line-level input, providing the BM1000 with two phono-level
inputs.

I think I have it in my BM1000 type 2317, since the short experiment with my BG1000 with built-in preamp overloaded both phono inputs, while it sounded fine when connected to the tape input. If you want, I'll take pictures of it when I open the Beomaster the next time. I replaced the dial lights right after I bought it, but didn't even know then that there might be something interesting in there!

I took a quick look at the schematic regarding the Kemo kit, and it would at least need an amplifier stage before it - the input level to the B&O decoder is only 0.2V, while the Kemo requires around 1V.

Dillen:

The type 2312 was an odd one, half a step from the early type towards the later.

The two phono inputs are of different levels. One is at line level (with no RIAA)
while the other is at "true" phono level with built-in RIAA.
I haven't seen the actual module but my guess is that the option installed is
a second RIAA for the line-level input, providing the BM1000 with two phono-level
inputs.

It's true that a BM900 decoder will fit electrically but the brackets are different,
there's an outboard transistor to fit somewhere and it's not all BM900 that
has a decoder either.
But don't give up. A donor BM1000 may provide you with both
a decoder, a knob and a replacement mains transformer (of which several different
types were used, according to the type and sub-revision).
I am extremely busy with other things right now but I may also be able to dig
something up come time.

BTW; Are you sure that the buzzing comes from the transformer and not the large
filter capacitor right in front of it ?
That cap is often bad and I replace everyone I've seen after seeing one that blew up
many years ago. Mount a good 2200uF 50V and it'll be fine.
Note the polarity of the cap, the BM uses positive ground.

Martin

I performed a test using my Beogram 8000 (the only turntable I have with a DIN connector) and a MIDI cable. From that, I can tell that phono 1 is almost certainly high-level, requiring the volume control to be cranked all the way up to get Walkman-level signal output. Phono 2, on the other hand, is definitely low-level, playing at a proper volume (though the MIDI cable doesn't make too great of a phono cable, resulting in mild hum, though it could just be picking up the buzzing from the transformer). One thing this stereo test tells me is that the balance control (well, I assume it to be such; the rightmost knob in the set of four) isn't doing much to the right channel. About the only effect it has is to cause the left channel to be louder than the right when it's turned all the way to the left. Yet another problem...

Hopefully, some sort of donor unit will come along. Granted, with the number of issues the unit seems to have, it might be better off as a parts unit, but who knows. This is the only Beomaster I've come across in my travels, and other than the problems, sounds pretty good. If you can find the parts I'd need, I'd be grateful.

I'm 95% sure that the buzzing is coming from the transformer itself. At the moment, other than the phono buzz, there's no hum whatsoever in the speakers. A friend of mine took a look at it, loosened the screws holding the transformer in place, and the buzzing went away momentarily. I'm guessing it's due to loose laminations, but I'm not ruling out an outside cause.

-Adam