I am truly saddened to report the Beomaster 4000 was taken out of service today after less than two weeks on the job.  Don't know when it happened, but after some switching of this, and rearranging of that, I have isolated a problem to the BM 4000:  the output of the right channel is substantially lower than the left channel, and the frequency response of the right channel is noticeably lacking in bass as compared to the left channel.

I took the top lid off and hoped to find an envelope and did!  Shown below is one side of the included schematic.  There is a service note bottom center which reads:

Replaced 6-15-81: TR57, TR58, TR-54, TR-56, TR53, #563, 564, R568, D576, D562, R569

JLH Upstairs Audio, W. Col. SC

The insides of this baby look too daunting for me to handle.  Unless someone else has a better idea, I'm boxing her up and shipping her off to Atlantic Systems come Monday morning.

Sorry to hear that Rich, hope you get your baby up and running soon without to much problems and costs

Capacitors would be the first thing to check.
See if one or more of the large cans near the transformer (large metal lunchbox) is leaking or bulging, it's
visible from below with the bottom plate removed.
Next, replace the capacitors on the amplifier board, that's the center board carrying two
identical but mirrored circuits.
A cap kit is available but if you still don't feel up to the task I agree that you should leave it to someone who does.
I only heard good things about Atlantic Systems.

Martin

OH RICH!!!

Rich:

Don't know when it happened, but after some switching of this, and rearranging of that, I have isolated a problem to the BM 4000

It doesn't sound like it was a "sudden" difference... but it happened after rearranging? I assume you removed all the extra sources and just tried the tuner if you have determined it to be at the BM?

The BM and the BG were always a complete set since bought new. It would be a shame to break them apart after so many years together, but...

1.) Should you wish to return the BM for a full refund -no problem!

2.) If you wish to have it serviced and keep it -I will be happy to work with you as well!

You just let me know!

P.S. Interesting note on the schematic -I never noticed it!

burantek:

P.S. Interesting note on the schematic -I never noticed it!

I think its an update done for the end stages, I saw a note about it in the manual onsite. Anyway good luck Chris

burantek:

Rich:

Don't know when it happened, but after some switching of this, and rearranging of that, I have isolated a problem to the BM 4000

It doesn't sound like it was a "sudden" difference... but it happened after rearranging? I assume you removed all the extra sources and just tried the tuner if you have determined it to be at the BM?

No, the rearranging was after I noticed the fault.  Thinking back on the setup, the problem may have been there all along, but I was blaming the cheap switch box from Best Buy.  But then again, I played mostly records since the setup, and the BG4002 is hooked directly to the BM4000.  I didn't notice a problem with records until June 7 at the earliest.  Who knows, but you're right.  Wasn't a sudden difference.

Will take off the bottom per Martin's suggestion and see what I see after work tonight.

Hello Rich,

I recently bought an BM4000 and it had very weak output on both speakers.

Reason was - as you could imagine - a cap problem. The 5000u / 70V had a measured 0.12uF capacity left.

Looking at the bottom it was clear it had vented...

I still haven't received the spare parts but using a 470u/100V (biggest cap I had with >=70V) brought life back with lacking bass of course.

Could it be the same with your channel? Would you be able to swap the caps from left/right channel to check?

And you could check with a (higher-impedance, not 8 Ohms or so) headphone as this would be less critical with output cap.

Good luck,

  Gunther

Dillen:

Capacitors would be the first thing to check.
See if one or more of the large cans near the transformer (large metal lunchbox) is leaking or bulging, it's
visible from below with the bottom plate removed.
Next, replace the capacitors on the amplifier board, that's the center board carrying two
identical but mirrored circuits.
A cap kit is available but if you still don't feel up to the task I agree that you should leave it to someone who does.
I only heard good things about Atlantic Systems.

Martin

The three 5000 uF caps near the transformer all look OK from both above and below. 

The amplifier board, however, is failing.  (Note:  the picture below is rotated about 180 degrees from the circuit diagram.)  The following caps all have a tan to reddish brown residue on them:  484, 452, 425, 421, 574, 542, 515, 511, and 557.  I assume this is evidence of leakage, though it seems a bit illogical the residue would make its way to the top of the caps.

Also, cap 441 (0.1 uF, 250 V) - the green one in the upper left of the picture - seems to have some evidence of overheating (carbon scorching?).

If it were just a matter of replacing a dozen or so capacitors, I'd be eager to tackle this task myself.  However, by my count there are 59 (!!!!) wires soldered to this board.  Most, if not all, would have to be desoldered to get this board out and turned over to desolder the caps which need replacing.

I am not going to chance it with so much desoldering of wiring.  This downed BM4000 is going to a professional.

Thanks to everyone who offered advice and/or condolences!  Beoworld comes through again. 

Losen the input/output board that partly covers the solder side of the amplifier board and swing it aside.
The input/output board is held only by a couple of countersunk screws near the DIN sockets at the rear.
This way you won't have to desolder anything but the caps.
And those caps are bad. (A kit exists for this).

BTW, interesting to see that you have the amplifier version with the four extra trimmers.

Martin

Dillen:

Losen the input/output board that partly covers the solder side of the amplifier board and swing it aside.
The input/output board is held only by a couple of countersunk screws near the DIN sockets at the rear.
This way you won't have to desolder anything but the caps.
And those caps are bad. (A kit exists for this).

BTW, interesting to see that you have the amplifier version with the four extra trimmers.

Martin

Thanks, Martin, I will look at it again tonight.

Are the extra trimmers good, bad or indifferent?

here are the caps and result on my second Beomaster 4000. Origianlly had no sound out of the rt channel but after some fixing I now have a nice solid hum, but there are other mechanical switching issues as well. currently stored away and on the "to do later list".

Not a 4000 but the left channel just howled, hum would not be the appropriate description.

If you get set to removing the old electros dont be surprised to find a few leaking underneath. Just cause it looks good on top desnt mean it is.

Looks like a Beomaster 1600/1700.
Safe to say that one of those caps won't leak anymore.

I had a Beomaster 4400 recently, where a similar cap only had the cast
yellow bottom part and the foil roll left. The complete red top was found in pieces
here and there.

The fact that Richs Beomaster 4000 amplifier is the 6 trimmer version is
not important. Both versions are equally good.

Martin

I had decided I wasn't up to the task of fixing the BM4000, even it were just the caps on the amplifier board.  So I sent it on up to Benny Amina at Modular Electronics outside of Atlanta.  Benny is the authorized repair shop for the Atlanta B&O store, highly recommended by Jeff/Jaff/burantek, and the guy who supplied me with a retipped MMC4 last year.

I heard from Benny today.  He recapped the amplifier board, but he said the right channel was still lacking "bass and warmth."  He was going to replace all the output transistors, plus he found the tuner was starting to fail.  He was going to replace transistors in the tuner as well.  He has all the parts on hand and expects to ship the BM4000 back to me on Monday.

Since I had sent the BM4000 off to Benny, I decided my next project would be a selector switch.  I feel kind of spoiled right now with my NAD 7175PE (which is keeping the receiver shelf warm for the BM4000) - the NAD has the following inputs:

1. Tuner (it's a receiver so of course)
2. Phono (one input, but switchable between MM and MC; now hooked up to the BG4002)
   
3. Tape 1 (BC4500)
4. Tape 2 (BC2400)
   
5. CD (CD X)
   
6. Video (iPod docking station)

I suppose I could put the tape decks in storage, but what's the fun in that?    Or use the El Cheapo switch I bought last month.  I know I said I would buy a switch from Sounds Heavenly - and I may still do that - but again, what's the fun in that?

But have you ever tried to source the most important part of the switch, i.e., the actual switch?  I did find one eventually - for $199.  I passed.

But then I stumbled upon a thread at DIYAudio where a guy said several folks have mentioned repurposing an old parallel printer switch box as a source selector in a "passive preamplifier."

"Huh," I said to myself.  "I think I have one of those back in the 'computer junk box' in the garage."

Thus was born the BM4000 Tape1 Selector Switch project.

For those of you who grew up with networked, USB, and now wireless printers, back in the day we hooked printers up to our computers with 25-pin parallel cables.  Our motherboards came with (usually) one parallel port, so if you wanted to hook up more than one printer to your computer, you bought a switch box.

Inside the stained wooden box is the repurposed parallel printer switch box.  The hookup to the BM4000 will be in the middle.  The source components will hook up around the perimeter.

Look at that poor switch.  Have you ever seen so many wires?

Fortunately you can still walk into Radio Shack (how does Radio Shack still survive in its brick and mortar form?) and buy some 4-wire telecom wire and D25 male soldered connectors.

You can also get RCA plugs at Radio Shack. 

At Michael's you can get little pine boxes that you can stain and wax to look just like your audio rack.  You can also get little cards of sticky-back lettering at Michaels.

Here's the back of the switch.  Left to right:

1. CD X input
2. Not used pair
3. iPod input
4. RX 2 (spare/second turntable) input (will need an outboard preamp)
5. Output to the BM4000
6. Input back from the BM4000
7. BC2400 output
8. BC2400 input

It took longer to cut the wire and strip the insulation than it took to actually solder.

I wonder if there's enough room in the box for the outboard preamp.

Another shot of the front. 

The idea is to tear down the audio rack next weekend and finish it with wax - assuming I receive the BM4000 back from Benny.  There will be some adjustment of shelving.  The selector switch - assuming it works - will be mounted under the shelf the BM4000 sits on.  Put it all back together and be happy again. 

Nice second-life use for that switch and a nice project !
I think, I would have chosen shielded leads and connected directly to the switch rather than the DB25's.
Well, maybe you can add alu foil to the inside of the box to shield from noise etc.
but the telecom leads may still worsen the signal separation (capacitance between close parallel leads).

I'm sure, it will look wonderful. Where did you buy the wooden box ?

Martin

Dillen:

Where did you buy the wooden box ?

Michael's, a chain of craft stores whose clientele is probably 90% female.  It is marketed as a "photograph box" and sold unfinished as below for about $6.

I have a few of these boxes, two of which I finished to go with the stereo.  The one below obviously has all my phono accessories, and the other has 30 some cassettes in it.

The phono accessories box is on the rack next to the BG4002, and the other is a few shelves below next to the BC4500.

Rich:

The phono accessories box is on the rack next to the BG4002, and the other is a few shelves below next to the BC4500.

 

Ordnung muss sein, I also have some kind of box system.

The big appleton box contains all tools for electronics, on top of that, the Victorias Secret box contains my new multimeter, 1st to the right is a bucket I use for reuseable used parts, 2nd right is a desert dish I stole from the kittchen, containing parts from my down BM 901.

My son goes to DK to studie coming August, and if the fabric selector agree, I will use his room as my worhskop, I will then be able to place more boxes and buckets in sight.

Rich:

there are 59 (!!!!) wires soldered to this board

I just counted those on my 3000 and I find at least 65!!!

I hope your 4000 is returned to you ASAP.