General Forum

Re: Newbie with dead Beolab 4000

Ron — Mon, 28 Dec 2009 21:20:10 GMT

Well it took longer than planned but I fixed my dead 4000 and it sounds as great as ever. As it turns out I was able to buy B&O parts from a repair shop and also located a replacement STK amp module on line for $13.00.

Thanks again to all for your help - especially Peter who sent me the repair manual - invaluable!

Ron

Re: Newbie with dead Beolab 4000

Ron — Sun, 29 Nov 2009 16:01:37 GMT

Thanks to all for your continued help.

Graham, your points were valid and no offense (offence) taken - and your input on the prevaling attitude re: parts sales at B&O shops is appreciated. Also, thanks for the heads-up on the lack of location info. I should have done that right away as it always bugs me when such info is missing on several other forums I belong to.

Tony, the Conrad link is great and it looks like there may be some alternative transformers that might work if my local shop refuses to sell parts.

The good news in all this is that my destructive testing methods have only messed up the on/off/standby control function which, despite B&O's penchant for exotic parts, is a straightforward 23vdc power supply that, when an audio signal is present, energizes a relay which in turn connects main voltage to the audio, amps and speakers (which still work great) So if I'm unable to buy the B&O transformer my choices wil be either to let the experts repair (may do depending on cost) or go even farther over the edge and bypass the faluty power supply with a substitute. Will report back after I talk with the shop in the next few days.

Thanks again to all - this is a great forum!

Ron

Re: Newbie with dead Beolab 4000

stotty1111 — Sat, 28 Nov 2009 12:09:56 GMT

could be the standby transformer - ui had a similar(i think) problem withthe standby transformer on a bl converter- located one in the Conrad.fr site i used a 9v output unit which with dc smoothing gives a supply above the normal 12v - canmnot remeber the va output but can be id'd by the pin spoacings - hope thyis helps!#

salut a la finistere

tony

Re: Newbie with dead Beolab 4000

joeyboygolf — Sat, 28 Nov 2009 10:20:19 GMT

Not condescending at all, I'm simply informing you of the atitude that your dealer is likely to take whether you sign a waiver or not.

I don't know where you are in this world of ours but in the UK you will find that the vast majority of dealers and service agents will not supply you with spare parts under any circumstances.

It would help if you made use of the facilities for indicating your location.

Re: Newbie with dead Beolab 4000

Peter — Fri, 27 Nov 2009 17:49:14 GMT

Parts are a bit tricky to get hold of but are good value for money. Always worth asking your local dealer especially if he knows you. Otherwise it is a case of buying parts units - always risky!

Re: Newbie with dead Beolab 4000

Ron — Fri, 27 Nov 2009 15:20:11 GMT

Thanks for the info. For the record I'm not inexperienced, just clumsy in this instance. (Electrical Engineer with many successful, complex, electronics repair projects in the past) - and who doesn't mind admitting mistakes even at the risk of getting condescending opinions from people who don't know me

Will seek parts from my local service rep - even if I have to sign waiver.

If anyone else knows of a shop or individual who deals in used B&O gear I'd appreciate knowing.

Ron

Re: Newbie with dead Beolab 4000

joeyboygolf — Fri, 27 Nov 2009 14:48:14 GMT

You cannot buy B&O modules from anyone other than your B&O dealer. Given your track record so far, I guess that he is unlikely to sell them to you on pain of being sued should you do yourself any damage in future.

I suggest that you bite the bullet and hand the speakers over to the service department.

Re: Newbie with dead Beolab 4000

Ron — Fri, 27 Nov 2009 12:41:14 GMT

Back again with good and bad news on the "dead" Beolab 4000

Thanks to Peter's help I was able to isolate the problem to low standby voltage when in line (RCA jack) mode. Should be 23vdc but I have 15v. But while trying to trace the fault back toward the power source I accidentally shorted out the 120VAC input to the standby voltage transformer. I'm still working on it but it appears this unit is blown and it's a pcb mounted, B&O stamped part.

Unfortunately this episode may have also blown the output amp but I won't know for sure until I swap in the good PS from my other speaker.

So I've searched here for B&O parts sources but the results are not clear. Can anyone point me in the right direction?

Also, assuming the worst, are there sources for used modules?

Finally, as I'm still new here, let me know if I should re-post on the Workbench section.

Many Thanks,

Ron

Re: Newbie with dead Beolab 4000

Ron — Sun, 22 Nov 2009 14:55:02 GMT

Thanks Peter! - very helpful info - the symptom mentioned in your snippet is what I have.

By trial and error I'm focusing on the circuit that senses the presence/absence of audio and thus switches the unit from ON (green) to Standby (red). On my bad unit the presence of audio turns the LED green but does not energize the main relay.

There is a 4 conductor (3 gray + 1 red) ribbon cable from the main board to the Power Supply. Don't ask me how I figured this out but if I disconnect this from the PS board, and then jump the middle two pins on the connector, the relay fires and the speaker works perfectly. If I try this with the cable connected it does not work. Curiously, if I leave the jumper in place, then connect the cable and then remove the jumper the speaker stays on. But once turned off it won't come on again until the above sequence is repeated.

I've been searching for a source for schematics and component locators. How hard would it be to get me a copy of the relevant sections? If this is a lot of work could you point me in the right direction to order a set? What you sent me mentions "muting transistors" Perhaps what I'm calling audio sensing is called muting in factory lingo?

Thanks for the tip on the fuses. FYI, I did not check them yesterday as I found the above "fix" first and since the speaker seemed to work perfectly I figured the fuses were all OK. However I checked them today and both 63mA fuses are blown. However I think I may have blown them in my first attempts to jumper the tightly spaced pins on the connector. I swapped in good fuses from my other speaker and still have the same symptom. Curiously it does not matter whether I have good, bad or no fuses installed - the LED lights and the jumper "fix" causes the speaker to work well. Conversely, when I removed these fuses from my "good" speaker nothing works - no LED or any other sign of life. Go figure.

Anyway, I'm flying blind without the schematics so please let me know where & how I can get/purchase them and thanks again for your help.

Ron

Re: Newbie with dead Beolab 4000

Peter — Sun, 22 Nov 2009 03:50:17 GMT

I wonder if you arefortunate and you have merely blown a fuse. There are a couple of fuses after the power supply on the circuit diagram - I attach a snippet from the service manual!

Newbie with dead Beolab 4000

Ron — Sat, 21 Nov 2009 16:27:04 GMT

Hi everyone.......

I searched on this topic and found one thread (bad amp) Is there anyone out there who can help me diagnose my dead 4000? I had not used the set for a while due to broken (chewed) cables under the house but now that those are fixed one speaker is kaput. LED's seem to work as designed (I'm using RCA phono jacks and cables connected to pre-amp output from my receiver. ) Worked perfectly for many years.

Based on the other post I guess I could swap out the amps to confirm but am hoping there is more history on what to check for this type of failure.

Assuming the worst, are there sources for "civilians" to buy B&O parts?

Thanks in advance.

Ron