The Workbench

Re: Beolab 4000 repair

stotty1111 — Fri, 11 Mar 2011 02:58:26 GMT

a 9va transformer would seem to fit the bill,

9/15=0.6amp=600ma

maybe a 14v secondary to give you your 0.625ma

i think both should work ok!

Re: Beolab 4000 repair

stotty1111 — Thu, 10 Mar 2011 17:10:59 GMT

ok, so the voltage after rectificartion is 23.5 which would have a smoothing cap in the circuit to give the 23.5 if divided by approx 1.45 this gives a transformer output of around 15v can you find one to fit with that output on the secondary, size may dictate the va figure, and from that you can get the ma output which would then give you a fuse value500ma would probably be ok as the stdby circuitry does not need lots of power

think that makes sense!

salut

Re: Beolab 4000 repair

Søren Mexico — Thu, 10 Mar 2011 16:09:22 GMT

stotty1111:

you sure its 24 v out? could be 12v out, which smoothed would be about 16.5v then no load situation would boost it/?

alternative would be a 230v unit with 2x 24v out in series to give 48v then with 120 onto the unit about 24 out

t

I'm sure, the repair manual says 23,5 V DC after bridge rectifier, and on the other speaker I have 23.6 V out with no load on the sec. coil, with 110-115V in.

230V/2x24v is a good idea, but space is limited and will have to make connections to the pins from PCB.

As the fuses are 650 mA, which size trafo can I use, 500 mA ???

Re: Beolab 4000 repair

stotty1111 — Thu, 10 Mar 2011 15:35:28 GMT

you sure its 24 v out? could be 12v out, which smoothed would be about 16.5v then no load situation would boost it/?

alternative would be a 230v unit with 2x 24v out in series to give 48v then with 120 onto the unit about 24 out

Re: Beolab 4000 repair

Søren Mexico — Thu, 10 Mar 2011 10:18:07 GMT

stotty1111:

In a ml mcl converter used as a passive amp i used a similar sized transformer ie as the original with a 12volt 9VA secondary, giving this has worked fine for the last 18 months!

I think the control circircuitry is fairly standard so should work in this app

tony

Secondary coil in BL 4000 is 24 V, I've been surfing for print transformer more or less same size, but no such luck, there is a lot of 230V primary out there but 110, 115, 120V nearly nothing, I think I need some 500 mA as the fuses are 650 mA, the space in the speaker is limited.

Most trafos I find is 1 or 2 primary coils and nearly all 2 coil secondary, with 2 coil secondary I will have to build something to get the solder pins to fit to the board.

anybody knows an US supplyer for print transformers, or a B&O dealer that sells spares ???

Re: Beolab 4000 repair

stotty1111 — Wed, 09 Mar 2011 03:18:22 GMT

In a ml mcl converter used as a passive amp i used a similar sized transformer ie as the original with a 12volt 9VA secondary, giving this has worked fine for the last 18 months!

I think the control circircuitry is fairly standard so should work in this app

tony

Re: Beolab 4000 repair

stotty1111 — Wed, 09 Mar 2011 03:18:19 GMT

In a ml mcl converter used as a passive amp i used a similar sized transformer ie as the original with a 12volt 9VA secondary, giving this has worked fine for the last 18 months!

I think the control circircuitry is fairly standard so should work in this app

tony

Re: Beolab 4000 repair

Søren Mexico — Tue, 08 Mar 2011 12:20:36 GMT

Anybody knows how many mA for the 1T1 trafo ??

Re: Beolab 4000 repair

Søren Mexico — Tue, 08 Mar 2011 12:19:11 GMT

Stand By Trafo, 1T1,

Re: Beolab 4000 repair

.......... — Tue, 08 Mar 2011 12:08:02 GMT

No problem! What is the STB trafo when it's at home? :)

Re: Beolab 4000 repair

Søren Mexico — Tue, 08 Mar 2011 12:04:47 GMT

Llewelyn:

If it helps I have a fault BL4000 complete PCB which I can send to you for test purposes? (Or to butcher?)

Llewelyn Thats a great offer, I will try to get something in the US or nearer by, but if its not posible I will come back to you, could you check if the STB trafo is ok ??

I just love this forum.

And Jaff, my windings are allready toasted, so toasted tortilla bits wont help

Re: Beolab 4000 repair

.......... — Tue, 08 Mar 2011 10:46:11 GMT

If it helps I have a fault BL4000 complete PCB which I can send to you for test purposes? (Or to butcher?)

Re: Beolab 4000 repair

burantek — Tue, 08 Mar 2011 10:35:06 GMT

Søren Mexico:

Jaff, waiting for a joke on this one

Now, where can I get a Trafo ???

Mexico... these should work!

Re: Beolab 4000 repair

joeyboygolf — Tue, 08 Mar 2011 10:07:24 GMT

The standby transformer for Jandyt's BL8000 cost him £34 from B&O. Should be similar for BL4000

Re: Beolab 4000 repair

Søren Mexico — Tue, 08 Mar 2011 09:36:39 GMT

tournedos:

That was entertaining, Jaff!

Søren, do you mean the primary winding is bad (shorted, or...)? That should be enough to blow the fuse without any other problems present. If the speaker had a bad short somewere else on the low voltage side, I believe it would've burned the rectifier or something.

If you want to be sure, you could of course swap the good transformer from the other speaker into the problem unit and try it. It'll either work or blow the fuse...

Sorry for the confusion, yes its the primary winding, measuring with all plugs disconnected and fuses out, on the good BL, I get 585 ohms on one winding and 604 on the other, on the bad one I get 275 ohms on one winding and no connection on the other (the one connected to F4, the fuse that blows), the bridge rectifier and RL1 shows same readings on both BLs, S1 works without problems (On-Off checked some 20 times)fuses F1, F2 OK, 0T1 gives 23.6 V out with 114 V in, and 24.5 V out with 118 V in, I have the BLs normaly connected to a "no break" with voltage regulation +- 5 %.

Now, where can I get a Trafo ??? B&O here in Mexico only sells equipment and I dont want to leave it for repair, as they are going to change the whole PCB and probably more, and charge alot of green backs for it.

Jaff, waiting for a joke on this one (the 3000s arrived safe to McAllen)