I'm currently restoring a Beolab 5000. Just finished a complete recap - basically every single cap was leaking. After that it worked fine and I was rather trilled to find everything this flawless...until I tried to adjust the power supply. All voltages were way off, at the test point it was 72V instead of 60...

Basically everything in the power supply was dead. I'm really surprised the Beolab was still running more or less smoothly?! One 2N3055 and the ZF18 were short circuit, the 4039V1, SE7001, one SE8001 and the ZL33 were open circuit.

The latter one proves to be quite a problem. I just can't find one. Or a replacement, for that matter. I can't measure the current right now, but i suppose they put a 15W diode there for a reason. The highest rating zeners I can find are 2W. I considered just paralleling several of those, but since the breakdown voltage is never exactly the same I suppose that won't end well.

Any suggestions on what to use here? Or where I can get one?

Thanks.

Amp or Speakers?

Hallo Meise

My databook recommends the ZX33 as a replacement. Not easy to find but available.

If you have some commercial contacts: Bürklin has them, just checked...

If not I might be able to get them but depending on our next order that might take some time.

It says 12.5W BTW.

I have found some old ITT ZL22 in my fund but they won't be of too much help here

   Gunther

Danke! The ZX33 indeed seems to be at least somewhat available.

Spend the last hour desperatly googling for some supplier who doesn't have a minimum order value...and finally I did find one: http://www.littlediode.com/components/ZX33.html

It's not cheap and it'll take a week to get here - but it's something!

hemenex:

I have found some old ITT ZL22 in my fund but they won't be of too much help here

 Now what's up with those? Believe it or not - when I found the diode faulty, I remembered I had seen something similiar looking somewhere around...and...I found a box of ITT ZL22s.

stampfki:

Amp or Speakers?

Amp. I would never work on something as ugly as those speakers.

ablaumeise:

I would never work on something as ugly as those speakers.

And if I would have known you hate one of my preferred speakers you would have had to look for the ZL33 replacement on your own

Actually I've never seen one in real life. I'm sure they have their qualities...but either everyone that ever photographed one used a crappy camera or that is the most hideous fabric I've ever seen.

Back to topic: I ordered a ZX33, but they first have to check wether they actually have some...and even if they do it's going to take at least two weeks before it gets here. So if anyone has another source (or even the diode itself)...I really can't wait that long, I finally want to finish that Beolab.

Alright, the ZX33 finally arrived today - installed...and…60V and 33V - spot on. The power supply is working perfectly again. The left amplifier, not so much. *sigh* Yet another challenge.

Anyway, should anyone ever need a reference for a repair - substitute types used for the unavailable transistors are:

2N2102 for SE8002, BF259 for SE7001, BU406 for 4039V1. Watch out for the different pinout on the BU406.