joostdeclercq wrote:

It seems that that PCB is dual layer.  Is it difficult to solder, or are there soldercontacts on front and back of the PCB?

It was pretty hard. It has a lot of copper and the pads seem pure round without "unweighting" or whatever it should be in English... which means that the heat runs away from the pads and you end up getting even the nearby components uncomfortably hot before the solders melt through.

The good news is that all the electrolytic caps you'd like to replace are axial, which means you can just snap them off with cutters and do one lead at a time, or just let the old wire ends stay on the PCB and solder your new caps to them. I actually used miniature radial caps on mine, there's just enough space that you can install them lying down. Be careful not to create shorts to the metal shields, though.

Hi,

Thanks for the tips. 

I ordered some new trimpots for the no-load current, but they were the wrong size :-(.  I checked the existing trimpots and the current was almost 11mV, as required.  I additional adjusted them, to match exactly the 11mV.

But the hum stays present.  I additional checked the 5V Power-supply as stated in the service manual.  I measured 7,3V between pin 2 and 5 in P14, where it should be 5,1V.  So, I guess there's a problem.

The servicemanual states that the current should be adjusted by disconnecting or shortcircuiting 2J38 and 2J38, but I don't exactly know what they mean by that.

Can anybody help me?

Kind regards

Joost

Joost,

Please don't get me wrong but unless you are an educated tech guy I suggest you
leave servicing of stereo equipment to someone who is.
You not understanding the instructions given in the service manual and not knowing
how to solder a multilayer PCB points in the same direction.
In my opinion, a Beomaster 7000 is not the one to practice on.

You don't state where the humming is coming from. Is it from the Beomaster physically
or from one or both speaker(s) ?
- If from the Beomaster physically, you can replace everything inside the Beomaster
without getting rid of the humming.
- If from the speakers, something more drastic is wrong with the Beomaster, which
should be attended only by a prof repairshop. If you feel ready for the
task, put an oscilloscope to the signal path. Do some stops along the path,
like the source selector, tonecontrol and volume IC's, the preamp etc. and let
us know your findings, that will help us help you.

Also let us know if the humming is present on all sources and if it's a
50Hz or 100Hz hum. An essential thing to know if we are to guess at a reason.

A readout of the Beomasters main power consumption in idle would also be good.
This will tell us if something inside is drawing too much current.

You can also put a distortion meter to the output and a signal generator to
an input and let us know the results.
This can help us determine if f.e. a transistor in the output stage is defective.

Martin

Yesterday, I just finished replacing every electrolytic capacitor (plus a couple of film caps) and every single trimpot on a customer's treasured BeoMaster 5000 - close enough to the BeoMaster 7000.

Exactly 2 trimpots and 3 capacitors did NOT need to be replaced.....

So, all were done anyway - no need to be cheap here, and I'm certainly not cutting corners.

Point is, that sooner or later, on this entire range of BM's (5000 thru 7000), the work is going to have be done properly. Just changing a cap here, or a trimpot there, is not going to solve anything.

Here's what came out of the BM5000.

Most of the original caps were made by Marcon - the forerunner of today's United ChemiCon, and of course the gold and blue ROE caps which are still around today under the Vishay banner - Roederstein and BC Components.

I chose to use Wima MKS2, Panasonic FM, and FC in the signal and audio paths, and Nichicon PW in the power section, and of course, my favorite Vishay BC 138 for the axials.

For the trimpots, I used Bourns 3352E Cermet units.

I haven't got all the parts for it yet - I'm waiting for Martin Dillen's package to arrive, but shortly, I'll put a full thread up on the overhaul of this, a BeoCord 5000, and 2 S55 Speakers.