Not sure if anyone has patience or interest to follow my struggle with the Beomaster 1000.. This may develop into the most annoying thread here.. But I have myself learnt alot from similar threads to this one, so I am sure it is not solely for my own profit.

Today after some small checks I connected it again. There were lights and there was no smoke! But I had no sound, complete silence. There may possibly have been a short from a broken cable on the bottom side of the board.

Then I tried to check the measurements according to the service manual, points J, K and I. In this I was probably not very successful, I found a few hundred millivolts over AD149 I and II. I found nothing on the potentiometers 675 and 731. If one is supposed to measure directly on them I don't know but I think so. Experimenting a bit I found 36 volts over the AC part of the bridge but nothing on the single pot for DC potential..

But if anyone has the time and patience to give me some hints about how to measure these points, I will be very interested to hear. It says you should measure K with respect to ground, that is chassis I think, that should be rather straightforward, but how come I get zero? And point J, it's not so easy to know where to put the probes. And sometimes you are supposed to measure with respect to ground and sometimes not, how do you know?.

When one measures points like this from a schematics, does anyone have some advice? These are very important things to do correctly, and I think many amateurs dabbling in their own machines would be interested to know.

All voltages specified are negative with respect to chassis, means chassis is +, but if you have a digital multimeter you will see - voltages if negative DMM is connected to chassis, be careful and select AC or DC when measuring, at point K you should get 30 V DC adjustable with trimmer 1K (906). If not search for failures before this point.

Without correct voltage at point K you cant do anything before this is established

All voltages on the drawing is negative in respect to chassis, measured with tape on, volume at "0", dont do anything to the FM tuner or stereo decoder before you have everything else working

Reading your manual and drawing, test points and how to is described there.READ YOUR MANUAL

Hi Jeppe,

I'm contemplating this BM 1000 as my next restoration project.

How does it sound?  Did you get yours fully working?  Anything special to be cautious about?

Thanks!

Hi Jeppe,

I'm contemplating this BM 1000 as my next restoration project.

How does it sound?  Did you get yours fully working?  Anything special to be cautious about?

Thanks!

Hi Jean

here my thread, white key versions has germanium TRs, some early black key versions also I think, volume, tone control and balance poties are difficult to clean, my volume poti is still acting up, have a used one from Martin and will change it when time allows

I found 4 different schematics for these, so get the right one

Hi Jean,
It has been a very interesting restoration project, I wish you best of luck. Maybe we can share our problems in this thread?
I am continuing with mine. Actually I have two BM1000 that I want to restore, but so far I am working on one. It goes slow because I only do it when I have spare time since this is a hobby.

I have another BM1000 which is almost unrestored and working (replaced the three largest caps), it sounds very nice with a pair of closed box speakers, warm and smooth.

It is a bit of hassle to disassemble it they say, and it could be, but I think this is not such a big problem. There are lots of cables underneath, I think I happened to melt the sheath on one with my soldering iron when replacing a capacitor, which caused a short, so be careful with that. I think it is quite straightforward otherwise. Yes, the germanium transistors are sensitive and prone to malfunction, but they are a part of the charm of this machine I think. I also bought a silicon version, but I haven't touched it yet..

The power switch has a muting switch too.

Martin

In late types the on/off knob operates not only the power switch but also a muting switch.
Is it working correctly?
Refer to the schematics and look into the Beomaster.

Germanium transistors are not particularly unstable. Not more than silicon.
And they are not that easily replaced by silicon transistors.
The bias (DC working point) is different - just to name the first obstacle.

Fitting an AC128 with a slim-line housing in a heatsink bracket for a standard housing, just filling the void
with  heatsink compound will not work.
The heatsink compound will not conduct heat on the scale needed. Far from.
Fit a suitable transistor or replace the heatsink bracket.

If the unit differs from the manual but appears untouched - believe what's in the unit.
If you are not sure, compare to a similar working unit.

The more you replace based on guesswork, the higher the risk of introducing more faults.
Don't get me wrong, but with the amount of work you've already done and components you've already
replaced, - some made better, some perhaps made worse - it makes
it next to impossible for us to take a guess at what could possibly be wrong.
The answer is most likely; A couple of things now.

If you have power supply problem - check the load for possible causes.
If/when the load is fine, repair the power supply.

Diagnose and repair.

Martin

Thanks Dillen,
I am honored to get your advice.

One problem is that the schematics are a mess, I have only one silicon BM1000 schematics version, it is not always corresponding to my machines. In this schematics I see no muting switch. Perhaps there is one in a silicon version schematics I have, but it seems to be a fully mechanical switch. Isn't it unlikely that a mechanical switch would somehow reverse it's operation suddenly. If there is an electronic switch I have yet to locate it.

What do you mean with 'check the load'?

One possible problem could be that I haven't adjusted voltages. Maybe if the 30V DC potential, according to the service manual, is too high this could cause symptoms like this? Or the bias adjusments, maybe.
I think it is a very odd symptom that sound is heard only when shutting off power. It intrigues me. Come to think of it, I have a Radionette receiver which displayed the same symptom, it was dead but I could hear weak sound for a second when shutting off. Replacing all caps fixed the problem. For this BM1000 all the caps have been replaced already though. Could it really be the big cap in the power supply.. (not replaced by me, by a pro, looks new).

The AC128's heatsink did get very hot, by the way, not fryingly hot but quite hot to touch. Maybe that's normal.

The load is what is loading the power supply = What the power supply supplies, amplifiers, tuner etc..
Which type and build series is this Beomaster?

Martin