The Workbench

Re: Beomaster5000- turns off?

SimasCh — Wed, 08 Aug 2007 02:22:23 GMT

If it could help to lead me further in repairing the amp myself:

I remembered, that when I was disassembling the amp for changing the transistors, it was, of course, off the 220v outlet, but i somewhere short-circuited those big caps (on the line of power supply, I assume), and as they were still charged, they sparkled a bit. I didn't found exact place where they got that contact, but as soon as I can't see any voltage in end-amp circuit, I think it's the problem with power supply. Where to check?..

Re: Beomaster5000- turns off?

SimasCh — Thu, 02 Aug 2007 04:55:05 GMT

Hi, I need help again :(... I replaced potis and transistors (I used BDV67D instead of BDV65B, that was there originaly, but they are quite the same).

Although, the voltage between measure points disappeared at all. It's 0.00... How could it be?!...

Re: Beomaster5000- turns off?

Die_Bogener — Mon, 30 Jul 2007 07:06:14 GMT

Yes.

It is also possible to remove the 2 defect power transistors. Then you can check the other channel.

If the other channel is ok and music plays, then you know that power supply, tuner, controls are 50% ok.

The BDV64 / 65 are very old and rare, but good Hifi parts. Do not use other types for replacement!

But if it is possible to adjust the no load current and the amplifier is still stable, keep the old transistors. Watch it for some days and play some louder music. The problem is, that heat in the amplifier makes a higher no load current... causing even more heat and more current... until the system shuts down. If this has happened several times, these transistors have a damage and have something like a leak.

If you play loud music immediatly after powering up the unit, and the system fails after 2-3 minutes, then replace the transistors.

Re: Beomaster5000- turns off?

SimasCh — Mon, 30 Jul 2007 05:47:06 GMT

So, if I got you correctly, I firstly replace the potis, and if it doesn't help- the transistors TR1xx, yes?

Re: Beomaster5000- turns off?

Die_Bogener — Mon, 30 Jul 2007 03:41:16 GMT

Ok, you are on the right way...

78mV is too much, the power transistors BDV64/65 become too hot even in standby.

I would replace both potis... no problem, the bottom plate can be removed easily, there is no need to disassemble the boards.

The next problem is, that the power transistors TR1xx probably are already damaged, they should also be replaced. You can try first the potis, but watch the no load current. If a transistor has a small damage, this current increases more and more and both transistors become hotter and hotter... and then the master becomes instable and fails.

Re: Beomaster5000- turns off?

SimasCh — Mon, 30 Jul 2007 02:48:03 GMT

It seems I need help again.

I measured the DC voltage between those measure points you wrote (the same I found in the manual)- it's obvious that the problem is there, because between TP200 and TP201 there is almost 10 mV (~9,8), but between TP100 and TP101- ~78mV (!).

The problem is that turning those potis doesn't influence those values at all! I cleaned them, turned several times in one and another side but nothing happens- the voltages between those TP's doesn't change.

Re: Beomaster5000- turns off?

SimasCh — Fri, 27 Jul 2007 02:54:32 GMT

Whow, at last something to try! I definatelly will do it in weekend. Will let you know the results!

Re: Beomaster5000- turns off?

Die_Bogener — Thu, 26 Jul 2007 15:45:01 GMT

No problem....

That's why we are here.

Re: Beomaster5000- turns off?

Jandyt — Thu, 26 Jul 2007 14:48:39 GMT

Sorry Told you I'm not a Techie!

Andy T.

Re: Beomaster5000- turns off?

Die_Bogener — Thu, 26 Jul 2007 14:36:32 GMT

The BM5000 needs a replacement of the two potentiometer R126/R226 = 100 Ohm. With this parts the "NO Load Current" will be adjusted.

Measure from TP100 to TP101 (TP200 to TP201) a DC voltage of 11mV and adjust the potentiometers R126 (R226).

No speakers connected, volume=0, Radio P1-P9 activated, BM5000 cold (!).

The reason for this is corrosion, dirt, nicotin and 25 years age... quite normal.

The quick 'n dirty repair version would be: contact cleaner on these potis, turn them several times and new adjustment or even the same position as before... for 2 more years. Then the same procedure again...

Re: Beomaster5000- turns off?

Jandyt — Thu, 26 Jul 2007 14:22:09 GMT

Not being a techie but I think trimmers is a nickname for capacitors or caps.
These apparently don't last forever but are fairly easy to replace (I believe)
Martin (Dillen) is the guy to send a PM to and ask about cap kits.

Andy T.

Re: Beomaster5000- turns off?

SimasCh — Thu, 26 Jul 2007 01:18:18 GMT

Can you explain more about those trimmers?

Re: Beomaster5000- turns off?

SimasCh — Sun, 22 Jul 2007 12:38:12 GMT

Yes, it becomes quite warm in minutes the like you sugested...

Re: Beomaster5000- turns off?

Die_Bogener — Sat, 21 Jul 2007 11:23:45 GMT

Ok, then check with a louder level without speakers. If the coolers become worm or hot after a while or it turns off, then the amplifier is defect or needs adjustment. There are two trimmers for the current without load in the amplifier. These trimmers can go defect, simple oxidation...replace them.

Re: Beomaster5000- turns off?

SimasCh — Sat, 21 Jul 2007 05:21:10 GMT

No, the speakers are ok, i tried another pair and even checked the impedance.