The Workbench

Re: BeoMaster 6500 Power Supply Issues

srywrgnbr — Wed, 06 Feb 2008 10:55:53 GMT

I was looking at the wrong parts list :). The correct part number is B80 C3700/2200

I replaced the rectifier. The fuse still blows as soon as power is supplied. I unplugged P14 and P15 to isolate this part of the circuit - and still the fuse blows. Now I just need to find out what is shorting to ground....

Re: BeoMaster 6500 Power Supply Issues

srywrgnbr — Tue, 05 Feb 2008 01:08:57 GMT

After a little probing, it appears that the rectifier (D3 on the circuit diagram) is bad. According to the service manual, the part number is BA423.

I am having a bit of trouble locating the part. Does anyone have a suggestion?

Re: BeoMaster 6500 Power Supply Issues

auric — Mon, 04 Feb 2008 23:59:24 GMT

Hi:

Let me jump in here re: power supply hum because I have had experience with this on my BC 9500

This may have nothing to do with power supply aging.

1) It may be dirty AC current in your house wiring! Try taking this to your neighbour's home or to work. Somewhere far away from your residence to see if it goes away.

I had a very noisy hum on my 9500 and I even posted to this forum asking for a spare transformer. It turns out when I relocated, the hum went away!

2) The transformer sits on rubber grommets (or sleeves). These serve as shock absorbers isolating the vibrations caused by the AC induction in the core from resonating in the chassis. It is possible that they have dried out or that the screws holding the transformer is either too loose or tight.

3) Finally also check voltages in output of the power supply, the filter capacitors and bridge rectifier for normal operation. Compromised components could introduce high loading on transformer causing it to hum.

B&O used really nice transformers! Unless it has had bad case of over heating, they last!

Check first before investing in new transformer :)

Derek

Re: BeoMaster 6500 Power Supply Issues

Mico — Mon, 04 Feb 2008 21:18:28 GMT

Is there a replacement power supply existing? Is the original still available as parts?

My BM has the usual humming feature relating to power supply aging.

Re: BeoMaster 6500 Power Supply Issues

srywrgnbr — Sun, 03 Feb 2008 11:26:54 GMT

There are two resistors (one each) running from the negative terminal to the chassis. There is a single capacitor between one of the positive outputs to the adjacent negative output.

According to the stripes the resistors are both:

65300 (Ohm) with +/- 2% tolerence

In the picture I submitted earlier, you can see one resistor in series with the cap leaving the negative output (close up attached). The other resistor is similarly installed on the other negative terminal (no capacitor there), but difficult to see in the picture.

Not sure where you saw the second capacitor :)

Re: BeoMaster 6500 Power Supply Issues

Die_Bogener — Sun, 03 Feb 2008 05:25:07 GMT

The two "resistors" on the output terminals to the chassis ground are capacitors...

Re: BeoMaster 6500 Power Supply Issues

srywrgnbr — Sat, 02 Feb 2008 17:03:05 GMT

By any chance, do you have a photo of a 110V model?

Looking at the wiring diagram, the wires on the input side "appear" to be correct (for a 110 model). However, it looks like someone attempted "clean" the signal from one of the output terminals by running a cap to ground in series with a resistor (all of which I plan to remove).

-R

Re: BeoMaster 6500 Power Supply Issues

Die_Bogener — Sat, 02 Feb 2008 15:33:12 GMT

Probably the BM is still intact. The owner before had modified the power supply in the wrong way... the two coils worked against each other, the direction of one coil is wrong.

This inducts a high current in the coils and blows the fuse at once, but no current goes to the secondary part. Plus and minus is zero ...

So, if you change it exactly like Peter's foto, then it should work again

Re: BeoMaster 6500 Power Supply Issues

Peter — Sat, 02 Feb 2008 14:30:51 GMT

Yes - type 2332 .

Re: BeoMaster 6500 Power Supply Issues

srywrgnbr — Sat, 02 Feb 2008 13:50:55 GMT

Peter,

Is the picture you provided of a 240V version?

Thank you,

Rob

Re: BeoMaster 6500 Power Supply Issues

Peter — Sat, 02 Feb 2008 13:48:24 GMT

If you need anything, do feel free to ask!

Re: BeoMaster 6500 Power Supply Issues

srywrgnbr — Sat, 02 Feb 2008 13:38:41 GMT

Perfect! Thank you!!!

Re: BeoMaster 6500 Power Supply Issues

Peter — Sat, 02 Feb 2008 13:25:47 GMT

This is what the 5500 looks like!

Re: BeoMaster 6500 Power Supply Issues

srywrgnbr — Sat, 02 Feb 2008 13:10:33 GMT

Thank you for the quick response. I have attached a picture. I do not have anything to compare it to, so I do not know how "modified" it is.

Re: BeoMaster 6500 Power Supply Issues

Peter — Sat, 02 Feb 2008 12:31:38 GMT

I don't have a 6500 but I do have a 5500 that I can take apart. If you do a picture of the bit you want, I will do a picture of the same part on the 5500 if that is useful.