BeoMaster4 wrote:

All right, I just picked up the unit from the audio shop, it indeed was the 5V supply. So, it is up and running now!

Just one strange thing, I can't measure any voltage across the power resistors at TP200/201. On the left amp I did measure voltage and adjusted R226 to 18mV. I just ran the amp at full volume and it works fine on both channels... so seems a bit weird.

Also, how should I go about doing the offset adjustment? I measured the voltage at the speaker outputs and it just jumps around, 1 or 2 mV up or down from 0. Is that ok?

Glad to hear it :-) Now have you replaced the trimmers? If not then do so next before you end up back to square one!

Not being able to set the bias current obviously suggests there is another fault somewhere and you need to get to the bottom of that before putting the amp to use or even working in other sections.

Step1 wrote:

Not being able to set the bias current obviously suggests there is another fault somewhere and you need to get to the bottom of that before putting the amp to use or even working in other sections.

Right. That's what I was thinking, so turning the trimmer a little to see if that changes anything might be a first step.

/  Johan

Replace the trimmer first. Then adjust.
If the old one loses contact, the amplifier will run astray and end its life in a big bang.

Martin

I replaced every components on the right channel, including the trimmers R226 and R200. Or are you guys talking about a different trimmer?

I tried adjusting R226 to get a reading, but all I get is 0V across TP200/201. Is this even possible if the amp works? I just played one track with it and it sounds just fine... (actually more than fine 🙂)

The measurement on the left channel (on which I only replaced the trimmers and caps) did give me the correct reading after a little adjustment.

I also swapped the tone control PCB from the "new" unit to my original unit, so now I've also got my bass and treble controls working once again, sweet!

Dillen wrote:

Replace the trimmer first. Then adjust.
If the old one loses contact, the amplifier will run astray and end its life in a big bang.

Those were already replaced according to the first post, hence my suggestion.

/  Johan

Johan, I tried making incremental adjustments to R226, but couldn't get a reading, no matter what position it was in.

BeoMaster4 wrote:

Johan, I tried making incremental adjustments to R226, but couldn't get a reading, no matter what position it was in.

Turn off the Beomaster and check if you have a reading in resistance scale on that test point. Sometimes resistor leads oxidize so that test probes don't make contact at all until you really pierce through to the copper.

Across TP200/201 it measures 0.8 ohms. (I checked the left amp for reference, gives the same value)

Could it be R225 that's the wrong value? I had a BM5500 where someone had put in the wrong value resistor in that (corresponding) place and I had similar issues.

That's about where I stop, and leave it to Mika, Martin or Olly.

/  Johan

Nope, R225 is just fine at 100 ohms.