Hi Alf,

It could be related to the Microcomputer board. My advice there is to keep in mind that there a lot of strange problems related to that board that have to do with connections, traces, etc.

I recently got a couple of my spare, non-functioning BM8000 Microcomputer boards fully working again by going through them several times checking traces and connectors. On one of the boards all of the continuity checked good yet some of the source switching operations were not functioning. The remote control did work so the natural assumption was that the keypad was the problem...but the keypad worked with other Microcomputer boards so it had to be something on the Microcomputer board. I eventually discovered that one of the Phase signals (that control the keypad button selection) from the Display board was not making its way to the Microcomputer board. Even though that three pin board connector tested good I replaced it and its three mica capacitors with new components. Everything worked after that. Checking the removed components...they all measured good. But replacing them fixed the problem. That is the type of thing you can run into. 

I wouldn't want to try and guess what the source of your BM8000 problems are but you just have to go through things methodically.  You can really benefit from having a known good set of BM8000 components to swap with in isolating the problem.  That is why I created and use my BM8000 workshop unit.

John

Thanks for your sobering words John, I hear you.

that is basically what I was trying to explain to my friend - erratic is not a 'black&white' fault picture !

although I spent a lot of time on his BM there are still "uncleared landmines" which we are now discovering 😢

i will look into a couple of areas incl that processor board again, possibly trying to swap that with a spare one

which hopefully works. 

Thankfully his processors are passing the test and that is at least something positive.

hope to report back with better news.

Alf

Thanks for your sobering words John, I hear you.

that is basically what I was trying to explain to my friend - erratic is not a 'black&white' fault picture !

although I spent a lot of time on his BM there are still "uncleared landmines" which we are now discovering 😢

i will look into a couple of areas incl that processor board again, possibly trying to swap that with a spare one

which hopefully works. 

Thankfully his processors are passing the test and that is at least something positive.

hope to report back with better news.

Alf

Problem no. 2 rings a bell : I remember I had a similar problem with the volume changing abruptly at about 2.8, with clipping light on, only on the left channel. I was going crazy since the problem was not present in service position.

The volume would also change abruptly between 1.3 and 1.2. And 0.0 was definitely not 0.0. Does yours also behave like this?

I found out that on the bottom left of the power supply board, there is a pin (P47), with a red wire attached, that goes to the display board. When the front panel was closed, it was touching one of the pin related to the digital volume regulation of the left channel, on the back of the microcomputer board. (One of the pin of P83 on the microcomputer board.)

What was happening is that the second Most Significant Bit was always at a fix value since it was touching a pin below, on the power supply board. Thus, the volume would change abruptly from 1.2 to 1.3; 2.8 to 2.9; 4.4 to 4.5.

Hope that helps

Guillaume

Many Thanks Guillaume,

that has indeed crossed my mind but been disregarded in the end in search of something more "serious" 🙄

but now "reinstated !!

it is exactly as you described !! 🤬🤬🤬🤬

will follow up straight away - again, thank you so much

Regards

Alf