You may need a software update in the 5500. Earlier ones don't work in the same way as the 6500 - I had exactly the same issue when my 9500 was stolen and I was given a 5500 by my dealer as a stand in. Exactly the same issues which were fixed by getting a 7000!

OK, thanks - in that case I'll probably solve the issue by not installing the 5500 in an MCL setup 😕  After posting, I had the sense to try with an MCP6500 through MCL (and putting an oscilloscope on the data line) and the BM isn't responding in any way on the MCL. In addition, it is only the long "all-standby" command that goes through.

The type sticker in the rear says SW 2.3, can anybody confirm whether this is too old for a link setup? It seems that this just might be an electrical problem as well (blown buffer transistor or a faulty MCU) but I'd rather not bother investigating further if it isn't going to work without an update anyway.

Funny that the Beomaster should be that old - it is white, and I thought that was a late addition in the series.

In Beocenter 9000s the Datalink support is indicated by a sticker on the rear panel. In my case there is the Datalink sticker but no software version, perhaps the original models (without Datalink) have software version sticker and after update it's replaced by the Datalink sticker?

I got a MCL manual saying the serial should be after: 05101264 for being ready for Beolink.

If not the 4IC4 needs to be changed. Order number: 8341051

Beolink label follows the IC and should be put back on the Beomaster when installed.

Friedmett wrote:

I got a MCL manual saying the serial should be after: 05101264 for being ready for Beolink.

Great info, thanks. This is s/n 0682xxxx, so it might have a fault after all. Have to look into it. I guess the part number will be on a sticker on the ROM chip, so that should tell it for sure...

Well, what better way to pass time inbetween cooking than opening Beomasters. So here is the CPU module - and clearly the updated software ROM is there, so there must be some other problem.

Too bad the processor is not socketed, so I will not just try replacing it although I have 8031's laying around. TR3 on the preamp module will be attacked next unless I starve to death first... 😕

There was no need to dig in the middle... I put the scope straight on the relevant port pin of the processor and the data from the MCL came cleanly all the way there. Nothing out in return, though. It could be that the output function of the 8031 port pin is damaged - but that still doesn't explain why the all-standby command goes through and is understood by the CPU, but nothing else is.

I could take the CPU to the office to meet the rework station and try another chip, but that would risk ruining an otherwise perfectly good Beomaster... I think I will close it up, clean this mess and just not care about the MCL... the attempt was purely out of academic interest to begin with 😁

Could it be a tranciver error?

Maybe the wire connection in the relaybox is not good enough?

No, I don't think so - as I mentioned in the opening post, all that stuff works just great when I connect it to the BS6500.