ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
I was handed over a "if you can fix it, its yours" Beomaster 7000. It was told as a lightning damage, and it had been in at a shop, they could not fix it.
The only visible damage, is on the tuner board. Traces had been burned, and the shop had tried to repair it, very badly with traces stripped and wires soldered on the traces, instead between 2 good solder points at components. But never mind that, I took out the board, just so it would not cause trouble finding the other issue.
The unit appeared dead. No std.by light, and no click on the std.by relay. Mute relay clicked, but that was it.
First thing first, re-soldered the std.by relay, and now there was action with that relay, so far so good.
Started at the beginning, and measured voltages, all was fine all the way to processor and display board.
Before doing anything else, I took out a Beolink 7000, and behold, there was actually life.. 2-way worked, and status and volume was shown, but no lights or anything, and the mute relay and std.by relay did nothing with "mute" or "std.by" buttons. Both via remote and buttons on front panel. No action at all. But the processor seemed to work.
Looked at the schematic, and saw that the MM5450 LED driver on the front PCB, was actually also responsible for both relays besides the LED's. Took out the oscilloscope, and there was a fine clock signal to the MM5450, so before doing a lot of troubleshooting, I figured it was worth a try to change this IC.
Luckily B&O used this IC everywhere, and in one of my Arduino projects, I actually for fun, had control of the display and touch buttons for a CD4500 touch PCB.
But.. I also had the touch/led PCB's from a 8500 lying around, so took one of the 3 MM5450's from that and replaced the one in the BM7000. I figured it was a long shot, but success :) :) :)
The BM7000 is back to life with led's and front buttons, and both relays work again. Both via remote and front buttons.
So, step 1 done. Now I need to connect speakers and a cd player as step 2, just to check if the amplifier is working, and step 3 will be to try to fix the tuner board with better wire fixes.
I have a bad feeling about the tuner board, if they are as sensible as the 2300/ouverture boards, I suspect it to be dead, but I have to give it a go :)
Anyone have experience with these tuners, and lightning ? :)
/Jacob
BeoNut since '75
Well. not quite total succes yet.
Most IC's on the pre-amp was dead, as were 2 transistors, 2 diodes and 1 resistor.
There is sound in the left channel now, no sound in right, and volume cannot be controlled, most likely is the TC9177P volume IC, so need to get one of those.
TC9184P which is the tone control, is working, at least I can hear difference in treble / bass when changing.
The biggest problems was the following.
-40v on the -12v, changed TR8/9
-8V missing on pre-amp, changed 2 resistors(also the one for +8)
No light in LED's, changed MM5450 LED driver.
Changed source selector IC/LF353 and 4558's They all had -40v on them instead of -12. Just need the new volume IC, and I hope there is life again :)