Beomaster 8000 Type 1903 - Arizona Restoration Project - Replaced Microcomputer Board Testing

I decided to go with my already restored, early serial number Beomaster 8000 09 Microcomputer module in this Beomaster 8000 receiver.  I re-installed the original unit's metal shielding box on the replacement 09 PCB.

After working with this early serial number Microcomputer PCB, although the shielding box is a pain to work with, I should have removed it by focusing my de-soldering work on just the tabs that were soldering onto the shield box lids.

Reinstalling the box is much easier than removing it.

Here is a picture of the new Microcomputer PCB at the corner where the original board had broken traces.
Everything is good with this 09 module.

Here is the new Microcomputer board reinstalled in the Beomaster 8000 cabinet.

I went through all of the control panel functions both with the control panel buttons and the remote control buttons.

Everything worked as it should except that the FM station display has the two missing LEDs.

I can deal with the display LEDs later.

Right now I wanted to try out this Beomaster 8000 and see how it sounds.

Before doing that though, I needed to check the No-Load Current and DC Offset of the Beomaster 8000 Output Amplifier boards per the service manual.

Both the No-Load Current and DC Offset values needed adjusting.  

Here is the No-Load Current check after I adjusted the TR226 trimmer on both channels.

Note: These checks and adjustments are made with no speakers connected and the volume at zero.

No-Load Current

DC Offset

Those service manual adjustments encountered no problems so I moved on to some real listening tests.

I connected up an FM antenna and an iPod Nano to Tape 1.
I connected a pair of Beovox MC 120.2 speakers to Speaker 1 outputs of the Beomaster.

I will leave the Beomaster 8000 playing for several hours with the volume level at a low volume level (2.4).

Beomaster 8000 Type 1903 - Arizona Restoration Project - Microcomputer Board

Having determined the Microcomputer PCB (Module 09) has a problem in this Beomaster 8000 receiver, I removed it to examine it more closely.

I am not fond of these Microcomputer (uC) PCB modules from the early serial number Beomaster 8000 units.

B&O decided to solder the top and bottom (metal) lids of the uC assembly to the PCB. On later serial numbers, B&O changed the PCB shielding to be a metal frame around the PCB with snap-on lids.

To remove the metal lids on this uC PCB, the board connections have to be de-soldered.
It is safest here to use solder wick on the six mounting spots.

Here is the 09 PCB with the metal lids removed.

Right away I could see some breaks in the 09 PCB traces near connectors P75 and P76.

I verified the open trace connections with my DMM then set about repairing them.
Of course I hoped this would be the single source of the 09 Module problems and could move forward.

Here is the PCB 09 with the breaks in the traces bridged.  On the wider traces I decided to use some copper strips.  On the two thin traces I just used some signal wire.

Note that while I had the 09 PCB on the soldering station, I reflowed the solder joints on all of the 09 PCB connectors.

I tested the connections again with my DMM, then re-installed the 09 PCB in the Beomaster to try powering it on again.

This time I do get the Standby LED with this original 09 PCB.

The control panel buttons do not consistently operate the Beomaster 8000 though.
I double-checked source selection, volume control and FM tuning using a Beomaster 8000 remote control.

That worked so there is an issue with the control panel buttons connected to this original 09 PCB.

With the remote control though, I checked out some of the Beomaster 8000 functions.

I could select all of the sources but the FM tuning did not work.  The lack of FM tuning was a reason the owner sent me the Beomaster 8000 so at least the reason for that problem makes sense.

This picture shows the selection of FM presets P1 and P8.  You can see that the FM tuning indicator is not correct.  The tuning control couldn't do anything that made sense on the display either.

This photo shows source selections for phono and tape 1.  I also checked tape 2.  Those all select fine except that I had to do the selections from the remote control.

My next test was to uninstall this original 09 PCB and replace it with one of my Workshop Beomaster 8000 09 PCB modules again.  This time, however, I grabbed my Workshop 09 PCB from an early serial number Beomaster 8000.  That is a better match than the late serial number 09 PCB I tested with earlier.

Here is my Workshop 09 PCB next to the fault 09 PCB from this Beomaster unit.

They look identical except that my Workshop 09 PCB has a new 22uF capacitor and 1uF capacitor.
It also has new oscillators.

With my Workshop 09 PCB installed, the Beomaster 8000 source selections, volume adjustment, balance adjustment and FM tuning all work.  Both from the control panel and the remote control.

I can see that a separate issue with this Beomaster 8000 is on the display segments. 
The FM tuning display is missing one segment and the period for the frequency display.

What I have to do next is figure out what the solution will be for this Beomaster 8000 unit.

This project has budget and time constraints that limit my choices.

That leads me to wanting to just replace the original 09 PCB with my, already restored and working, Workshop 09 PCB.

The time it would take to troubleshoot and rework the broken 09 PCB could be expensive and at the end, it would still be a PCB that had repairs to some broken traces.  I could live with that if this were my own Beomaster 8000 but not when it is a unit that has to be shipped back to an owner.

Another option would be to assemble a new 09 PCB from scratch using a new PCB from Fredrick Adenholm.  He has reproduced the Beomaster 8000 Output Amplifier PCB, Display PCB and uC PCB.

I have all three of those blank, ready to populate boards.  The 09 PCB is pictured above.

However, in the case of this project, doing that to replace the 09 PCB is out of scope.

Beomaster 8000 Type 1903 - Arizona Restoration Project - Power On Troubleshooting

After the initial assessment of the first post on this Beomaster 8000 (Type 1903) restoration, I left off needing to know if this Beomaster unit had a working power supply.

The expected "standby" LED segment (a red dot) was not illuminating on the display so I checked the power supply for the 5 volts the Beomaster 8000 Microcomputer PCB needs to operate.

The incoming DC voltage (about 11 VDC) was present on the reservoir capacitor and the regulator measures a 5 V output.

I didn't check the ±15 volt regulators but I did measure their reservoir capacitors.  They measured as expected.

After double-checking the cables and individual wires from the power supply to the Microcomputer PCB, I tested the Beomaster 8000 power on again.

Same result, the Beomaster 8000 appears dead.

The problem is most likely in the Microcomputer PCB.

One reason I have a Workshop Beomaster 8000 unit is so I have easy access to known good boards from a working Beomaster 8000.

I swapped the Microcomputer PCBs between this restoration unit and my Workshop Beomaster 8000.

The result is the Beomaster 8000 comes to life.

The source selection functions all operate as well as the volume dial and tuning dial.
There are some display segments out but I will sort those later.

The owner of this Beomaster 8000 says that he stopped using the receiver because the FM tuning stopped working.  Since it appears to work with my "good" Workshop Beomaster 8000 Microcomputer PCB, I can say that the Microcomputer PBC of this Beomaster being restored has a problem.

I will start in on that PCB next.

Beomaster 8000 Type 1903 - Arizona Restoration Project - First Look

I have been waiting for a while now to clear out other restoration projects so I could return to some Beomaster 8000 restorations.

The first one is a very nice, one owner Beomaster 8000 from Arizona.

The two, round control wheels operate smoothly and cosmetically, everything looks great on this Beomaster.

I plugged the Beomaster in but no "standby" red dot appeared on the display.

On to looking inside...

The center control bar on the Beomaster 8000 slides to the left in order to unlock the cabinet and access the screws hold the bottom control panel in place.

After removing the control bar, I could see that this Beomaster 8000 has been worked on in the past.
One tell is that two of the three, flat, metal springs for the control bar are missing.
Those springs just lay in place under the control bar and easily fall out when the Beomaster 8000 is opened up for service.  Unfortunately it is more common than not to open up a Beomaster 8000 and discover missing control bar springs.  I guess people lose the springs or forget to put them back.

Here is a photo comparing this unit with one that has the control bar springs.

I will have to see if I can fabricate some spares.

Another issue I quickly discovered was that the metal lid for the filter control panel did not open and close properly.

That lid is supposed to be spring loaded so that it slowly raises by itself with the control bar is pressed.
In this case, the lid has to be lifted manually and it free-falls shut.
That problem is also common though, most likely a broken lid lever.

This Beomaster 8000 unit has the original B&O configuration of the audio input sockets.
The tape RCA input and output jacks are on the TAPE 1 source.  Later, after serial number 2554003, those changed from the TAPE 1 source to the TAPE 2 source.

I lifted the front control panel into the service position next.

That confirmed that this is an early serial number Beomaster 8000.  At least, prior to B&O changing the Microcomputer Board.  This unit has the type of Microcomputer Board where the metal shielding case is soldered closed.  Later serial number units changed to a metal shielding case that snaps together.

I believe that began with serial number 2375027.

Here is a photo of the Microcomputer and Display boards.

Those boards appear to be original and untouched.

To the left side of the cabinet are the Preamplifier, FM, Filter and Left Channel Output boards.

The capacitors on the Preamplifier and FM boards look to all be original.  The Left Channel Output board looks like it has had some electrolytic capacitors replaced before.

I can also see the metal door lid mechanism now.  It does have a broken lever.
The lever can be replaced.

Behind the Microcomputer and Display boards is the Beomaster 8000 power supply and the Right Channel Output board.

The capacitors on those boards have been replaced already.

My next step will be to get out some test leads and trouble-shoot the power problem to see why the Beomaster 8000 standby LED is not coming on.

I will cover that in the next post.