Beomaster 4400 Type 2419: Reassembly and testing again (UPDATED)

I am pretty sure this has been one of the most difficult Bang & Olufsen restorations I have encountered.  Cleaning, recapping and adjusting a Beomaster 4400 receiver is not usually this difficult. The reason for that is I never had to dive in and disassemble the front panel. Unfortunately the power on/off switch on this one made it necessary for this project.

One big lesson I am taking from this project does involve the front panel and all of its related components. I started on the front panel by removing the minimal amount of things to get to the switch. That sounded good at the time but in hindsight the better approach (and the one I will use from now on) is to bite the bullet and disassemble everything from the front panel. Unobstructed access to the parts are the most important thing.

Had I done that from the outset I probably wouldn't have run into this situation...

It was time to re-install the rebuilt power on/off switch to the Beomaster 4400 switching rail.
The mounting tabs for the switch on the original switching rail were all but gone.
The tab on an unused switch mount is shown in the green circle. That is what the tab should look like.

I gave it a go anyway to see what it would take to mount the switch on the original switch panel.
NOT SO GOOD.  Obviously this is not Beolovely and unacceptable.

I had another switching rail from a spare parts Beomaster 4400 that the replacement power on/off switch came out of.  It still had serviceable mounting tabs.

Here is what I mean about complete disassembly of the front panel.
The switch panel assembly is removed in the photo above but for full access and working room in remounting the power on/off switch, the circuit board (and flexible circuit assemblies) should be removed.

With the switch remounted I reinstalled the circuit board (PCB6). Note that in the photo below I also desoldered the flexible circuit from the FM preset assembly.  This is important to do because the preset assembly is bulky and heavy. Leaving it attached makes it very risky to cause the flex circuit to crack and break. I have seen cases of that. So play it safe and just desolder the flex circuit from the preset assembly.

While PCB6 and the flex circuit were separated I took the opportunity to replace the 6R1 2.5KΩ trimmer. If the trimmer needed to be replaced later I would have to completely disassemble all of this again and I really want to avoid that. So to be safe I replaced it with a new Bourns trimmer.

Another thing to take care of for future insurance is the small, red FM Stereo indicator lamp. It is an LED that has been glued to the Beomaster 4400 front panel.

I investigated removing it but I couldn't figure out how without breaking the LED.

So I reconnected wires to the lamp with a small, two-pin connector for ease in removing the front panel. I also tested the LED.

That appeared to work but when working on the front panel reassembly one of the LED wires broke off again.

I reworked the wire attachments to be more secure and used a dab of epoxy on each wire to fix it to the panel as a strain relief for the leads to the LED.

In the process I didn't notice that I got the wire colors reversed where they attach to the LED. Luckily I have the 2-pin connector I had added earlier so I can just take care of the polarity there.

Continuing on with the front panel reassembly I reconnected the components.
I didn't break out the individual steps in photos (sorry) but I did find that mounting the switch rail to the toggle switch actuators and front panel is really, really difficult to do if the actuator assembly is already attached to the front panel.

I was successful by first attaching the actuator assembly to the switching rail. This allowed me to properly set the position of the actuators.

After that mini-assembly I was able to fit the switching rail with the actuators pretty easily into the front panel.

Next up was the task of resoldering all of the wires I had to remove as part of the disassembly.

Here are a couple of photos of the reattachment of the flexible circuit to the FM Preset assembly and the remounting of the main FM tuning dial.

Finally the new power on/off switch can be hooked up to the Beomaster 4400 and I could try another power test.

I applied power with my variac and dim bulb tester in the circuit for safety.
The first thing I checked was the +15 VDC regulator as that was part of the earlier repair where there were burned up ground traces on PCB5.
I also still have the FM boards removed from the Beomaster. Because they were involved with the burned ground traces I need to check them out separately before putting them back into this Beomaster.

Another quick check was made on the idle current for both channels in the output amplifiers.  They did require some adjustment so I performed those and the Beomaster 4400 was ready for a listening test.

Like before I used a pair of headphones and an iPod Nano connected to the Tape 1 input.

Success finally.  The new power switch operates perfectly and I have nice music playing through the Tape 1 source.

With this Beomaster 4400 unit though, it would not be in character for everything to work perfectly.

A new issue has popped up. I had to use the Linear switch to get sound in both channels. With the Linear switch deselected the left channel drops out.

The Linear switch is an option to bypass the Treble and Bass tone control section of the Beomaster 4400 preamp. So either the left channel is not making it through the tone controls or there is a problem with the Linear switch.

I was hoping it is just a wire that isn't mating well (maybe broke off during the front panel reassembly)

Sure enough, a broken wire to the switch.

I resoldered the broken wire and now the normal stereo selection works.

Now that problem is solved and I can return to the FM boards on this unit.