Beomaster 2400: Replacing the audio input panel

The last post on this Beomaster 2400 showed that it had a broken mount for the audio input source panel.

I was able to find a good replacement panel from another Beomaster 2400 I had purchased for my own use. It also has the 7-Pin DIN jack for the Phono input I need because this Beomaster 2400 will be connected to a Beogram 4004 and we want the remote control functionality between the two.

No worries on the Beomaster I am stealing this part from. I will actually just trade connector panels and figure out a repair solution with pieces from Beolover's DIN panel repair kit for the Beomaster 8000.

Here is the diagram of the Beomaster 2400 DIN source panel from the B&O upgrade kit to add Phono DIN connector pins 6 and 7 for remote control capability of the Beogram 4004.

Here are front and rear photos of the new input source panel. Its mounting tabs are intact and I have added text to the photos to show the pin numbers and function to match the B&O diagram.

Now to begin soldering the Tape and Phono wires to the new DIN jacks.

I removed all of the Beomaster 2400 control panels yet again to work on this audio source DIN connector panel. Here are the wires connected to the new DIN panel.

...back in business again...

Beomaster 2400: Dealing with a broken audio connector

While connecting up audio sources to test this newly restored Beomaster 2400 I discovered the audio source connection panel is broken. I didn't notice it earlier so it must have been barely hanging on. When I started to use it the weak plastic tab holding it in place finally gave way on one side.

As you can see in the photo the loose connector panel can pull away. It still works but no longer stays in place.

Here is more detail on what the broken DIN connector mounting assembly looks like.

The DIN Phono connector on the Beomaster 8000 can fail in a similar fashion.  Beolover makes a 3D printed repair kit for it but this one is a dual DIN panel.  I might be able to still use part of the kit but I think it will be better in this case to just replace the dual DIN jack panel with another one that is still intact. In the next post I will change this connector panel out and then I can get on with the Beomaster 2400 testing.

Beomaster 2400: Reassembly and First Play

The Beomaster 2400 lamps all function. The power supplies are good and the no-load current adjustment is complete.

Note that the phono jack on this Beomaster 2400 is the 7-pin DIN type plug. It supports the Beogram 4004 remote control connections.

This Beomaster 2400 had a couple of shoddy left and right cabinet trim pieces. I found a couple of good ones, did some light sanding and applied some boiled linseed oil.

Before I attach the tone controls and FM tuning panel and before I attach the bottom plate there are a couple of service manual adjustments I need to complete. There is an FM1 tuning voltage adjustment and an FM5 tuning voltage adjustment. In both procedures a trimmer is adjusted while monitoring the DC voltage at 4TP1. The measured voltage level in both adjustments should be 4.7VDC with the tuner at the 88MHz stop.

When I attached the Beomaster 2400 bottom plate I also had to replace the four plastic feet. All of the Beomaster 1900 and 2400 units I have encountered so far all have deteriorated (or missing) cabinet feet. Fortunately Martin Olsen can source these.

Now for a quick play test. I connected an iPod Nano to the Tape 1 DIN input and my FM antenna cable to the Beomaster 2400 antenna jack. I am currently out of functioning Beogram 4004 turntables so I will have to wait to test that.

As you can see from the photos I also checked out the Beomaster 2400 remote control. The receiver works and sounds great.

I will let it run for a while to burn it in before I hook up my dummy load resistors to run some performance checks.

This is the fun part.

Beomaster 2400: Power Supply Checks and No-Load Current Adjustment

The lamps are now all replaced and tested.  I am ready to move on to the power supply checks.

First however, I installed the Beomaster 2400 control panel and rechecked the operation of the touch buttons and lamps. This panel is sometimes tricky to install as there is a spring contact for each of the touch control buttons.  Those must all align properly to their metal posts.

Here are photos of those checks. Note that the color of the indicator lamps isn't accurate to how they actually appear in person. It is always difficult to capture lighting pictures and still have enough light to see the audio component in the photo.

...and finally...Standby

Now for the voltage checks.

First is the +15VDC power.  Here is the +15V supply reservoir capacitor. 22V at the reservoir capacitor is a good value. Next is to adjust the output of the +15VDC regulator.

The service manual says to use the 2R151 trimmer to set the +15VDC supply to +15.0V making the measurement at 2TP15.

No problems adjusting that. Now to measure the Beomaster 2400 ±31VDC supplies. I measured those voltages at the two large 5000uF reservoir capacitors (0C7 and 0C8).

I have a couple of wires connected to the test points for the Beomaster 2400 no-load current adjustments.  The space is too cramped to easily attach measurement probes across the emitter resistors (2R256 and 2R356) for this adjustment so I like to temporarily solder some test wires for the no-load adjustment. Both channels easily dialed in to the service manual stated 12mA with the multi-turn trimmers I installed earlier.

Everything tested good so I can finish up the re-assembly of this Beomaster 2400 unit.

Beomaster 2400: Indicator Lamp Checks

Now the project gets to the fun part...reassembly and testing.

First thing is to put all of the parts I removed back and turn the Beomaster 2400 on.

I want to see if the replaced lamps all work and I will want to measure the Beomaster power supplies.

This post will show the testing of the new lamps.  The volume level indicator lamp module and the Bass/Treble/Balance module have to be re-soldered in place first. 

Here is the volume level lamp module reinstalled.

...and here is the Bass/Treble/Balance lamp module.

With the Beomaster powered on these two lamp modules illuminate.  

The source and FM tuning indicator module has two connectors so no soldering is required to reinstall it.

The lamps on this module all worked except one, the FM3 source selection lamp.
It turned out that I had the LED replacement lamp installed with reverse polarity.  I switched it around and then it too worked.

I was curious as to how I got the polarity wrong on the FM3 source indicator board. I used the previous Beomaster 2400 restoration project as a reference so the polarity should have been correct.
Looking at the previous project I now see that this indicator lamp panel has differences more than just the two board connectors.

Here is the Beomaster 2400 Type 2902 indicator board from my previous restoration project. The FM3 lamp (between the two board connectors) does not have the jumper that the current Beomaster 2400 does.  The same is true for the Beomaster 1900 Type 2903. The wiring path for that lamp is indeed different...as I found out.

On to the power supply and no-load current adjustments.

Beomaster 2400: Lamp Replacements

This post shows my Beomaster 1900/2400 lamp replacement method.

I replace the two volume level indicator lamps with new incandescent type lamps. These lamps are part of the the volume level circuit and need the lamps to be the incandescent type of lamp.

This is the board with the original lamps.

Here is the board with two new incandescent lamps installed.  I source them from Martin Olsen.

Next is the update to the Beomaster 2400 source selection and FM indicator lamps.
Again, here is the original lamp board for the source selection and FM indicator lamps.
I marked the positive side on the lamps I will be replacing with LED type bulbs.

First is the replacement of the three incandescent bulbs for (FM Stereo indication and FM tuning).

Next are the replacement of the source selection indicator lamps with LED modules.
These are a bunch of my homemade LED assemblies. The single ones are for the Beomaster 1900/2400 source indicator lamps. The dual LED assemblies are for the Bass, Treble and Balance position indicators.

Last are the replacement of the incandescent lamps for the Bass, Treble and Balance indicators.
Here is a picture of the board with the original incandescent lamps.

I always change these lamps to LED type lamps.  I often find that the plastic position indicator masks that fit over these lamps are damaged due to heat from the lamps. The LED replacements operate at a much lower temperature so should be better for the long term and are not damaging to the plastic indicator masks.

In the next post I will reassemble the Beomaster 2400 next and check the results of the restoration work so far.