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Beogram 4002: Restoration of DC Motor Video Published - Check It Out!

By popular request (really, I got quite a few emails about this!...;-), I finally completed my Beogram DC motor restoration video! It demon...

Friday, January 17, 2020

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...
















Wednesday, January 15, 2020

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.

Friday, January 10, 2020

Beogram 8000: Test Drive with Miles Davis

After performing the mechanical and electronic adjustments of the Beogram 8000 that gave me some fun insight into aging transistors recently when I troubleshooted its record detection circuit, it was time to reassemble the unit and do a test drive:
I selected "Water Babies" by Miles Davis. One of my favorite records of all time. In fact I bought this one in 1979 as my 29th record (as you can see from the number label in the top left corner...;-)! This Beogram 8000 came with a decent MMC20CL cartridge and Miles sounded very smooth! It seems this Beogram is working well again. I will play it for a few more days and then it will be time to send it home to California.

Sunday, January 5, 2020

Beogram CD X: Revisiting To Address Some Loose Ends

I finished up the Beogram CD X in a previous post. It has been playing in my workshop since then. I haven't encountered any issues with actual CD play. However, while playing around with the CD X controls I did discover that the seven segment display window has a broken segment.

Pressing the "Display" text on the CD X touch panel will cycle the display from displaying the current track time, total elapsed time and the track number:number of repeats.

While in those other display modes I could see a missing segment.





















The Beogram CD X seven segment display is a module specifically made for several CD players of the CD X generation. I contacted Martin Olsen to see if he had any spares. Luckily for me he had a New Old Stock (NOS) module he could source me.

Having recently received it I opened the CD X back up for replacement of the display.































Re-installation of the CD X circuit board with this display is not as easy as it appears. While there are just three screws to mount the circuit board to the CD X frame...it must be aligned just right. The glass touch panel has a number of small rubber contact tabs that must contact metal posts on the board. If they don't make correct contact the touch panel won't operate correctly. It took me a couple of tries to get the CD X display board re-installed/re-aligned where everything worked again.

Once I got past that re-assembly hurdle the CD X was back to full functionality again.





















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.

Wednesday, January 1, 2020

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.