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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...

Sunday, July 22, 2018

Beomaster 4400 (2419): Reassembly and Power Checks

Today I reassembled the electrical components of the Beomaster 4400 and performed the all important first power on test. The goal here was to verify all of the board component work is correct and the Beomaster can be plugged in, turned on and all of the power supply voltages are good.

I installed the FM boards (PC1, PC2 and PC3) first.
























I had removed the shield cover to the main power switch so I reinstalled those parts now.






















The last board to install is the PC4 preamplifier board.























As I was tightening the mounting screws of the preamplifier board to the cabinet I was reminded of a problem (in my opinion) with the design of the connector panel. The RCA jacks are too close together. This is also the case on the Beomaster 4000 receiver. I don't own any audio cables with RCA plugs that can mate with the Beomaster 4000 and 4400 receivers. The only solution will be to make my own and use heat shrink tubing instead of the outer shell that comes with the RCA plugs.






































You can see that only the bare RCA plugs can fit the space allotted by the Beomaster connector panel.

I always connect Bang & Olufsen source components to the Beomasters so it isn't a problem for me but it is something to be aware of if you are planning on using your Beomaster 4400 for some non-B&O audio source components. The solution in that case is to get an adapter cable that goes from the RCA plugs to a 5-pin DIN plug.

Anyway, just a pet peeve on my part. Continuing on it is time to see what happens when power is applied to this newly recapped Beomaster 4400.  In the case of the older Beomaster amplifiers I like to use a variac with a dim-bulb tester on the first power up. It is just added protection in case I missed something. 






































The Beomaster 4400 powered up fine. That is great so now I checked all of the DC voltages in the Beomaster.

Here is the +15 VDC power check where the regulator 0IC1 attaches to the PC5 board.






















Next is the +35 VDC rail voltage at TP3 of PC5.

























Then the -35 VDC rail voltage at 5R16 of the PC5 board.






















I checked the +24 VDC voltages at the emitters of 5TR3 and 5TR4.  Here is a picture of the 5TR3 emitter. Both measured +24 VDC as they should.






















Last I checked the -12 VDC at TP15 of PC5.


















Very nice. Everything looks good so far. Tomorrow I will start adjusting the no-load current (idle current) and the source levels. Once that is done I will be able to see how this amplifier performs with audio signals.

Thursday, July 19, 2018

Beomaster 4400 (2419): Reservoir Capacitor Replacement and Transistors Remounted

Last night I installed the two new 0C8 & 0C9 10KuF reservoir capacitors. These are the capacitors for the Beomaster ±35V rail voltages.

The replacement capacitors are a little smaller in diameter and length but I found some 105°C Nichicon capacitors that still fit into the Beomaster 4400 mounting bracket.

I reattached the ±35V rail voltage wires using some small terminals.






















I added some heat shrink tubing for some added protection.






















Here is the completed reinstallation of the reservoir capacitors.






















Now I was able to resecure the main (PC5) board in the cabinet. I am using SilPads for the insulators and thermal exchange between the power transistors and the heat sinks.




































































This Beomaster is now ready for the reinstallation of the small boards.




Sunday, July 15, 2018

Beomaster 4400 (2419): PC5 Recap

Today I tackled the large PC5 board. The service manual titles it the AF Amplifier, Power Supply, Muting and Silent Tuning board. I'll often refer to it as the PC5 board, main board or output amplifier board.

The PC5 board has the most electrolytic capacitors to replace and it has six trimmer resistors.

Here is a picture of the board before recapping.

Beomaster top opened up


















Boards and reservoir capacitors removed






















Since this board is the largest and kind of difficult to remove for recapping I will take the opportunity to measure the output transistors (the ones mounted to the heatsink). I will also check and reflow solder joints on the board to board wires and the output amplifier transistors.

The transistors measured good but there were a couple of bad solder joints where the transistors attach to the PC5 board.

The recapping of this board takes a while as it has quite a few capacitors. There are a lot of 1uF, 2.2uF and 4.7uF capacitors. I think this particular Beomaster may have set a new personal record for the number of out of tolerance capacitors found. I found 1uF capacitors measuring as high as 4uF.

Here is the recapped PC5 board.























Tomorrow I will install the new reservoir capacitors and this Beomaster will be about ready to try out.

Saturday, July 14, 2018

Beomaster 4400 (2419): Recap Review Leads to Preamp Rework

A nice side benefit of documenting these Bang & Olufsen restorations is that it forces me to review and double-check my work. Several times I have thought a task was complete only to look at the photos of the work and spot a problem.

In the case of this Beomaster 4400 I started thinking about the next few steps of the restoration and when looking at the preamplifier (PC4) board I realized that I had made the source input level adjustments more difficult in the way I installed the trimmers.

The original trimmers are designed for top and bottom adjustment. That is nice but I wanted to replace those single turn, open type trimmers with some Bourns multi-turn, sealed trimmers. The new trimmers only adjust from the top.

Here is a photo of the Beomaster 4400 preamplifier as I received it.






















Most of the time these Beomaster receivers still have the seals over the input level trimmers as people leave them per the factory settings. If they need adjustment the paper seal can be broken and the trimmer adjusted from underneath the Beomaster.

In my initial PC4 - preamplifier board recap I oriented the multi-turn trimmers as you normally would on the component side of a board.





















Unfortunately that would mean making the adjustments before fully installing the Beomaster 4400 preamplifier board.

Like we do on the Beogram 400x RPM trimmers, I flipped the input level, 50KΩ trimmer resistors over so they adjust from the trace side of the PC4 board.
























That is much more practical. The owner can then tweak the input levels without opening up the receiver.

Thursday, July 12, 2018

Beomaster 4400 (2419): Into the Recap

These seventies era Beomaster receivers have a low profile and are quite a challenge to open up into a service position. I like the way the eighties era Beomaster units were designed with some consideration for the service technicians. Oh well, it is what it is. The Beomaster 4400 is an improvement over the Beomaster 4000. There are some board connectors.

Here is the Beomaster opened up and ready for recapping.






















The PC5 board has the most recapping work and does not unplug completely for removal. I disconnected enough wires to it so I can get to where I need to with regards to replacing capacitors but I will tackle the PC5 board after I recap the smaller boards.

I started with the PC3 - Stereo Decoder and Indicator Circuit board. It is a good one to warm up on.


Here is the recapped board. For now I am leaving the trimmer resistors as they are on the FM boards. I will replace them as necessary during the Beomaster performance testing. 





















Next are the PC1 and PC2 FM boards. There are just three capacitors to replace between them.


















...and here are those boards after the recap.























Now for the PC4 - Preamplifier board.





















On this board I also changed out the six 50KΩ trimmer resistors as I recapped the board.





















Tomorrow I will tackle the large, PC5 board and the two reservoir capacitors.

Friday, July 6, 2018

Beomaster 4400 (2419): New Beomaster Project From Canada

With the Beogram 4002 (5513) project moving into its listening test phase I can put a new project on the workbench. I have been looking forward to this next one as it is a very nice late 70's era Beomaster 4400. This unit comes from a friend up in Canada so it has travelled quite a ways to get here.

When it first arrived I had to see how it looked in a recent Bang & Olufsen MC40 cabinet I acquired.






















Looks like a great fit :-)

Now on to the workbench...























Very nice. This Beomaster has been well taken care of.

The task on this receiver will be to replace the old electrolytic capacitors and some of the trimmer resisters. Then I will see what the state of it is.

Thursday, July 5, 2018

Beogram 4002 (5513): First Record Play Testing

Finally....time to see how this restored Beogram 4002 (5513) turntable does playing a record for listening pleasure.

First though, a couple of pictures showing some tidying up of some loose ends. In the last post I neglected to post the pictures of installing new cabinet guides and the rework of the phono cable.
So before showing the first record play photos here are a couple of pictures showing the Beolover Beogram 4002 3D cabinet guide parts.























There are five total cabinet guides. The last photo shows the lone black one that is used for the front center of the cabinet so it isn't noticeable. Note that these are not washers. The cabinet guides hold the plinth in place but allow it to slide forward and backwards for opening up the Beogram cabinet. The early Beogram 400x turntable guides were made out of a brittle plastic that almost always broke. In the later model Beogram 400x turntables B&O switched to a metal guide to fix the problem. The Type 5513 Beogram 4002 was before the metal guide came out. Even though they are just a small part they make a big difference. A lot of people will just substitute flat washers but they don't provide the function needed.

Now the phono cable. The original DIN plug cable had already been replaced and while the replacement was a nice cable I didn't like the way the wires terminated in the P9 plug to the Beogram phono output board.
































I removed each P9 pin and reworked the wire connections. The wires connected to pins 2 and 4 are not used so I removed them.






















Here is the reworked cable plugged into the Beogram phono output board. I reused the blue wire and its P9 connector for the left and right channel shield wires. The small switch we install allows the option to short the shield wires to the chassis ground wire or leave it open.























That is a lot cleaner looking. I can live with that.

Time for some lively Jazz from Buddy Rich.























I have used those for Beogram play tests before and keep using them for some reason :-).

Next the Beogram will go through a day of testing like this while I make sure the set down positions are good, the phono muting delay is satisfactory and there are no tracking problems. Once those things are satisfied I will install the remaining cabinet pieces and go through a week of listening tests before this Beogram's owner picks it up.

Thanks to Beolover by the way for another excellent job on parts and the platter motor restoration.