Beogram 4002: Final Tasks, Adjustments & Playing Records

It is time to finish up this Beogram 4002 Type 5513 project. As a continuation of the corrosion damage repair I am replacing the 5-pin DIN phono plug.

Here is a nice reference diagram Beolover created a while back that shows the audio path from the MMC cartridge connector to the 5-pin DIN plug.

I like this diagram because when I am replacing the phono cable plug this shows the phono signals I check continuity on from the Beogram output board connector (P9) to the front of the plug.

Here is a picture of a continuity check for the phono right channel from the phono DIN plug to the output board P9 connector.

I installed a REAN 5-pin DIN replacement plug that has gold contact pins.

A note to other DIY folks that do this - Some of these Beogram phono cables have a cable diameter that makes installing the REAN rubber boot extremely difficult. The fit is really, really tight.

Another phono signal related change I made was to return to the output board and install a grounding switch between pins 5 and 6 of the P9 connector. That is signal ground and shield ground respectively. The Beogram 4002 units come with a separate grounding wire so owners can connect their Beogram chassis ground to an amplifier's chassis ground should there be hum in the signal path.
This grounding switch eliminates the need for that extra grounding wire as the switch can be flipped to short the two grounds together in the Beogram if needed. A nice option and the switch is easy to get to.

One last electrical task is to install the two RPM indicator light replacements (33 & 45 RPM lights). This upgrade of incandescent lamps to the Beolover LED replacement is not for cosmetic reasons. Beolover's ongoing testing of Beogram 4002/4004 DC platter motor stability has shown a positive measurable effect of the LED lamp assemblies over the incandescent lamps. So we recommend them on all of our Beogram 400x restorations.

One weak part of the Beogram 4002 design are the mounting clips for the RPM indicator panel into the control panel. The mounting clips are a hard plastic that often becomes brittle over time and cracks. This unit had a couple of hairline cracks so I applied some preventative patches.

I started the final reassembly of this Beogram unit which includes the service manual adjustments.

The first adjustment is for the Beogram platter height so that the distance from the top of the fixed arm (and tonearm) is 23mm from the surface of the platter. That adjustment is made using the large nut on the platter hub.

The tonearm lowering limit and pickup arm length adjustments are next.

That is followed by vertical and horizontal arm parallelism.

While the platter belt is still removed I adjusted the tangential arm sensor.

Now for the deck panels and the platter position adjustments.

Everything looks good. I performed the arm balancing adjustments earlier so the final adjustments are for the platter speed trim pots.

This Beogram is cleared for record play. I'll give it a listen as I document this blog post :-).

It looks like this Beogram is ready to go back home to Houston. Now where's my copy of "Houston El Mover"?

Beogram 4002: New Project From Houston

I get to switch gears from Beomaster restorations back to a Beogram project next. I love working on both so either way it is a treat for me. A gentleman from Houston brought me a couple of Beogram 4002 Type 5513 turntables he had acquired some years ago. Eventually they began to age and stop functioning correctly.  Like most Beogram 4002 owners he found that he missed playing vinyl records on them so he had to get them restored.  I am lucky enough to receive the task and look forward to getting these back 100% working again.

One at a time though.

These were functioning well for the owner not too long ago so the Beograms are in decent shape. Here is the first Beogram turntable opened up.

I already removed the DC platter motors back in March and sent them to Beolover for a full restoration. I have those motors back and they have been waiting for the rest of the Beogram restoration to catch up.

There are a few areas inside this Beogram where rust is starting to look bad. I will clean those up and put a stop to the rust. 

The Beogram phono DIN plug is badly corroded as well and the best solution there is to replace it.

Here are a couple of pictures of some of the chassis components that have rust.

Interestingly this Beogram 4002 is one of the rare few I have seen where the plastic transport bushings around the floating suspension locking screw are still intact. They are still soft and in good shape. Most of the units I see have brittle bushings that have cracked and are in a million little pieces scattered throughout the Beogram. I will treat the bushings with some plastic restoration fluid that will keep them from drying out.

The main circuit board looks in great shape. No signs of heat stress or corrosion there.

The tangential arm assembly also looks to be in good condition. 

Recapping the main board, replacing relays and speed trimmers along with cleaning and adjusting the tonearm mechanics should get this turntable back to working the way it was designed. The restored platter motor along with the replacement of the trimmers and speed indicator lamps (with Beolover's LED replacement modules) will have this Beogram spinning vinyl better than ever.

Time to get to work.

Beogram 8000: Final Steps

I was kind of lucky I suppose in finding the intermittent pause culprit on the first suspect. However it was the most likely when reviewing the problem. Even though the behavior was intermittent it lined up with a problem Beolover had on a Beogram 8002 project earlier. After replacing the Beogram 8000 original control panel board with one of my spares -

the result has been over twenty error-free record plays.

Returning to the original control panel board to look at repair options I examined the LDR (photoresistor) devices for the forward and reverse controls.

Visually examining them and testing their resistance with different light sources didn't reveal any problems. These devices can become unreliable over time and exhibit the intermittent behavior I experienced so I decided to apply the repair Beolover did on the Beogram 8002.

I ordered the same LED from Newark and some GL5549 LDR devices from a couple of different sources. Replacing the original lamp with an LED requires a load resistor so I used the 1K ohm value Beolover had set his to.

Using the same parts I was hoping the fix would just be a quick install, test and go operation. Unfortunately I found that these GL5549 LDR devices vary in performance by quite a bit. It took quite a while to find a pair of these new LDRs to match and be around 20K ohms when in place on the board.

After finally finding a couple of acceptable LDR devices to try I mounted them with some temporary glue to secure them in their respective mounting slots.

I prepared the control panel board for re-installing into the Beogram. That included adding my little LDR test connector. This time I used 30 gage hook-up wire so the test connector can be left in the control panel. I matched the wire colors to what the Beogram 8000 colors are for the LDR measurements. That makes it easier to remember later if I have to retest the LDR voltages.

The connector is also a female connector so I don't have to worry about anything shorting by it when I leave it in the Beogram.

Testing the reworked control panel board with the new LDRs was interesting. I ended up having to re-adjust the position of one of the LDR devices. That is why I use glue that isn't permanent. Eventually I was able to get the forward and reverse LDRs adjusted within the 600mV - 700mV range necessary for successful operation. The service manual originally asked for 620mV but later updated that value to 650mV. I talked to another Bang & Olufsen technician who told me a solid value between 600mV and 700mV is sufficient.

As you can see in the picture above, the adjustment for a working forward and reverse operation resulted, again, in quite an imbalance in the adjustment screws of the control panel board. The voltages are stable though so I am going to run another play test with this board just to see what happens.

For this project though I am inclined to go with the replacement control panel board that I ran the twenty successful record plays with. The forward and reverse LDR controls are closely matched on that board and I feel will be more of a sure thing. This replacement repair is looking good but I will feel better about it if I can do a long term test with it.

There is one more issue that cropped up during the play testing of this Beogram 8000. Another intermittent problem but one that was easily recognized. A couple of times after a record completed play I noticed that the phono mute did not occur. That means the Beogram phono mute relay is acting up. This picture shows where the muting relay is located. It is easy to get to but does require opening up the Beogram case again. Oh well.

I hadn't planned on replacing this relay but since it has come up I asked the owner if he would like the phono grounding switch to be added. This is a convenience option that Beolover has been doing on Beogram 400x and 800x turntables. The added switch gives a user the option of setting the turntable up as it is originally or shorting the phono signal ground to the Beogram chassis ground.

This is a nice feature for Beogram owners that use the turntable with a non-B&O amplifier. I pair a lot of my Beogram units with my Yamaha C2a, C2x and C-70 preamplifiers. Those pre-amps support two turntable inputs but require using RCA jacks. When I add the DIN to RCA converter I get a hum in the phono signal unless I attach an extra grounding wire on the adapter to the amplifier chassis ground lug. With this switch added to the Beogram I can short the phono signal grounds to the chassis ground in the Beogram and not need the extra grounding wire on the cable adapter.

It's doesn't seem like a big deal but it is nice to have options so we are adding the switch to this Beogram.

First I need to removed the faulty muting relay.

This muting relay is different than the one in the Beogram 8002 turntable where Beolover was able to replace it with a new Omron sealed relay device. That relay pin layout is not a match for this Beogram 8000 output signal board. My only option here is to take a newer output relay from one of my later model Beogram 8000 spares.

If I didn't have a spare I would have removed the clear plastic cover and tried to clean the relay contacts. That still might not have solved the problem if it is in the relay coil.

I installed the new muting relay and then attached the grounding switch.

I used some hot glue in the gap between the output board case and the switch case. This helps secure the switch.

Now it is back to the record play testing again. Success of these tests will result in this Beogram being packed up to return home.

Beogram 4000: Installation of a Neutrik Gold Plated DIN5 Plug

Another standard upgrade that I do for Beogram 4000s is installing a new gold plated DIN5 plug. The original ones are not gold plated and tend to be a bit rusty after all these years. This Beogram 4000 was not different:

This shows it taken apart in contrast with the new shiny Neutrik plug (Newark 27B4483) insert:

After cutting the old plug off, I prepared the cable for the new plug. This is a good length for taking the outer insulation off:

It is a good idea to strengthen the signal leads a bit with solder after taking the insulation off. This makes it much easier to solder them nicely into the tabs of the pins. then it was time to solder the plug on:

And here the lovely sheen of new gold contacts:

This is golden beolove!