ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
I still have the Beogram 4004 parts unit that I stole the cartridge mount from on my first Beogram 4000 restoration. I dug out the BG4004 again and checked its tonearm lowering lever. The lever itself was changed from the Beogram 4000 series but the mount is the same. The 4004 still has the spring and snap ring so I will borrow it for this 4000 restoration.
Here are the replacements for the missing parts.
The Beogram 4000 tonearm lowering lever is whole again.
I used Deoxit soaked Kimwipes to clean the switch contacts on the tonearm transport assembly.
The tonearm transport assembly is clean and lubricated now. All of the moving parts move smoothly.
The next step will be the electrolytic capacitors (and some tantalums) along with the trim pots. I will need to pick up some capacitors next week as I know I am out of a few needed for this restoration.
On my first Beogram 4000 (earlier in this thread) I have down that the main board trimmer resistors are as follows -
1VR1 = 50K1VR2 = 5K1VR3 = 10K1VR4 = 20K1VR5 = 2K1VR6 = 2K
On this second Beogram 4000 I have these values1VR1 = 50K1VR2 = 10K1VR3 = 5K1VR4 = 25K1VR5 = 2K1VR6 = 2K
I wonder if I miss-read 1VR2 and 1VR3 on the first BG4000. Once I complete this one I will bring the first BG4000 back to the bench and recheck it. I still need to add the strobe functionality to the first one anyway.
The capacitors that I am going to replace on the main board (board 1) are as follows -
1C11C2 2.2uF, 35V (Tantalum)1C3 220uF, 16V1C41C51C6 220uF, 16V1C7 220uF, 16V1C8 470uF, 6V1C9 2.2uF, 35V (T)1C101C111C121C131C14 220uF, 16V1C15 10uF, 6V (T)1C16 22uF, 6V (T)1C17 0.1uF, 35V (T)1C18 4.7uF, 25V (T)1C19 2.2uF, 35V (T)
1C? 2.2uF, 35V (T)
The last capacitor (1C?) is one that this BG4000 and my first one had added to the trace side of the board. The capacitor is a tantalum and sometimes they can be tricky to identify the polarity. Often there will be small text that includes the capacitance value and a plus sign to identify the positive lead. This one only has color coding. The positive lead is the one to the right of circular dot (white dot in this case).
I replaced the 2.2uF tantalum with a 2.2uF WIMA MKS polyester capacitor. It is non-polar.
1C18 is another tantalum (4.7uF). This one has text markings and there is a plus sign indicating the positive lead. There wasn't any room to replace it with a WIMA MKS capacitor so I used a Nichicon electrolytic capacitor.
1C16 is another no-text tantalum capacitor. It is a 22uF, 6V cap. I replaced it with a Nichicon electrolytic cap.
An easy tantalum to miss is the tiny 1C17 0.1uF capacitor. I replaced it with a WIMA MKS.
This Beogram had a 1C15 10uF, 6V tantalum (shown below) with text markings. The first Beogram 4000 turntable I restored (earlier in this thread) had only color code markings (shown below). I replaced this tantalum with a Nichicon electrolytic capacitor.
The remaining capacitors to replace are three tantalums (1C2, 1C9 and 1C19). All three are 2.2uF, 35V that I replaced with WIMA MKS caps.The three electrolytic 220uF, 16V caps were replaced with Panasonic caps as well as the electrolytic 470uF, 6V cap. The six main trimmers (1VR1 through 1VR6) were replaced. I also replaced the 560 Ohm, 1W resistor (1R19).
A seventh trim pot (50K) was mounted on the backside. This trimmer isn't shown in the service manual but Martin explained it was added to allow sensitivity adjustment for detection of vinyl records that are semi-transparent in color.NOTE: One good thing about taking photos while you work is you catch mistakes. Notice in the picture here that there is a solder pad missing some solder. That is corrected now.
My replacement capacitors for the chassis mounted electrolytic caps haven't arrived yet. They should come in a few days. Normally I would pick them up local at Mouser but this time they didn't have what I wanted so I ordered some from Digikey.Tomorrow I will change out the two 1uF tantalum caps on the power supply board with a couple of WIMA MKS caps (if they fit).I will also start cleaning the switch pads in the Beogram control panel.
This picture shows three of the contact switches of the BG4000 control panel. Pushbuttons press against the flat metal contacts so they make contact with metal plates. The contacts become quite tarnished and could cause problems. I unsoldered the metal contact plates so I could access the surfaces. Then I used a fiberglass pen (a method I learned from Rudy on his Beolover blog) to clean off all the tarnish. After that I coated the contacts with some Deoxit cleaner/protector.
There are four other contact switches similar to the three shown above plus one normally closed contact switch that is under the hinge for the lower board. This eighth switch contact has to be removed so the contact pin and flat, spring part can be cleaned. The first picture below shows the contact cleaning complete and the put back. I cleaned the top side as well.
Here are all the contact switches all clean and ready for use.
I also replaced the two 1uF tantalum capacitors on the power supply board. The C1 capacitor measured >40 ohms on my ESR meter. The other capacitor measured around 3 ohms. I replaced them with a couple of small WIMA MKS polyester capacitors.
My replacement capacitors for the large, chassis mounted electrolytic capacitors (0C1, 0C2, 0C3, 0C4, 0C6 & 0C7) should arrive tomorrow. Once I get those all changed out I should be ready to start on the mechanical and electrical adjustment procedures. Still quite a bit of work to do.
A nice new tonearm drive pulley arrived from Nick yesterday. Here it is installed on the Beogram. Unlike my first BG4000 turntable, this one still had its felt washer.
Nick and Rudy are the best, and so are you John!
Great work, as always.
Happy New Year!
Jacques
Just got my BG 4002 in, so I am following and learning, thank you John
Collecting Vintage B&O is not a hobby, its a lifestyle.
Thanks Jacques. Speaking of Rudy... Søren, make sure you go through Rudy's Beolover blog posts about restoring the BG4002. He has some really good videos that show a lot of details on how the turntable works.
John
My replaced capacitors for the Beogram chassis caps came today so I started in on changing those out. The bigger capacitors should be easier to work with but the wiring on this Beogram make this task quite the chore. Here are the original 0C3, 0C4, 0C6 and 0C7 capacitors as I am removing them.
Here are my replacements. From left to right - 0C7, 0C6, 0C3 and 0C4.
The hard part is rewiring the connections to the capacitors. Here are the rewired caps.
I also replaced 0C1 and 0C2. This picture shows the chassis mounted capacitors recapped and secure in their positions again. I was able to reuse the original metal clamps that hold the capacitors in their place.
The project is getting closer to the adjustment procedures. I just have a few more parts to replace before I will be ready to try applying power. I sure hope this Beogram's transformer has life left in it. If not, I'll have to order another toroid replacement transformer.
Tonight I looked over all my work so far and decided it was time to do a power test. I also wanted to see what the voltage measures across the scale illumination lamps. I put my DMM across 3IL3. When I pressed the Beogram start button the lights came on and I have a 10.94 VDC drop across that lamp. The supply voltage to that circuit measures a little over 25 VDC. The platter motor and the turntable motors started turning (I don't have any belts on right now). I also get the strobe lamp firing. All that and no smoke .
Another reason I wanted to check the Beogram with power before I continued is because I would like to use a couple more of Beolover's replacement parts. One part is the replacement relay for 7600007. That is the speed select relay on the main circuit board. Rudy makes a nice drop in replacement for the original relay with a new, encapsulated relay. Here is a good video about the replacement part. A nice thing about Rudy's replacement parts is that they retain the original part mounting footprint. That is important because someone may want to put back an original style part and they will be able to do that. Before I change the relay out though, I wanted to test if the original part works. This picture shows that the speed does switch between 33 RPM and 45 RPM when I press the speed buttons on the control panel.
This picture shows the original Siemens 7600007 speed selection relay and the Beolover replacement relay assembly. You can see that the pin outs match the original part footprint.
Another Beolover replacement parts is an LED lamp assembly to replace the Beogram control panel scale illumination. On the BG4000 this replacement was a little confusing. My BG4000 control panel board with the lamps looks like this.
Comparing my board with the BG4000 service manual I have this difference -
My board has 12V lamps and the service manual shows 12V lamps. However, the +24V source wire looks like it routes differently. The confusing thing to me though is the service manual has a note about a correction to the circuit and appears to say the lamps are now 24V lamps.
The service manual schematic shows this which seems to match what my control panel board has. I measure +25 V as the source to the scale illumination lamps and I measure +10.9 V across each lamp.
One of my current scale illumination lamps is marked as 12V so I believe I can replace those lamps with 12V equivalent lamps from Beolover. Here is a picture of the Beolover replacement lamp assembly. Some people may be opposed to using LED replacements because they are afraid the turntable will not look original. Rudy has taken time to adjust the color output on these lamps to match the original lamp color. However, if the result turns out to be unsatisfactory, it is easy to put back the original lamps.
Because of my confusion over the type of scale illumination lamps I incorrectly ordered the Beolover replacement LED part that is adjusted for 24V. I should have paid attention to what my lamps on the board said. So I'll have to exchange the lamp replacements for the correct 12V ones. For now I will leave the lamps alone and continue with the restoration.Today I replaced the speed selection relay with the Beolover part. The new replacement doesn't require a ground pin that the original Siemens relay has. Here are the parts side by side.
Here is the new relay installed. It makes a nice, soft click when it activates so there is still that sound to assure you that it is working.