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Hi all, I am new to the forum, tried to search for a thread on my issue but I couldn't find it so I want to ask:
I have purchased a Beogram 4000, cleaned and lubricated everything, and everything looks and works nice, but I have a strange problem. When I lower the arm the sounds comes about a second after the stylus touches the LP and after about 2 seconds I lose the sound on the right channel. The left channel continues. I switched the cartridge with a tested and working mmc4000 and still the same problem so I am thinking it is not the cartridge.
Could this be something with some capacitor in the unit. I had it shipped although it was packed quite Ok all transport screw tightened cartridge and turntable separately packed, tonearm secured etc.
Much curious if u can fix this, your help us appreciated.
Besir
Hi and welcome to the forum,
All and more information you might want on the Beogram are in this thread and this blog. It sounds like there could be a problem in the muting relay but the only way to know for sure is to dive into it. The two links I provided should show you the scope of the restoration work the Beogram can require. If you aren't experienced or have the technical expertise to do the restoration yourself I would not recommend learning on this turntable.
-sonavor
Hi Sonavor,
Many thanks for your quick response and the pointers you have provided. Wow! i might be way over my head here. I have a beogram4002 and i had to fix its mechanical parts, solenoid and the vacuum cylinder were seized up etc, but nothing electronic. So i am scratching my head here. But i am an engineer by training so i am now very curious and will try to figure out how to approach this problem. In the meantime, if anyone knows a good technician capable of helping with this unit in the amsterdam area in the netherlands, that would be a great help i guess :)
-besir
Hi again. Well it sounds like you have the background and skills to tackle this type of problem. To me, the electrical part of the restoration is pretty straight forward. It is all of the mechanical adjustments that take the most time. As you can see from Beolover's blog, he has produced some nice reproduction parts for a lot of the electrical problems. Martin (Dillen on the forum) also is a good source of parts, including capacitor kits for replacing the electrolytic capacitors. He also has belts for the Beogram.What is the condition of your Beogram 4000 cartridge mount? Does it appear intact and in good shape?
The cartridge mount appears good and intact. here is what happened last night:
Things got worse, i was looking around and poking around a bit, i accidentally shorted something on the circuit board 2 (the one next to the power source) now the controls are a bit messy, the on button starts the turntable but doesn't move the arm, so i have to move it manually, so i have two problems now. I am so angry with myself :( !! i should have been more careful, expensive learning experience...
Later focusing on the first problem, i followed your advice to take a look at the muting delay, although the flaps were a bit to close to the switches (there is some lag in the plastic piece that opens the short circuit) that seems to be ok. I still put a toothpick in between and tried. Still the same.
Next i started measuring the resistance wrt to chassis at the din connection points to see if i have any shorts. I found that RL connector (green one in this picture: http://beolover.blogspot.nl/2015/05/beogram-4000-grounding-and-hum-issues.html) has a short. Strange thing is the short is intermittent (or perhaps my multimeter is not good, its quite a cheap thing). I don't know if i am excited for nothing but that shouldn't be normal right? I need to trace it back i guess, what is your suggested approach here? should i dismantle the circuit boards, i am a bit scared to do it, and i don't have a proper workspace, I share my desk with my wife :( and she is putting some looks on me ;) I want to be able to diagnose as much as i can and order/find parts necessary before start something big so i don't have it lying around for too long. Also if i look around and buy a broken deck is that a useful idea? It is hard to find 4000 units but sometimes i see 4002 4004 units? would they be useful for parts for this project?
Many thanks for your help Sonavor, much appreciated.
Ouch...I've been there before. It is always torture when you make a mistake like that and electronics don't have an "undo" button like software does.There are a few mechanical parts shared between the Beogram 4000 and the 4002/4004 series but that is about it. Maybe a couple of electrical parts but if you look at my thread you can see that the turntables are really quite different. The circuit boards and transformer are completely different.First thing I would do if I was in your position is check the voltages in the power supply and see what the current state of the main voltages are. Try to determine what you shorted. Do you have a picture of the area where you shorted the circuit? You also must have a Beogram 4000 service manual. I would estimate that the project will tie up your work space for quite a while. You'll have to work that out with your wife . Where are you located? Before looking for a parts unit (which will be difficult to find), you should look at having an experienced repair person salvage what you have. You can still learn the mechanical adjustments later but first thing is to get the electrical part working again.
I downloaded the service manual, but i am not very good with electronic circuit diagrams - although i have the basics so i will work on that.
i tried to insert an image here, but somehow i couldn't, put i uploaded it to the forum, can you see it at this link?
http://archivedforum2.beoworld.org/members/besir660/files/Screen-Shot-2016_2D00_03_2D00_13-at-22.28.28.png.aspx
Thanks - besir
oh by the way, i live in amsterdam - the netherlands.
besir: i tried to insert an image here, but somehow i couldn't, put i uploaded it to the forum, can you see it at this link? http://archivedforum2.beoworld.org/members/besir660/files/Screen-Shot-2016_2D00_03_2D00_13-at-22.28.28.png.aspx Thanks - besir
besir: oh by the way, i live in amsterdam - the netherlands.
I see that in your profile now. There should be some Beoworld members with Beogram 4000 repair knowledge not too far from you. You might send a Beoworld private message to Dillen (Martin, who is in Denmark) and Chartz (Jacques, who is in France) if you can't find anyone in the Netherlands.-sonavor
I appreciate this so much, thank yo.
Thanks a lot so far. i need to get some equipment and open up some work space and dig into it. I guess i will work on this myself a little and if i mess it up completely then i will find someone to fix it for me.
i still want to get your opinion on the sound issue:
(green one in this picture: http://beolover.blogspot.nl/2015/05/beogram-4000-grounding-and-hum-issues.html) has a short. Strange thing is the short is intermittent (or perhaps my multimeter is not good, its quite a cheap thing). I don't know if i am excited for nothing but that shouldn't be normal right? I need to trace it back i guess, what is your suggested approach here? should i dismantle the circuit boards, i am a bit scared to do it, can i trace it without dismantling? The thin wires look too fragile to me, and if i break somthing without knowing where it was connected to i will be in a mess.
my thinking is that since i dont lose the sound immediately on the right channel but in a second or so, i am thinking maybe there is a capacitor on the path which shorts it (also could be the reason that the short doesn't read consistent on the meter)
for the control circuit, do you think it is an idea to replace the whole thing by an arduino project or something? i realized that most of the electronics in the body is related to controlling the tone arm whereas the circuits for the sound signal is pretty straightforward..
I appreciate this so much, thank you.
The phono cartridge output signals are just a straight shot out of the beogram. However, the signals do go through a muting switch over by the solenoid as you reference in the Beolover blog. There is a mechanical adjustment for the position of that switch operation. Maybe your switch is corroded or out of position.
I would never consider replacing the control logic of the Beogram with some modern micro controller solution. It would lower the value of the turntable and there isn't really any need for it. When the original switches are all clean and aligned the Beogram works perfectly. The electronics on these old analog systems work great. Most of the work in getting these turntables working properly is the fine tuning of the mechanical adjustments. As I said before, the restoration is just a slow, steady process. Take the time to learn how all of the pieces work and take your time to get them back into working order per the service manual. Then you will be rewarded with a beautifully working, classic turntable.
One more question and i think i will be out of your hair for a while, and will hopefully emerge with a gorgeous working beogram 4000 :) or will come out looking for an expert guy in my area :P
should i invest in an oscilloscope or is a multimeter sufficient for the job? i see a large range of prices for oscilloscopes (~ $150-$1000), 1 channel oscilloscopes are cheaper, but i don't know if they do the job (that is if i need one)
Many thanks
SOME EXAMPLES:
https://www.conrad.nl/nl/velleman-hps140i-kanaal-hand-oscilloscoop-complete-set-met-voelkop-accu-usb-lader-bandbreedte-10-mhz-122450.html
https://www.conrad.nl/nl/voltcraft-6102-analoge-oscilloscoop-1-kanaals-10-mhz-122413.html
https://www.conrad.nl/nl/rigol-ds1054z-digitale-oscilloscoop-50-mhz-1392205.html
https://www.conrad.nl/nl/rohde-schwarz-hmo1002-digitale-oscilloscoop-2-kanaals-50-mhz-1214052.html
If you are wanting to dive into this hobby of restoring vintage audio components then yes, an oscilloscope is a very useful tool. Several brands offer decent digital scopes with storage. You only really need 2 channels and typical digital scope frequencies of 30MHz, 50MHz or 100MHz are well above the audio range. Rigol is a nice scope as are Owon and Siglent. You should be able to get one for under $400 USD. Other options are oscilloscope packages that use your home computer like this QuantAsylum but I like having a stand alone scope first.
You will still use the multi-meter most often so it I would recommend getting some good probes for doing those measurements. Some tiny mini-grabbers and regular mini-grabbers. With the small clips you can safely probe some places on the board that a large probe would short out.You should also get a good desoldering gun and soldering gun.-sonavor
I m back, i've been fiddling around a bit, I might have found the source of the sound issue (where i was losing right channel after a second or two). Look like the cartridge mount is bad, when i touched the 1&2nd ones from the right (as seen on the mirror) i get a short. I am attaching some pictures? I am really feeling down, this I think is a bad situation? I think i need a 3d printed part replacement and i am really clumsy with the tiny wires and solders. Do you think i can save the situation without getting the arm out? I attached a picture, which is a mirror image.
There should be a short when the tonearm is not engaged with playing a record. That is a function of the muting switch. To actually trace the individual phono signals from the cartridge mount all the way to the output plugs you have to manually separate the muting switch so it doesn't short the high to the low phono channels.
The picture of your Beogram phono cartridge mount looks good. Nothing appears to be loose and no signs of tears in the plastic or separation of the traces. I think you are in good shape there.
-sonavor.
Thanks Sonavor,
You're right, I guess it was a bit too late at night, my mind was a bit spongy. i realised the muting switch is actually shorting it, i tried as you mentioned and no short. But still, i get a moment of sound on the right channel and then it's gone. really strange problem. I am stalled.
Are you sure the mechanics of the muting switch are functioning correctly. Check how much the switch opens up when the Beogram is playing. There is an adjustment procedure in the service manual for positioning those switches that operate off the solenoid mechanism.
Yes i am thinking the same, i will take a look. But previously i had put isolating tape between the swithces and i still didnt get aound on the right. Maybe it there is something wrong in the circuitry of that switch? I will take a look and will report if any progress.
If you insulated the switch contacts to disable the muting and still experienced a channel dropping out then the problem is either a loose connection (solder joint issue or almost broken wire) or a problem with the cartridges. If the cartridges work fine on other turntables then there must be some sort of wiring problem.There are a number of solder points in the path from the cartridge mount out to the external phono cable. What about the phono cable? Did you check the integrity of the phono cable and its connector?
I have checked the integrity of the cable. check.
I dissambled the tone arm to check cartridge mount connections inside and the back to back solder unit underneath. check
one thing i came across is the low signals of left & right are connected together (on the mute relay and then again on the circuit board just before the cable exits the body)
still need to check the transfer of signal on the muting circuit, but wanted to shoot the question in the meantime.
is it ok to have the low signals joined for both channels or is this the reason why one channel drops?
thanks a lot as usual.
The two phono channel low sides do get joined then delivering the phono signal to the cable. That is how it should be.
Looking back at your first couple of posts about this problem I think one part of your problem (delay of when the muting relay opens) is due to the mechanics of the lever that controls the signal muting. There is an adjustment procedure in the manual for moving the position of the muting switch board to control when the muting switch disengages. If you haven't fixed that part then you will need to go through that.
With regard to the second part of your problem being the intermittent right channel, it can happen anywhere on the record? The intermittent nature of a signal that just goes through wiring and connections makes me still guess the problem is mechanical (solder joint, break in a wire). It sounds like it involves some sort of movement to produce the problem so some hairline break is sometimes making contact. Another possibility is something coming into contact with one of the wires when the tonearm carriage is moving. It is hard to say without actually seeing it. When the right channel goes out does it stay out or does it cycle on and off?One thing to remember is that there could still be a problem with the mounting tab and wiring in the tonearm even though it visually looks fine. If I were working on it I would try to devise tests to pinpoint where in the path the problem originates (before the muting switch or after the muting switch). You might even try making a temporary phono wire run from the tonearm carriage to the output cable (bypassing all of the wiring through the muting switch to the output cable). That would tell you if the problem is up in the tonearm area.
I got audio!
Turned out the solder on the red wire solder point under the tonearm (on the circuit board where thin copper wires from the cartridge gets crossed over to the color wires) was broken and the wire had intermittent contact. I fixed that, so now I have sound. In the process the tone arm adjustments went haywire of course, but i managed to roughly adjust it to get the sound. I will fine tune when i can work on it. You were right about the suggestion of a wiring/connection problem.
now, what drives me crazy is that the control circuit is full of gremlins because of the short i caused. Some symptoms:
1) When i plug in the turntable, the arm starts moving and doesnt stop until the end of the platter. I need to stop it. also the default spinning is 45rpm
2) Then when i press ON it starts spinning the platter but doesn't move the arm. I need to move it using the control panel
3) Lowering and raising the arm controls work.
4) backward control is flimsy, sometimes works sometimes very slow or doesnt work
5) when it stops, the platter stops and the strobo light turns off but other lights (position slide, sensor arm light) stay on.
I think i have to figure out and trace the whole circuitry. I shorted something on the left side of the circuit board just below the power supply (the board where components face up). Do you have any suggestion what is the best approach to start?
Check the voltages of the Beogram power supplies and verify you are getting the correct DC voltages on the power rails (24 VDC and 6 VDC). The operation logic on the Beogram comes from the NAND gates on the control panel. I don't think it is likely that those are bad. From what I have seen and others have reported, they are pretty durable. The control logic of the Beogram is made up of a lot of signals from sensor switches. You will need to learn where all of those originate from and what they control. It took me a lot of iteration to get the control switches adjusted. The forward and backward control (fast and slow speed) adjustment can mean removing the flat leaf contacts of the switch, adjusting it and reattaching it so that the control bar operates it correctly. I will warn you that those adjustments can be frustrating. The tonearm position switches press leaf contacts on the underside of that board so they may need to be examined as well. I monitored the control signals going to and from the NAND gates though to see if switches were operating or not.
Found some time to look into it a bit. I don't know how to look at the power supply voltages, and where exactly are the power rails? will try to figure that out
in the meantime, I looked at the voltages in the control circuit lights (easy something to do :P). service manual diagram shows 12V, and I have 9.76/10.55 as seen in the picture. Could this be causing my gremlins or is it just my bulbs are bad?
sorry for stupid questions. :^I
best-besir
ok i figured out where the rails are, i think my voltages are not good. 15.5V and ~4V. But maybe it was always like this, it can still drive the motors i think because things move :)
...and the next picture
I have a lot of heat on the silver transistor (2TR6? circled in the picture). I can also see a bit of burned area on the sleeve of the blue rail wire.
besir: ...and the next picture
An AC measurement at your DVM probes in your picture should measure 10 VAC.
Here is the 24 VDC rail voltage at 0C4 on my Beogram 4000
Here is the 6 VDC supply voltage at 0C2 of my BG4000.
Dear Sonavor,
I couldn't work on this for a while. I now checked the voltages (thanks for pointing out) i think they are ok, only at 0C4 i have 24.3, but is that a big issue? I am thinking 2TR6 in the PCB 2 (the one near the power supply where i made a short) is shot. It gets really hot. It is the silver thing (i posted a picture in the previous post), i don't know what kind of transistor it is, will need to figure that out and replace I think. Could that be causing my control issues?
I hope i am not becoming a burden, thanks a lot.
besir
besir: I am thinking 2TR6 in the PCB 2 (the one near the power supply where i made a short) is shot. It gets really hot. It is the silver thing (i posted a picture in the previous post), i don't know what kind of transistor it is, will need to figure that out and replace I think. Could that be causing my control issues? besir
I am thinking 2TR6 in the PCB 2 (the one near the power supply where i made a short) is shot. It gets really hot. It is the silver thing (i posted a picture in the previous post), i don't know what kind of transistor it is, will need to figure that out and replace I think. Could that be causing my control issues?
Not necessarily. 2TR6 is managing your Beogram 6 VDC supply. If you have that voltage then it sounds like it is working. Monitor the voltage across the 6 VDC supply capacitor, 0C2. Does it maintain a steady voltage of around 6 VDC (while trying to lower the turntable and when the tonearm carriage is moving)? If it does, I would guess 2TR6 is okay. If the voltage is flaky then you can worry about the power supply. If your 6 VDC supply is fine you need to start from the solenoid that lowers the tonearm and find the source of the problem. Is the solenoid trying to engage or is it not getting any command to engage? Is the logic that commands the solenoid to engage (Ǭ₁) trying to engage it? Or does the logic instructing the solenoid never firing? Those conditions need to be figured out determine where the problem area is.
On my Beogram 4000 turntables the lead from the solenoid that goes to 0TR4's collector is around +28 VDC (maybe even a little higher) when the solenoid is not engaged. When the solenoid is commanded to engage and lower the tonearm, that line will drop to around zero volts very briefly (10 to 12 milliseconds), then settle at around +24 VDC. It's hard to check with just a DMM. You can read about the tonearm lowering signal operation here. What goes on with the tonearm lowering control signal (Ǭ₁) during the process when the tonearm should be lowering? Does that voltage ever go low? If that signal doesn't go low to turn off 1TR10 then 0TR11 will remain off and 0TR4 will remain off and the solenoid will never engage.
Be very careful measuring around the solenoid. The two leads from the solenoid to the small circuit board are both typically at around 24 VDC to 30 VDC. If you measure those you will want to unplug your Beogram to set up your probes, take measurements, then unplug you Beogram when you want to move the probes.
The tonearm works, so i can lower it and raise using the control panel.
I also checked the voltage across 0C2 during operation but it seems stable.
my issues are strange:
-when i plug in the unit, the arm starts moving across until the end. i have to stop it. when it stops, the platter stops, but the light stay on.
-when the arm is back in the start position and i press start, the platter starts spinning but the arm doesnt move. i have to manually move it and lower onto the record.
What i did is to try to test 2D 4, 2TR6 and 2TR7 using my multimeter. 2D4 seems shot, and i am attaching the picture of the 2TR6 test (you can see the circuit reflected from the mirror so it is at the same point as in the diagram showing from component side. I have 0.612 in one NP measurement (i assume the middel point is the P) and this seems closer to silicone value around 0.68, but the other/PN measurement reads 0.12? and like i mentioned this one gets super hot (it burns you when you touch it, i dont know if thats normal)
2TR7 seems ok
I tried to find if i can find it (type BC 119) and checked possible alternatives in alltransistors.com, but seem like difficult to find.
what do you think.
..and the other measurement on 2TR6
Since the power supply board does not contain any logic regarding the operation of the turntable I would say you have problems elsewhere. The control switches and the sensor switches would be suspect. However, the power supply does provide the power for the rest of the turntable to operate. I think I would still monitor the control lines for the operations that are failing to understand what is going on. Take the belts off and see if the motors turn when they are supposed to. Operate the detection switches manually and see if they control the motor operation correctly. As you should have read in my Beogram 400x thread, there are a lot of adjustments to be made. Those include checking the platter motor amplifier output and adjusting that drive signal. You don't know what condition that signal is in. The transistor in question on your power supply does appear to be too hot though. I believe mine only heats up to around 34 degrees Celsius. Ask Martin (Dillon on the forum) about replacing the transistor. You might also ask him to move your thread to the Workbench rather than General Discussions and Questions.
ok will do so and check back in later. many thanks!
I report success! The 4000 is back in business. I replaced 2tr6 and 2d4 which looked shot when i tested them with the multimeter. I am not sure if transistor was really bad but the zener diode was a goner. So somehow i am good :P
Bit now i have a very different problem, this never ends...
once everythjng is working i focused on cosmetics. Soem owner in the past had scratched some kind of number on the bottom of aluminium pmate which is above tbe control panel. I decided to get rid of this and sanded it away (in straigt lines and keeping prallel with the brushing) however turns out the aluminium is coated (?) now the scrathes are hine but i have an ugly patch of shiny metal. Can any point me in the rigt direction on how to refurbish the aluminium panels, what kind of coating is it, etc. i will attach a picture.
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