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I have a 4002 and when I press play the arm comes across nicely and drops onto the record but the record won't spin!? There is no response from the drive motor at all. Anyone suggest any possible solutions?
check the belt
Collecting Vintage B&O is not a hobby, its a lifestyle.
What type of Beogram 4002 is it? There should be a sticker underneath the turntable and one inside (at the back) that states what the type is. For example it will be a number between 5501 and 5523. Early models have an AC platter motor, later models have a DC platter motor. You will have to open the deck to the turntable to observe if the motor is running when it is supposed to.
-sonavor
The type is 5504.
At first I had no power so replaced one of the small glass fuses which had blown and now the unit powers on and the arm moves across when I press play and 33 or 45 and then drops down onto the record at the right spot but the record is not spinning!
I have tried doing this with the belt on and off but the actual motor itself is not spinning.
Pic shown below - (am I right in thinking the bottom left plastic wheel is the driving one and should spin the belt turning the platter?)
Okay, you have an AC motor with the nice, heavy platter. You will need to monitor the motor amplifier output and see what kind of signal, if any, is present. The voltage should be close to 6 VAC (VRMS) and a nice sine wave. If the signal is there and the motor isn't turning, then the motor is probably faulty. If the signal to drive the motor is not there, then the problem is most likely somewhere in the motor amplifier circuit. Also make sure the power supply is providing power to the platter motor amplifier. On my Beogram 4000, which has the same type of motor, I was having issues with the motor not turning all the time and the problem was a loose wire on one of the chassis mounted transistors. Looking at your nice picture, it appears everything is original inside. I recommend doing a complete restoration on it so it will be like new again.
Hi Sonavor,
Thanks for your great reply. How do I go about testing the power to the motor amplifier?
I can get hold of a multi-meter but wouldn't really know where to start.
I'll check all the wiring this evening for anything obviously lose.
I do believe everything seems to be original.
Harry
Ideally you would get a hold of an oscilloscope but that can wait as you can use a DMM to check the AC and DC voltages. If you don't have a service manual you will need to get one. You can get a digital version via Beoworld with a Silver membership. Once you have a service manual we can point you to what pins you need to measure voltages on. Starting with a DMM I would check the turntable power supply first, then work your way to the motor amplifier power rail (22.8 VDC in the service manual). That will tell you if the amplifier can be expected to be putting out any signal. The actual sinusoid signal that drives the platter motor is measured between the two motor capacitors and is expected to be about 6 VRMS (at 42.3 Hz for 33 RPM and 57.3 Hz for 45 RPM). If that signal is dead, then you will need to dig into the amplifier circuit. It may just need new electrolytic capacitors. There could also be a problem with the trimmer resistor for the motor platter. It may need adjusting. This is where you need an oscilloscope. You need to make sure the 6 VRMS (42.3 Hz and 57.3 Hz) sinusoid is good and not clipped.
If you don't have the capability to work on that part of the circuit I would strongly suggest you farm that task out to a Beoworld repair person near to you.
Forgive me for asking, but do you have any electronic education at all?Tools, instrumentation, experience etc.?Don't get me wrong, it's just that a B&O tangential deck is not the easiest thing for a beginner.
Martin
Thanks for your comprehensive reply Sonavor.
To be perfectly honest I think the repairs are a bit above and beyond me so I will most likely take the latter piece of your advice and source a reputable technician to repair.
Failing that I will just sell it 'as is'.
Thanks again for your efforts and pointing me in the right direction.
hjb_1990: Thanks for your comprehensive reply Sonavor. To be perfectly honest I think the repairs are a bit above and beyond me so I will most likely take the latter piece of your advice and source a reputable technician to repair. Failing that I will just sell it 'as is'. Thanks again for your efforts and pointing me in the right direction.
Wise decision! Something I also did with my 4002! I sent it to the experts when there was an issue with the motor, was sorted fairly easily and quickly luckily.
It is important to know when to not continue!
Ben
Hello John,
With interest I have gone through your reply to this motor issue as I have experienced just the same
Problem this afternoon.
It started out that my BG4002Tpye 5503 started spinning at 45rpm after 'on' was pressed.
According to the fault-finding chart both 1TR3 & 1TR4 should have been 'high' & 'low' respectively on their collector, reason to find in the Wien-Bridge oscillator.
I replaced 1TR5 & 1TR6 together with 1TR7.
The table now started with 33rpm as it should, however the platter motor wasn't spinning ?????
Before all this happend I did a routine voltage check of the motor voltage according to the SM with my
oscilloscope and everything was fine!
Now I can't get it to spin........checked the amplifier voltage 'out' and various other voltages......all seems fine ?
Next suspicion was a dead motor......replaced it with a working spare motor just to check.....same story!?
Checked that famous trimmer resistor 1R27 which showed its full range of resistance as specified.
Also checked OTR2 &3 for loose wires at their legs......all fine ?
The platter-motor just does't seem to get any - checked again to adjust its voltage via 1R27.....flat line!
Really could do with some expert guidance here - definitely far too nice a table to part-out.
Cheers, ALF
Hi Alf,
It is difficult to remotely trouble-shoot this type of problem but here goes. When you say that the table starts with 33 RPM as it should I take that to mean you can start the turntable play mode but the platter motor isn't driving the platter, right?Did you go through the adjustment of section 5-2 in the service manual? You need to examine the motor amplifier output signal with your oscilloscope to make sure it is the proper amplitude and frequency (and isn't clipped). If that amplifier signal is not correct the platter motor can not operate as you are experiencing.
Have you also checked OC3 (4000uF) and OC4 (150uF - bipolar) capacitors? Maybe your Wien-Bridge oscillator isn't functioning.John
Hi John,
good to hear from you ☺️
Yes, that is correct: table in play mode !
speed selector shows 33rpm, C at 1TR3 = 159mV, C at 1TR4 = 22.2V - platter motor not spinning !!
Amplifier section:
1TR7: B = 0.63V, C = 8.7V,
1R30 = 1.57V
1TR8: B = 1.58V, C = 10.4V
OUT = 10.85V,
B1 = 11.38V, B2 = 10.44V
B at 0TR2 = 11.6V, B at 0TR3 = 10.6V
oscilloscope shows a flat line at platter motor voltage even after fitting a new 1R27 trimmer pot !!
it puzzles me as the motor was spinning before replacing 1TR5 and 1TR6 in the Wien Bridge as the table in play-mode started at 45rpm ?!!
I can vouch for that as I re-adjusted the motor voltage with the oscilloscope before all this - it was just a tick noisy, which disappeared as soon
as I established the correct sine-wave shape without any distortion or clipping !!
why should it be dead now ? All the voltages appear to be there, though not absolutely correct according to the circuit diagram.
there must be a simple reason for that issue ?!
cheers
ALF
If I am understanding your original problem, the Wien-Bridge Oscillator was working in 45 mode but not in 33 mode. After changing transistors there is now no output from the oscillator. Did you check the components you removed to verify they were defective? Are you sure the pin outs of the new components matched, exactly, the ones you replaced?
Also check the lamp 1IL1 to make sure it isn't burned out or damaged. It has to be good in order for the oscillator to function. Last, check the components, including trimmers, in the path for the speed selection. That is where the oscillating frequency is determined.
John
Guilty as charged - 1TR5,6 & 7 turned out 'good' off board ! They have been replaced with exactly the same new types !
So, that should not have had any impact ?
I examined 1L1 - it measured about 23 Ohm and had about 8.8V at both legs.
The positive terminal of 0C3 measured about 11V.
All trimmer pots should their full range of resistance.
PO, PO3,4 all showed about 8.7V.
The only thing I can still not see is the sine wave at the motor measuring point, nor can I find a suspect component.
Can we absolutely rule-out a motor damage ????? (Just asking !) All components of the Wien Bridge-oscillator seem fine.
Must admit I am not quite clear about that oscillating function - is that creating the AC voltage for the motor as I obviously measure
A DC voltage of around 11V at the positive terminal of 0C3 ?
I sense, this is difficult but needs to be fixed:-):-):-):-):-)
Cheers ALF
There are actually two separate inputs and feedback parts to the oscillator. One for 33 RPM selection and one for 45 RPM selection. Your original problem was with the 33 RPM signal not generating so that problem is probably still there. Now the 45 RPM selection doesn't produce a signal so something had to have broken there. From that information I don't think the motor is the problem. Remove the motor and verify the oscillator output is still flat. Also, check the lamp again...this time out of circuit.
Thanks John,
I will start with the lamp first - just remembered I had a similar bulb issue where there was not open circuit as resistance measured greater zero but the bulb was faulty !!
Will get back to you to report findings.
Cheers
Taken out the 1L1 Wien Bridge Bulb and measured exactly 22.9Ohm, nothing loose inside the Bulb !
Disconnected the motor, made no difference - still no oscillating output signal !
I can see the two parts for 33 and 45 in the Wien Bridge Oscillator - well, TR5 & TR6 are new, C6, 7 &13 are spot on, all trimmers seem to work as they should........haven't checked the resistors yet.
It has to be a common part for both -33 and 45 - that prevents from the oscillator to generate the desired output as there is no signal at noth selected speeds.....but which part ????
Really love to crack that problem :-):-)
It makes sense that the motor is not the problem. Have you checked all of the capacitors in the circuit?Also check what is going on at the 33 RPM and 45 RPM inputs to the oscillator. Measure the voltage at 1R10 and 1R23 when you start the turntable and again when you press the 45 button.John
You are absolutely right, on reflection the sine-wave should be there with or without motor !
As suggested, turning ON and switching from 33 to 45:
1R10 = 8.2V (on & 45)
1R23 = 8.8V (on & 45)
33-oscillator input with table in 'ON' mode
1R8 = > 22.2V at 45 and 160mV at 33.
1C6 at ‘+‘ 8.18V and '-' 8.7V
45-oscillator input with table in 'ON' mode
1R11 => 22.2V at 45 and 180mV at 45
1C7 at '+‘ 8.19V and '-'8.7V
Does that make sense ??
You said you have -1R8 = > 22.2V at 45 and 160mV at 331R11 => 22.2V at 45 and 180mV at 45 Did you actually have? -1R11 => 22.2V at 33 and 180mV at 45 There must be some broken connection or failed component in the oscillator circuit.You said you checked all of the trimmers (2R1, 2R2, 1R21, 1R24 and 1R27). Are you sure you don't have any of them turned too far out of position?I would try setting 2R1, 2R2, 1R21, 1R24 to their mid-point, then adjust 1R27 to see if you can get the oscillator sine wave to appear.What about 1C6, 1C7, 1C13, 1C14, 1C15 and 1C16 (the electrolytic capacitors)? Did you check all of them?John
Yes, that is correct 1R11 sees 22.2V/33rpm and 178mV/45 measured on the 'speed selector' side !!
If I measure on the Wien-Bridge side I get about 8.2V for 33&45 !!
Only suspicious caps were 1C13 & 1R16, but both checked out fine off-board!
I had all trimmers set to their center-position - 1R27 position I know well from previous adjustments.
Sadly no oscillating signal
I am not doubting your suspicion, I simply can not find the bugger.......
2R1 and 2R2 I did not check as both have not been changed in a long time, besides it seems extremely unlikely
both of them are playing up plus I got a measurement for P0, P03 and P04.
Do you have a special method of testing 1IL1 - as far as I am aware it's not supposed to light-up ??!
It looks like a 'cat & mouse chase'
Hi ALF,
I have a 4002 AC motor BG so I thought I'd post an original picture that may help???
From what I have read I am thinking that 1TR7 is the problem. Did you replace it with a TO-39 packaged BC-142?
The lead identification tab should point towards R17 - see below photo. The flat face of 1TR5&6 that you replaced should be facing away from TO-39.
Anyway keep at it, you'll get there in the end.
Regards
Lonnie
Hello Lonnie,
Good thinking - thanks for caring, (un)fortunately all is fine in regards to BC142 transistor as well those other two mentioned.
So, the search is still on.......naturally any help is much appreciated !!
Take care and enjoy your BG
Alf, From the diagram I posted earlier, the output of the oscillator is the node where 1TR7 collector, 1R26, 1R25 and 1C14 meet.I am wondering if the oscillator is actually working but, perhaps, the amplifier section is failed.I don't know if the unamplified oscillator output is measurable by your oscilloscope at that node (1TR7 collector) but it might be worth checking. You might even pull out 1R27 and make the measurement at the 1C14 negative lead. John
Hi john,
I measured all suggested options but no oscillating signal I am afraid
I wonder if we need some devine intervention ???? It is hard to believe the culprit can not be found ?!!
As you said I would agree with the osscillator is not working but there are only so many components involved seems to me as
we missed something trivial here ?
Does the oscillator not getting the correct signal or is theree something else in the oscillator circuit faulty??
I double-checked 0TR2 which was ok........just running out of ideas - what is the common link between that issue here as there is
No platter-spin at both selected speeds?
No problem about the caring, you've got a great little mystery going on here and I'm looking forward to the solution.
I noticed in a previous post that you flagged that 1C6,7 & 13 are spot on. I presume that you removed them from the board to test them??? Have you checked and double checked that 1C6&7 are correctly re-installed?
Are you able to upload some photos of the component and solder side around your Wien bridge oscillator? I/we can help check your work without asking dumb questions like the one about 1C6&7 above and my previous one about 1TR7
Hi Lonnie,
No question is dump with the right intention behind !! Easy mistakes can be made and no expert is imune.
Problem with uploading pics is they all are too big, despite choosing the smallest size on my tablet.
I can try again but you will have to use the picture link to see the pic in one hit to enjoy - maybe you can see what I can't ?!
I haven't work out how to make them smaller either, my last pic is evidence of that!
1 extra thought:
1R17 & 1R18 join together at one end and the other ends join via 2R2 (1K) on board 6140376 (45 rpm adjuster on the keyboard). Can you measure the resistance between 1R17 & 1R18 to make sure that the wiring that goes from the main board to board 6140376 is intact. Do the same for 1R15 & 1R16. If it's ok it will measure less than 1k and if it's not ok it will measure ~60k.
FYI about posting pictures on the forum. Since a lot of us use some sort of device with a digital camera, the pictures are some default resolution that is usually pretty large. That allows for editing down so you start out with a nice high resolution image. If you go directly from the camera to a forum post however, the image is too big to view nicely in the web page. What I recommend doing is to upload your images to a computer and create a web friendly, edited version of the picture for posting. Some smart phones and tablets have editing features built in as well. I have found that images that are around 700 pixels wide will fit nicely on the forum web page. It is best to zoom into just the area of the image that you want to show and crop that section out while it is a high resolution image. After you have your section cropped, resize it to around 600 pixels to 700 pixels before posting it.Sometimes it is necessary to use a wider image for something like a schematic so I have gone up to 1200 pixels wide and I know someone viewing it will have to expand it to fully view everything. Most of the time I set my pictures to under 700 pixels in width.I hope that helps.-sonavor
My turn to ask a ''dumb'' question Lonnie,
A simplyfied diagram of 1R17, 1R18, 2R2 is a parallel set-up where R17 is parallel to R18 and 2R2, right ? And the same with 1R15, 1R16, 2R1?!!
I am not quite clear where , what and howyou want me to measure ?? I must be sitting on my brain :-):-)
I will look into that.......but did you get my reply to your suggested checks on the board ??
Also did a re-check on 0C3 & 4 - all fine !
My oscilloscope may? Not measure the un-amplified wien bridge signal - I could not detect a sine wave, not at C14 with or without the R27 trimmer on board........also tried a replacement bulb.......nothing !
There are only a finite number of components on that damn board:-):-)
Where can we possibly go from here ?? We have to rally the troops, one universal soldier may not win the match ?!!
I am not in a position right now to check my BG4002 Type 5503 but in a few weeks I will be able to put a working one on the bench and make some measures with a scope and DVM so you can compare. Hopefully something will come to light before then and you will solve it.
I think I got it:
Are you looking at a parallel set-up of 1R17 and 2R2 which would have to be smaller than the value of 2R2 ??
If 'no' than I don't understand
Sounds like a great idea John because right now I am sitting on a carousel !!!
Looking forward to our 'measuring comp', which has to deliver as I am not overly confident something jumps into my face before then !
Talk soon
If we concentrate on the 45 rpm circuit first, the top end of the Wien bridge is made up of 1R22 + 1R24 in parallel with 1R23 all in series with 1C11. The bottom end of the bridge is made up of 1R18 in series with 2R2 in parallel with 1R17 all in parallel with 1C9. To make sure the bottom end of the bridge is properly connected you can measure the resistance from 1R17 through PO across to 2R2 and back up to 1R18. If this is all connected the only resistance you should measure will be approx 2R2 which will be something less than 1K depending on where it is trimmed to. If the circuit is not complete you will measure the blue circuit which has a resistance of 1R17 + 1R18 which is a bit over 60k. The bottom end of the bridge is AC grounded back at 1C13 so you need to make sure this is also properly connected. You can measure that from the same point on 1R17 to the positive end of 1C13.
If you want the circuit to oscillate at 57.3 hz you would need the resistance in the top leg to be approx 5k9 which means you should try and set 1R24 to approx 1k9 ohms.
Sorry - 1R24 should be set to approx 1k4 ohms not 1k9.
Thanks for that Lonnie,
2R2 is set at center '0'.
I get about 540 Ohm, which changes when I operate 2R2 as expected.
I am however quietly but cautiously confident we are barking at the wrong tree ?
That said, I am not prepared to bet my life on it !
Great, the measurement was to confirm the wiring from the main board to the keyboard was all intact. So the bottom half of the bridge is intact. One thing to cross off.
Did you confirm the bottom end of the bridge is grounded?
Measuring from1R17- same position that delivered about 540 Ohm previously - to the 1C13 delivers 0.7 Ohm ?!!
Now, is this good or bad ?