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
Beogram 4000 major problem.
One of the major problems with Beogram 4000 is the high number og mechanical switches. Actual there are 17 mechanical switches in a Beogram 4000. These switches have always been a potential risk for a stable function over time even after a good cleaning and adjustment.
The reason is corrosion of the silver plating.
This photo shows the problem.
I have some time ago decided to solve this problem. I have found a Danish company accepting to work with very small quantities when re-plating the contacts. It is very expensive – mainly because of small quantities.
But we have now a solution for all the customers of Classic Audio.
This is the silver plated switches.
/Frede
A luxury solution.
I repaired one of those that was broken by cutting a new one one out of a sheet of thin brass
Jacques
I am curious on how expensive very expensive is. Looks great of course.
-sonavor
I do copper plating as a part of my daily work (industrial and big pieces) the problem is you have several work cycles that all can go wrong, first comes a good cleaning with acetone or an acid, then an electro cleaning, then clean with water, then an activator, and then depending on the to plate material, nickel plating and at last the copper, all this done at different voltages and Amperes depending on the size of the item, I have never done silver plating, but the procedure must be similar. The chemicals used are expensive, and for each step you will need a steel basin connect all the items to an anode and the basin to a catode, adjust your current and know the time to be used. Not easy, comes to it the safe destruction of the chemicals after use.
Collecting Vintage B&O is not a hobby, its a lifestyle.
Hi my begrime 4000 was working fine but then suddenly it stopped lowering, in not sure the most likely causes but is there a list of A-Z
for most likely trouble, it seems there is no activity from the solenoid, its not clicking, the on works fine, the tone arms cues but stops at the lead groove.
it also tracks across when there is no vinyl so it must be sensing no record, but stops at lead groove. up down does not activate it.
Please help
Check the solenoid current limit switch. The switch is closed when the tonearm is up (solenoid disengaged). After the solenoid engages and the lever moves forward this switch disconnects to limit the current to the solenoid. If that switch isn't closed at the start there may not be enough current to activate the solenoid so your tonearm won't lower. Worse case is the switch may have to be removed, cleaned and straightened. Before going that far you might only need to clean the contacts with some fine sand paper and check the switch position. Beolover has a discussion of this on his blog.
Hi Sonavor, thanks for the reply.
I did exactly as you said, had seen Beolover before and watched again, i used a little micro mesh to get to the points on the limiter switch, the switch itself is making contact, it is set as beolover described.
every other function works well it scans across when no record is on and and returns, then with the record it stops at the lead groove. The solenoid did not activate.
Any other ideas anyone?
The Beogram 4000 I am working on has a similar problem. I am in the process of trouble-shooting through the control logic to see why the solenoid isn't activating. My turntable logic has the additional problem of not stopping at the set down points even though I can measure that those 24/30 cm and 17 cm switches are sending a signal to the control logic board. In addition, my turntable also won't manually set down when I use the lowering button. I will let you know what I find.
hi again
Sounds like you have a lot more wrong with your BG 4000, the strange thing was mine was working away great but without and incident it just stopped lowering. I've taken the switches board out to finely sand between the points and put back together as believer had done, but no change in the current state of non play. Because mine is working well in all other areas surely it can't be much, it just seems like power is not activating to solenoid.
i would take the switches apart again if i thought it might be that, but I'm not sure after taking it apart already.
Literally everything else works except the solenoid activation, if this worked I'm sure the deck would be fine.
i have another pretty beaten up BG4000 and swap the solenoid from that around but still no change, so i ruled out solenoid being broken and my mate checked it and it seemed fine.
Thanks again
kevin
Check if one of the switches on the operator panel is permanently activated.F.eks. the UP switch.
Martin
Hi Dillen
do you mean the operator panel the silver square panel up down/ left right?
Also are you Dillon that you can get belts for systems such as cd 50 and also aluminium strips for Beogram 4002 lids?
Thanks
Kevin
Yes to the panel.Yes to belts.No to alu strips, that's Frede of Classic Audio.
Dillen: Yes to the panel.Yes to belts.No to alu strips, that's Frede of Classic Audio. Martin
Stripped the control panel and they points were very tarnished but the up and down etc cleaned and the switches were working fine.
I think i can rule out the control panel, i put it back together and all buttons seemed fine, just no action from solenoid.
I feel tempted to point to Sonavors thread.He is currently working on a Beogram 4000, he is very competent and doing things the right way.
hey Martin
I will have a search for that, is it just a case of going into his tab?
Hi john,
I have taken on a big challenge, just aquired a nice BG4000.......but.......
Getting through the fault-finding flow chart alone is not that trivial, for instance what means Q2 = high ?? What's high or low ?? And then there is the circuit diagram........used to find the disignated parts of the CD doing 'automatic lowering', 'detector arm sensitivity', etc is quite tricky.
But back to the trouble my BG4000 showed:
It powers on, carriage moves to the 30cm run-in groove and then stops.....without lowering ?
The carriage can moved with < or >, reaching the run-out groove but won't return after ES has been activated ???
The only way back is via the >- function.
At no stage can the solanoid be activated ???
I have fine-sanded all brass contacts, lubricated all nipple-witches - nothing supicious there .......
Have to admit with the fault-finding flow-chart alone I won't get anywhere without some assistance from one of your expertise......
Looking forward to an expert-reply
Cheers, ALf
Hi Alf,the Beogram 4000 is uses some early NAND IC devices in the control panel to manage the logic for the control signals. Those "Q" signals are derived by the BG4000 control panel NAND gates to control some of the transistor switching on the main board. For example the Ǭ₁ signal controls the tonearm solenoid by turning on/off the 1TR10 transistor. The "low" values are typically around zero volts and the "high" values are around 6 volts. But the function of those signals are Boolean, one value or another.I haven't had the exact same problems as you regarding the tonearm lowering but I did have a case where one of my BG4000 turntables was not lifting at the end. I verified the ES button was triggering but it didn't work correctly when the turntable was in operation playing a record. The problem turned out to be the metal bars that travel and press down the plastic button (nipple-witches you called them). The metal bar for the MV button was slightly higher than the others. It took readjusting those metal bars to get my Beogram working properly again.That can be the difficulty in getting these turntables back to perfect operation. A lot of mechanical adjustment and readjustment is necessary.Try running the turntable without the platter on so you can get measurement probes on the control signals. With the platter off the Beogram will think there is a record in place and try to set down and play. You will be able to check out the control signals involved for each state. Monitor the base of 1TR10 and/or the point between 1R25 and 3IC1 (Ǭ₁). See if the voltage of that signal ever changes. Ǭ₁ causes the tonearm solenoid to engage when Ǭ₁ goes low (zero volts). When it goes high enough to turn on 1TR10, the tonearm solenoid disengages. The OFF signal, ES signal and DS signals (that feed 3IC1) need to be at a logic high for Ǭ₁ to be able to go low.
John
Beware, if the detector arm bulb is open circuit, the deck will behave like this too. At least that is what mine did prior to bulb replacement.
Thank you kindly for your reply - what can I possibly say about your BG400x project post that has not
Yet been said ??!!
I only wish my 'expertise' would cover a fraction of it.........
Let me briefly recap - perhaps start with the 'good' things:
The BG powers on, the strobe-light is on, motor spins at 33rpm, < and > work fine, with the naked platter on the carriage moves right across with the arm raised and stops near the center from where it's supposed to automatically return...
With the platter off the arm moves to the 30cm run-in groove position, stops but.....
The 'bad' things:
It does not return, unless you activate the >-function at the run-off position to bring it home!
With the platter off the arm gets into the correct position but the arm won't lower - neither automatically nor manually , meaning the up or down function can be activated.
I measured some of the voltages at 0C1, 0C2 and 0C4 :
At 0C1 rectifier outpu for the 6V rail should be around 12V - I have 8.7V
At 0C2 regulated 6V-rail I have 6.1V
At 0C4 regulated 24V I have 22.6V.
I fine-sanded all brass-springs/contacts and they should work fine.
None of those nipple-switches ( not witches !!) Is/was permanently engaged.
The bulb in the detector-arm is on - no open circuit.
The voltage at the Base of 1TR10 does not change, no matter what I am trying to activate and is around 0.7V.
Oh yes, one more mal-function is the 'Off' function........no reaction whatsoever !
Well, this is where I stand and it looks as I am far out of my depth here unless first aid is administered.........
Still trying to work my way through the fault-finding chart........not as easy as it looks !
Anyhow, it is not all bad and my gut-feeling tells me this patient doesn't need to die, does he ?!!
Looking forward to all of your helpful coments :-)
Cheers
ALF
Sorry guys, just another typo....
It should read ' ....... meaning the up -and down function can NOT be activated! '
ALF: The voltage at the Base of 1TR10 does not change, no matter what I am trying to activate and is around 0.7V. Oh yes, one more mal-function is the 'Off' function........no reaction whatsoever !
The base at 1TR10 being 0.7V means it stays on and the Ǭ₁ signal is not getting generated by the control board. The following diagram from the service manual shows the signals involved on the tonearm lowering and the voltages I noted when I was working on my BG4000 turntables.Check the states of those signals at the point of your problem (the 25/30 switch point). If the four inputs : OFF, ES, DS and 3IC1 pin 8 don't all go High ( > 2 V ), Ǭ₁ will not go Low and cause the tonearm lowering solenoid to engage.
Ok,
Here is what I could measure with the arm at the 25/30 switch-point:
ES = 0.52V, OFF = 2.3V, DS = 4.6V, Pin8 at 3IC1 = 0.53V..........
As a side issue: almost all of those yellow 3.3nF cap were between 1.5-2.2nF on board 3 - measured
In circuit though !
Have you considered the option that one of the FCH131 chips is faulty ???
The fault-finding chart points to a few of those ICs on the control board - that would indicate those are not bullet-prove !!
So far I have not engaged in replacing the electrolyte caps yet but would cautiously guess that this
Will not impact on the problem at hand ?
BTW: how can you modify these diagrams so beautifully with colour ? Which program are you using ?
It appears that your ES signal is stuck in the activated position. With ES at 0.5V, the Ǭ₁ cannot be generated to activate the arm lowering solenoid. The low state of ES keeps Ǭ₁ always high. Run the Beogram with the platter off and the slide switch bar assembly removed (the assembly with the metal bars that press the nipples of the switches removed). That way you can manually operate the switches. When I was having problems with my Beogram logic I suspected the NAND chips (FCH131) but they are a really durable device and unlikely to fail. My issues all turned out to be mechanical. I would exhaust troubleshooting all of the switches involved first before suspecting the FCH131 device. For the schematic diagrams I either take a screen shot of the PDF page or scan the service manual page. Then I use Photoshop to edit the picture. For my work photos I use the camera on my phone and Photoshop to size the picture and add comments.John
Hi John,
Done that - that ES switch turns the carriage off but it does not return to its resting position ?!?!
All those nipple-switches work fine but the ES signal I am getting is still low ??
As a matter of precaution I even replaced 1TR10 to be on the safe side......no impact.
I ordered some of the FCH131 chips - they were quite difficult to buy at a reasonable price - just in case.
The solenoid is definitely not dead !!
Even a known reliable chip can sometimes fail,.......
So, the 2 remaining issues are still the arm lowering and the OFF function........
I need a rest mate......before 'beolove' gets into gear again......
Cheers - ALF
I wanted you to check the manual operation of the carriage switches in an attempt to stop the tonearm carriage and lower the tonearm. So you would need to manually activate the ON switch followed by the 25/30 or 17 switch, then check the state of Ǭ₁. Just focus on the lowering problem first. For the lowering problem - the signals going into 3IC1 (DS, ES, OFF) and its fan-in extensions (FR, SI, R, FF, L) should all be at a logic high voltage state. If any of those are low (less than 0.5V), Ǭ₁ will remain high and not send a signal to the solenoid control circuit. If ES is always measuring then that is a problem.If you want to put your mind at ease regarding the FCH131 IC then swap 3IC1 with 3IC5.
Done just that....
DS, ES, OFF are all > 0.5V
From BS, FR, SI, R, FF, L only SI, FF & L are >0.5V , the rest remains <0.5V
That - in your words - is a problem........ :-((
Earlier you said that you had OFF = 2.3V, DS = 4.6V at the 25/30 switch point. What happened?John
I revised the control panel diagram last night. The BS signal isn't part of the 3IC1 extended inputs.John
With the spring carrying metal plate off I started with 'ON' and stopped the carriage on its way by pressing the 25/30 nipple-switch as suggested by you.
To the measurements DS, ES, OFF and Pin8 at 3IC1:
DS = 4.3V at PC3 but 0.17V at PC1 ???
ES = 0.52V at PC3 but 1.4V at PC7 ???
OFF = 1.5V at PC3 - drops down to 0.6V when OFF is pressed.
Pin 8 at 3IC1 =0.54V
Unless I did something wrong this is what it is !
I was hoping you would just have one signal that was the source of your problems but your Beogram obviously has quite a few signals in unexpected states. I'm not following your designations : PC3, PC1, PC7. What points are those?Here is a screenshot of an Excel file I made back when I was measuring the Beogram 4000 control signals on my two turntables. It shows the signal name, where I made the measurement (on the control panel board) and the measurement values for various turntable events.
As per service manual:
PC1 = PRINTED CIRCUIT BOARD # 1
PC3 = PRINTED CIRCUIT BOARD # 3 (CONTROL PANEL)
PC7 = PRINTED CIRCUIT BOARD # 7 (SENSOR BOARD or nipple-switchboard)
Does that help in anyway ? Is it now more likely that perhaps one of the NAND-NOR chips is faulty?
I will attempt to take new measurements according to you table and see what I can reproduce or
Where my table differs.......
What a job that is :-)
I revisited the points at the control panel - 1st column of your measurements:
17 = 0.29V, 25/30 = 1.15V, 33' = 0.89V, 45 = 1.67V, BL = 4.5V !!!, BS = 4.5V !!!, DR = 4.5V !!!
DS = 4.5V !!!, ES = 1.38V !!!, FF = 1.7V, FR = 0.54V !!!!, L = 0.86V, OFF --, Q0 = 4.44V, Q1 = 4.4V
Q4 = 4.3V, S = 0.174V, S1 = 4.6V, WO = 4.5V
I have not yet done the remaining measurement cross-check !
I assume there is already a problem ???
If so, how bad is it ??
Cheers, ALF
It is hard to tell without actually having the machine in hand but it kind of looks like your power supply isn't able to supply the necessary voltages. On my first BG4000 unit I had to have a replacement transformer built because the original one was bad. When I had to have my replacement built Martin and Frede told me that they have seen a number of those BG4000 transformers start to fail. So it is not uncommon for such a thing to happen.
That doesn't sound very good !!
So, let me get this right:
we basically can rule-out a NAND NOR Chip failure ?!!
We would not achieve anything by replacing the big cap-reservoir ?!
Is the an easy way to check the transformer ? In one of my previous replies I measured
The 6V / 12V / 24V rails !!!
Not quite sure about the next sensible step ???
PS: how much did it cost you to get a transformer replacement ??
I am not ruling out ruling out anything yet. Did you monitor the rail voltages with the Beogram under load? Check what the 6V supply is when you are operating the Beogram operations to see if it varies as the Beogram is in use. The best way to test the transformer is installed in the Beogram (under load).
A replacement transformer can be expensive - between $200 and $300 USD. That is because you won't find a ready-made, off the shelf replacement. You have to have one made custom to fit into the Beogram 4000 space. The old original transformer can't be repaired either because it is packed in epoxy. Opening it up will damage it.
On my first Beogram 4000 turntable, before I had a transformer made, I used a bench power supply to provide power to the Beogram and verify the turntable functioned okay with good power. If you have a good bench power supply you could rig up power to the turntable (bypassing the BG4000 power supply) and verify if the rest of the Beogram circuitry works. That is a not a quick operation but might be worth it to find out for sure if your power is good.
Very well........ but forgive a few 'naive' questions:
Where is the platter-and carriage motor getting their required voltage from ?? Can that come from faulty transformer considering both are working well !??
Why wouldn't be there enough voltage for the carriage-return at ES if it works forward via '<‘ ?
Same as the OFF function as '>‘ works fine ?
I tried to measure on PCB2 the +6 and +24 V (next to the reed relay) but there doesn't seem to be much
more than 0.2.......V ??
I begin to wonder if there is a faulty component on PCB2 rather than a faulty transformer ??
Sorry about my second-guessing, however still hopeful the problem can be cracked...........
There very well could be a problem on the power board. From your measurements I was suspicious of the power so a faulty transformer is just one of the possibilities. However, I would not recommend changing the transformer without fully checking out the system power, such as using a bench power supply. I think your next step now should be to re-measure the main power supply voltages again and record where the measurement point is and what the voltage value is. You will need to do that for the off and on state. Just be careful and connect your measurement probes with the Beogram unplugged so nothing accidently gets shorted. It is too easy for a probe to slip so unplug the Beogram when moving the probes as well.