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
Drove down to Manchester yesterday to do some Christmas shopping, and picked this up while I was there...ebay again, need to get a handle on this ;¬)
Chap who sold it to me, very nice man actually, said it has problems..."turns on, platter spins nothing else happens, driving the carriage assembly right and left works but arm doesn't lower at any point" so this could be fun! cosmetically is not all bad news, control panel looks in very good shape...
The wood trim is still looking good too, nice sharp corners, although the platter looks like someone has been throwing pots on it ;¬)
Popped the stylus out....still has a point by the looks but also looks very dirty, what is the best method of cleaning these?
The pic I forgot to include....
Well that's the good news....bad news is the aluminium tape along the top.....I don't think this can be saved.
Will give it a go of course....
The trim panel does look a bit rough - I wonder if Frede can be of assistance again? Cleaning the stylus is best done carefully!! A magic eraser sponge is very useful - simply dab the stylus in it - up and down - not dragging obviously. If you need more, an alcohol cleaner can help but be very careful that the liquid does not run up the cantilever. Many of these cartridges will have seen better days - have a good look at it when clean - a test record can also be used to see if the suspension is ok.
Peter
Which cartridge is it? The 4000 was fitted with an SP15 originally - these were the first of the B&O cartridges without a replaceable stylus and when it was worn, B&O would sell you a new one at half price - the offer is no longer valid!
This was replaced by the MMC4000 in later models and then by the MMC20EN in the 4002.
https://www.classic-audio.dk/content/classic.php?page=dustcover
Milton
Frede had a lid made for my BG3000 Thorens with 12" arm - I had made one previously and had sent him one - his were better as slightly thicker perspex. The replacement doesn't have the trim strip in the picture though.
The platter will be an issue as it has corroded and this will not simply clean off. The platter of the 4000 is more complex than that of the later decks as it is much heavier and has the strobe on it. Don't know of an obvious fix.
Thanks Milton
Looks like Frede may be able to help, will drop him a line.....and Peter yes the stylus is SP15, looks very dirty, looks sort of furry along the stem
poor pic....needs to be clicked to view it
Ok....powered up and was greeted with a platter that rotates but a pickup arm that remains stationary, the dial indicator lamps are glowing as is the 45rpm indicator lamp. The pickup arm can be driven forwards and backwards manually but that is the extent to the units function. Following the fault finding road map ON with no record turntable runs, does turntable run @ 33rpm No its running at 45rpm, suggests Q4=high yes or no, when I measure at this point in the logic I'm reading 0.4vdc or there abouts, to me this sounds like a low but I'm not sure what voltage level represents high. taking it as a low indicates a check for 24vdc at the collector of 1TR6 which is a No, I can hear the reed relay clicking when I operate the selector from 45 to 33, the platter speed reduces and the rpm indicator lamps change over to 33rpm, however when I let go of the 33rpm switch it reverts back to 45rpm and the 45rpm lamp is illuminated. This all suggests the relay is working, the road map says replace 1TR5, 1TR6...…...does this sound about right?
Craig
When you get to it, I am sure I have a better cartridge you can have - I have never seen a cantilever look like that!!
Pretty special eh! looks like it has been wrapped in some sort of insulation....or growth has started to take hold.....
Ok.....been a little distracted painting the kitchen walls, little guidance required here, the road map leads me to suspect 3IC4....but for clarity I need to be sure that the High level im getting is really high. I'm measuring 4.8vdc as a high (however some of the measurements that may be high are only around 2.9vdc) and the low measurements are around 0.04vdc......
Also ann anyone confirm this odd symbol is 3IC6 output?
This is what I think is the measuring point of the odd symbol, looks a bit like an inverted infinity symbol to me
Hi Craig,
the symbol is probably the greek charachter for 'gamma', the third letter in the greek alphabet.
The used logic family in the Beogram 4000 is 'low-speed logic'. Those chips were produced by Siemens. They accept < 1V as 'Low' and about > 2V as 'High'.
I don't know the beogram 4000 but in the service manual there is a 'Auto speed sensing' mentioned. In the failure flow chart you added a comment about the speed switching from 45 -> 33 rpm and fallback if you release the button '33'. I would say that this is a correct function if i assume the mentioned 'Auto speed sensing' works as designed. Also if i assume that this function is correct and follow the failure flowchart it should give a way to the failing component because the speed will be changed manual. So you should come directly to 'Y' branch of the decision ('Is SI missing Low IMP') and not to the 'N' branch.
In every case should one of the chips be defect you can order all at 'little diode'
Good luck with this nice icon from the seventies!
Ralph-Marcus
Ralph....I'm tending to agree in so much as the speed will change when the 33rpm switch is made and returns to 45rpm when released, this does suggest that the logic gates are in fact flip flopping 😉 Just seems like it's starting out on the wrong foot. I have also noticed that before pressing ON I can press the 45rpm switch and the platter spins at 45rpm, which is correct....however pressing the 33rpm switch does nothing...something fundamentally wrong with this 33rpm circuit, reed relay next under the spotlight..I have ordered some chips just in case.
Took a look at the "SI missing low IMP" cause and measuring at 1TR20 found this pulse signal at the collector of TR20 which provides said signal to the logic gates.....looks fine to me, well its a pulse though not so sure its 10ms.
still not convinced about the NAND gates but awaiting delivery of replacements so....had a look beyond the 33rpm issue. I have found that if I replace the platter and drop a 33 disc onto it and manually drive the tone arm into place I can manually pull in the solenoid and the tone arm drops nicely into the first grooves and the tone arm drive starts to jog along nicely, good to find something that works!
After measuring the inputs to 3IC4 several times and confirming that all the inputs and outputs where as per the logic diagram still the flip flop refused to latch when 33rpm switch was made.....activating the 33rpm switch puts a "1" into the 45rpm gate which in turn puts a "0" into the 33rpm gate therefore holding it HIGH or latching it until the 45rpm switch is activated again reversing the outputs. My replacement IC's came today so I replaced 3IC4 and was rewarded with the ability to manually switch from 45rpm to 33rpm with the selection of 33 rpm latching.....
I was expecting the platter to start up in 33rpm mode, that I can select 33rpm now is good but not what I was expecting. The tone arm still sits tight and refuses to move so there is still a long way to go, the fault finding road map leads me to replacing 3IC0 or its capacitor 3C12....that's a task for tomorrow.
Check the V6 supply.A problem with the regulator or the zener can cause it to run high, and that typically causes problems in several circuits.The regulator runs warm. I like to place it on a small cooling fin outside the board - near the two filter capacitors for ease of wiring.
Martin
Found this on Ebog......https://www.ebay.co.uk/itm/NEW-Bang-Olufsen-Beogram-4002-dust-cover-B-O-NOS/323547226820?hash=item4b54eae2c4:g:WXkAAOSw~rhb6jpg
Maybe some help.
Keith
Keith : Found this on Ebog......https://www.ebay.co.uk/itm/NEW-Bang-Olufsen-Beogram-4002-dust-cover-B-O-NOS/323547226820?hash=item4b54eae2c4:g:WXkAAOSw~rhb6jpg Maybe some help. Keith
Thanks for that info....dont know if a 4002 lid would be compatible with a 4000 unit ;¬)
Thank you for the advice, will varify the voltage level is stable... though I suspect this is something I should be doing anyway, do you have a picture of this modification?
Ok....checked to 6vdc at 2TR6 and its fairly stable at 6.8vdc...the Zener is set at this value, 2TR6 does indeed run quite hot however. Having done nothing more than confirm voltages around 3IC0, to see if it was switching, the pickup arm has mysteriously started to move across, this now occurs everytime I switch the unit on....it still starts at 45rpm but the pickup is now moving, it doesn't travel out when ES is reached...but that's a problem for tomorrow.....
Having given this some thought and taking into consideration how flakey everything seems to be, One time on start up the machine set off at 33rpm, the pickup arm moved in and stopped at the first groove of a 33 album....but didnt drop, I havent been able to replicate this and it mostly starts as described above. So....in order to bring some order to the task I will dismantle all the mechanical switches....gold plate them and check the continuity from each one, this will give me the confidence to eliminate these signals from the fault finding process.
And replace the regulator transistor. They go weak, allowing the voltage to jump up and down with varying loads.I have no photos of the modification, but it's merely a matter of fitting a transistor to a small piece of board, fit a small cooling fin tothe transistor (I use the type found on Beomaster 3000/4000 driver transistors or voltage regulators) and secure it all tothe chassis bottom (insulated).Two of the transistors connections (emitter and collector) are already found on the filter capacitors near by.The remaining connection (base) is just made as a lead pulled with the other leads and fitted to the board where the transistor sat.This takes a lot of heat away from the small board and also from the transistor itself, which has no effective cooling originally.It clears many problems regarding instability.
Thanks for that...I will replace the zener diode too while I'm in there ;¬)
Would you like to borrow mine as a comparison?
That would be very usefull…………..
Made a start on the slider switches.....don't look too bad to be fair.
Until I spotted this......looks like its been getting hot at some point, still measures up at 8.2 ohms however. not a very clear pic I'm afraid......
Scorched the board too...…..
Need to order a new 1 watt 8.2ohm resistor. The contacts don't look bad, they where quite bent but did look like they where making contact. Before gold plating.