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
Just make sure, you wire it up correctly (as per your diagram above). The current must flow in the same direction in both primary windings or else you're creating a magnetic short circuit. It's probably best to keep at least one 0.25A fuse in the supply line...just in case...
Ok.....wired up as per the diagram above, connected RD & BK and fed 240vac into GN and YW....WHT was left floating....and using the variac injected 240vac whilst carefully monitoring the current......the transformer pulled very little current as one would expect at idle
Happy with this I next confirmed I was delivering 240vac into the primary windings....
Moving onto the secondary windings and unfortunately I'm still low on the neon lamp supply...
The 24v feed looks good........
As does the 6v feed........
As a final word I checked the secondary winding output to the neon lamp on my working deck and as suspected im getting 230vac........
Thanks! That leaves no doubt: at some point in time the 220V coil was overloaded and that caused a meltdown of the transformer wire insulation. That also explains the difference in resistance compared to your working unit.
So the 8V and 24V secondary windings are fine but the 220V winding is spoilt. A repair is probably not possible, at least not in a cost-effective way.I'm not really sure what this neon lamp 0IL3 does in this machine, but sonavor suggested that it's the strobe lamp for speed control.
You have two options: either you replace the neon strobe with a LED version or you get a low-cost, low-power transformer to replace that 220V winding.240V/240V insulation transformers do exist but they are usually costly and bulky and hard to come by, thus don't make much sense. I'd probably go for a cheap low-power PCB transformer. Reichelt is one of those low-cost electronics suppliers in Europe and <here> you can find a 5VA transformer for some 3-4 Euros that'll do the job just fine.The 27k resistor in the neon lamp circuit shows that you can expect a load of less than 10mA on the 220V side, which gives a maximum of 100mA on the 24V side. I don't know the wire gauge or load on the 24V side of your current transformer, but I think it should be able to take some extra milliamps - the circuit shows a 400mA slow blow fuse on the 24V output winding and you can assume that the normal nominal current on that winding is well below 400mA.
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postscript:
I did some more thinking this morning and I asked myself: What's actually the point of isolating the neon lamp supply from mains??
Answer to self: No point whatsoever! If you're not planning to move across the pond and take the BG4000 with you, there is no real technical reason why you can't connect this lamp to the primary! I guess the main reason for adding this 220V winding was to make it compatible with the US market. If the grid supplies only 120V then, of course, you need to step up the grid voltage to drive a 220V neon lamp.
Bottom line: the best and most cost effective solution for you is to simply wire this strobe lamp to the primary of the transformer and all is good!You won't have to worry about getting a replacement transformer or any add-on components. Just make sure that the wiring of the strobe lamp is in good condition and that there's no danger of any part of that circuit shorting out to the chassis.
Craig: Craig: I've just had an epiphany, or as some may say "a lightbulb moment" regarding the strobe lamp.....can anyone come up with a reason why I cannot connect across the 240vac incoming supply fuses through the reed relay and then into the strobe lamp? I seem to recall something about back EMF generated when disconnecting a coil i.e. an ignition coil on a car engine....could this be an issue bearing in mind the reed relay would open when the set is switched off?.........any thoughts would be welcome well....so much for that bright idea, tried it out and it didn't work......when I connected the neon lamp to the incoming fuses I found that the voltage dropped to around 106vac when the transformer was powered up, well below what's required for the neon lamp. I tried measuring the voltage at the fuses on a working unit and found the same reading........could a faulty bridge rectifier be responsible for this loss of 240vac on the secondary side (Martin.....I'm looking at you)
Craig: I've just had an epiphany, or as some may say "a lightbulb moment" regarding the strobe lamp.....can anyone come up with a reason why I cannot connect across the 240vac incoming supply fuses through the reed relay and then into the strobe lamp? I seem to recall something about back EMF generated when disconnecting a coil i.e. an ignition coil on a car engine....could this be an issue bearing in mind the reed relay would open when the set is switched off?.........any thoughts would be welcome
I've just had an epiphany, or as some may say "a lightbulb moment" regarding the strobe lamp.....can anyone come up with a reason why I cannot connect across the 240vac incoming supply fuses through the reed relay and then into the strobe lamp? I seem to recall something about back EMF generated when disconnecting a coil i.e. an ignition coil on a car engine....could this be an issue bearing in mind the reed relay would open when the set is switched off?.........any thoughts would be welcome
well....so much for that bright idea, tried it out and it didn't work......when I connected the neon lamp to the incoming fuses I found that the voltage dropped to around 106vac when the transformer was powered up, well below what's required for the neon lamp. I tried measuring the voltage at the fuses on a working unit and found the same reading........could a faulty bridge rectifier be responsible for this loss of 240vac on the secondary side (Martin.....I'm looking at you)
Manly
I tried that, when i measured across the fuses i got the volts drop described above.....
manfy
Another thought just struck me.....when I made the above measurement I was under the impression that the service manual circuit diagram was correct....
Now I read the whole thread from the beginning and things are starting to get clearer. Sorry, I should have done that before posting my first answer!
There's one post that doesn't add up, though:
Something must have gone very wrong in that measurement - it's physically not possible to see what you're describing here!The circuit diagram shows that 0R2 isa 27k 1/2Watt resistor, so the max current it can bear without burning up is 4.3mA and a 4.3mA load cannot pull down your mains voltage from 235VAC to 106VAC. Even if the neon lamp were shorted, you'd get a maximum of 235VAC/27k ohm = 8.2mA. If that happened the resistor would go up in smoke because it would have to dissipate good 2 Watts, but again you surely wouldn't see any dip in the mains voltage!
You can easily test the function of your neon lamps by connecting a 27k resitor in series with the lamp and then hook it up to your variac and turn it up to the nominal 220VAC. I didn't find any datasheet for the GL90 neon lamp on the net, but on digikey I found some modern miniature neon lamps and most 220V versions show an ignition voltage of around 180V +/-20% and a running voltage of around 80-100V. The lifetime of such modern lamps is usually spec'ed with 12000 to 25000 hours.
Craig: manfy Another thought just struck me.....when I made the above measurement I was under the impression that the service manual circuit diagram was correct....
Good thinking!
If the first image on page 6 is the actual correct diagram, then you connected the lamp only across the first primary winding, and that is less than half the mains voltage!Test the lamps you have with your variac as described above. Then you know for certain which one is working and which one is not.Also take note of the actual ignition voltage. That way you can assess the expected lifetime of each lamp. Ignition voltage keeps rising over the course of its life and when it's getting close to the line voltage (235VAC in your case), end of life is near.
Will confirm this evening as per the drawing below
Little later than I anticipated the transformer is back in the deck, all wired up with the 230vac incoming supply, correctly wired up this time, fed through the reed switch and 27k resistor
how about that..........
Craig: how about that..........
Applause
Collecting Vintage B&O is not a hobby, its a lifestyle.
Well done Craig! ☺️ 👍🏻
Jacques
These turntables can be so entertaining......seems like I learn something new every time a look inside one, and the input form the site is priceless
That saga complete its time to start replacing the trimmers and capacitors...........
Congrats on your successful fix!
If it were my machine, I would have checked the lamp current...just for peace of mind, you know! After all you have a damaged trafo coil and the only component that could have caused this is the lamp...That's just food for thought and I don't want to alarm you, but if the lamp for some reason draws more current than it should, it will shorten its lifetime and it may overheat the 27k resistor. If I understand this correctly, the light is permanently on whenever the platter is turning and you connected it now to mains voltage instead of the 220V that the circuit was designed for. Neon lamps don't necessarily have a linear V/I characteristic!
Thanks for that Manfy....however bear in mind the neon lamp currently installed is not the one that the machine arrived with...it's one of mine from a working machine, A new one will be fitted when it is delivered, actually I will test the new one out with my variac just to find the ignition voltage and compare it with one of mine. The 230vac that is now wired to the lamp is wired downstream of the fuse so we have that protection....I dont think there is any cause for concern.....unless anyone can advise differently of course
Regards Craig
Craig: ....I dont think there is any cause for concern.....unless anyone can advise differently of course
....I dont think there is any cause for concern.....unless anyone can advise differently of course
Hi, Craig! Yes, that's alright. There's no immediate danger in running the lamp temporarily at higher than normal currents - in worst case it would just burn out faster than normal. Unfortunately we don't even know what the specified max current of this GL90 neon lamp is because no datasheet can be found on the net. We can only assume, based on the B&O original design, that the current should be well below 4.3mA. If the actual current does get dangerously close to that value, you can lower it by connecting this circuit to the yellow and white wire on the trafo primary, which will give you <=220V instead of the 235V mains voltage between yellow and green.
Ok....this arrived in the post today, time to get a bit of a shake on......
As my working deck still had the wiring from the transformer disconnected I thought I would tie in my variac and (with the deck switched on to close the reed switch) I tried each neon lamp in turn to determine the ignition voltage, my original neon first, coming in at 163vac
And now the neon lamp I received today........which is igniting at a somewhat higher voltage, I think what Manfy was saying was that the ignition voltage got higher with age.....doesnt look that way? however.....now we have two working lamps ;¬)
The lamp issue finally resolved I will complete the capacitor replacement.............
Craig: And now the neon lamp I received today........which is igniting at a somewhat higher voltage, I think what Manfy was saying was that the ignition voltage got higher with age.....doesnt look that way? however.....now we have two working lamps ;¬)
Yes, the ignition voltage keeps rising over the lifetime of a neon lamp; that's the consensus in engineering textbooks -- but it is not the only failure mode of a neon lamp. In an older online textbook (from the early 70s) I read also that you might see a fairly big variance in those values even when you're looking at two lamps from the same maker with the same model number.
<Here> I found some general and interesting info on neon lamps with following statement:
"[...] Neon lamps gradually decline in light output as electrodes evaporate and condense on the inside of the glass envelope. This situation is gradual with failure defined as a 50% decrease from the original brightness. As neon lamps age, the firing voltages slowly increase until reaching the value of the supply voltage. At this point the lamp flickers and becomes erratic, indicating the end of useful lifetime.
Life expectancy of a neon lamp increases considerably as operating current is decreased. [...]"
Just a few tantalums to replace and start to reassemble the machine for a test run.......
time for a test run......all runs well, however......only getting audio from one channel ;¬(
The good news is that the cartridge plays fine on my working machine, so its looking like a poor/bad connection somewhere....the 5 pin DIN audio output connector looks a likely candidate
Bad news.....continuity exists from the DIN plug back to the connections within the unit, so although the plug looks a little tired its all good. Measuring from the connections back to the tone arm I have continuity from the red wire back to the second from left connector strip on the tone arm, great. I also have continuity from the white wire back to the third from left connector strip on the tone arm....also great, I have continuity from the blue/green wires back to the right hand side connector strip on the tone arm.....however there is nothing between blue/green wires to the left connector strip....open circuit.
Unfortunately continuity exists from all terminals to the solder connections to the rear of the tone arm
And on de soldering the blue wire from the rear connector of the tone arm I have no continuity from the left connector strip front of tone arm and the blue wire.....so its pretty conclusive that the break is in the worst possible place......
This can be repaired but it involves boiling water and a good chance of destroying the tone arm cartridge connector...........
Good amp choice Craig.
Craig: This can be repaired but it involves boiling water and a good chance of destroying the tone arm cartridge connector...........
I think Sonavor made some repairs on the cartridge connector, hope he chimes in here, good luck with it.
Hi Craig. I think you have no choice but to pull out the cartridge connector (via the boiling water method). Note: Just to give credit where credit is due...I learned that trick from Martin way back when I had to repair the phono connector on my first BG4000) :-)If the connector is good then a wire must have come loose so you will have to pull the connector to re-attach it. You should be able to extract the phono connector without damaging it. Just take care in pushing it out (after the metal tonearm assembly is heated via the boiling water). If the connector is broken internally it will have to be pulled and a replacement installed (a Beolover part will do the trick).Just in case someone wants to try to heat up and remove the connector using a heat gun instead of boiling water...don't. A heat gun will ramp up the heat too fast and is too difficult to control. You will risk permanently damaging the plastic connector. Then you will really be in a bind.Stick to the boiling water technique and if you find the original glue extra stubborn cycle the arm assembly between boiling water and ice water.John
Having discussed this with Justin the decision has been made to give it a go.....i have done this before but the connector proved difficult to get out, ended up buying a laser printed part from rudi......
Ok.....boiling water at the ready
After a couple or three cycles of boiling water/freezer i was able to push the mount out of the arm....however it came out in slightly more pieces than I would have liked....