[hcraig244]

Be very careful when removing or installing the cartridge, the plastic connector will be very brittle and susceptible to fracture, many have suffered this fate. As Mark says it looks very much like the cartridge isnt seated correctly on the grounding tab (copper spring that grounds and also helps keep the cartridge in place) make sure the slot at the bottom of the cartridge is free of any debris. These arms can be repaired however its a fraught excercise that requires a degree of destruction prior to rebuild, and of course purchase of custom 3d printed parts, available from Rudi at a cost….dont bend the copper spring, is meant to be shaped to fit….there is a distict “click” when the cartridge is fitted correctly.

This is one i repaired with a 3d print and self fabricated spring…

Should fit like this…..hopefully you only need to align yours correctly and it will ir snug

Good luck

Craig

[hcraig244]

I have been involved in a good number of BG4000 repairs/restorations over the last 10 years or so…..the two in my possession where purchased as spares or repair over 7 years ago for around £150.  I spent perhaps £60-£100 on parts, components etc on each…and in one case many hours chasing down an intermittent fault that ate my lunch for weeks….I also relied on the expanse of knowledge and support from the members on this site. I now see, as everyone else on the site, the same decks offered….and in some cases sold, for eye watering prices. I actually think the decks are worth these sums once repaired and fully functioning, the 4000 is massively over engineered and the means by which the end has been achieved by B&O looks to be the most complex and complicated procedure imaginable given the technology of the day…. to introduce a deck of the same quality and engineering excellence into todays markets would be prohibitive, as can be seen by the price tag placed on the 4000C upgrades offered  currently……..for some of us its not an investment/earning opportunity its more a passion for quality.

Personally I prefer the 4000 series over the 4002 due to the inherent complexity of the machine, this does however bring with it the regular hiccup’s associated with such old equipment….which most of us actually enjoy resolving…for me you should consider your motivations before shelling out £1,700 for a potential return down the road.

Craig

 

 

[hcraig244]

Post a couple of pictures…..may help diagnose the problem for you

Craig

 

[hcraig244]

This is where a signal generator and oscilloscope come in real useful, you can track the signal path through the circuit until you pick up the distortion…….not much help I know 😳

[hcraig244]

you may be lucky and only have to replace the lamp in the end of the sensor arm……good luck

Craig

[hcraig244]

check out beolovers blog on this…..may help you understand whats going on

https://beolover.blogspot.com/2022/05/beogram-Replacing-sensor-arm-bulb-with-led.html

[hcraig244]

did you change the tuning indicator lamps in the tuning circuit? if so these must be replaced by lamps of the exact current pull….i had an issue with some i changed on a 4400, Dillen provided the correct lamps and all was well.

Craig

[hcraig244]

hcraig244 wrote:

Also bear in mind that some components can measure up fine when tested, but fail under load…..I’ve had this issue in the past, and replacement parts from suspect suppliers should be avoided…early transistors can still be found as old stock and are a safer bet than ebay

Craig

hehe…..

[hcraig244]

I’ve had a similar problem in the past and with the help of a signal generator and an oscilloscope traced it to a noisy transistor in the pre-amp section as I recall….I’ll take a look at the circuit diagram and see if I can remember which one it was. There will be a post by myself in the archives detailing this im sure 🤔

[hcraig244]

It’s tricky…

You dont need to remove the front panel, thank goodness…..would be a shocking design defect if one did. The lamp is held in a holder that slides into the side of the moving coil meter, the holder has two wires soldered to it to illuminate the lamp therein. the meter also has two wires soldered on to it externally to power the moving coil, cant remember if its a moving coil or moving iron meter…..non the less it has two wires!

The meter is held in place on the front panel by a copper leaf spring which in turn is held in place by a single screw, see below. when this screw is removed the meter will push in from the front of the switch panel and be sort of accessible, the connecting wires are single strand and very unforgiving….the tugging and pulling required to remove the lamp holder in situ with all wires still connected is traumatic and in one case for me I broke a connection to the moving coil and had to replace the whole thing….fortunately Dillen from this site had a used one he let me have ;¬)

My approach of choice now is to snip the four wires that connect to the meter, well inside the unit for ease of re-soldering later, then undo the screw and spring thus allowing the meter to be removed from the underneath of the chassis, the lamp holder can then be slid out and a new lamp inserted and the meter re installed prior to re soldering the snipped wires. This is a very delicate operation, partly due to the frailty of the connections and getting the spring loaded screw back in place is also a challenge best done before soldering the wires back in place. You also need to replace the lamp with one with the correct ratings…Dillen can provide the correct one.

 

• This reply was modified 3 weeks ago by hcraig244.

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[hcraig244]

I have found a number of these random intermittent faults have been caused by the switches feeding the logic gates within the control panel, the logic chips are very reliable and seldom, if ever fail….the switches feeding the gates however are very susceptible to fail…typically arc and corrosion, and also bending over time…if a leaf type switch is left stood in one position for a long time it will loose some of its elasticity. The switch that controls the lower current to the magnetic coil is one such switch, if this is not clean and fully functional it could cause the issue you describe, also clean and inspect the control panel switches….have a read of the training notes donated by Solderon in the manuals section of the products area…..they are very informative.

Good luck!

[hcraig244]

When you say it only happens in the first 1/3 of the record does it always happen at the same point each time it occurs?

[hcraig244]

good work….sounds like the red herring thrown up by the DBT is resolved, regarding zapping something if you power up I suspect the offending component will have been zapped sometime ago when the problem first arose, again if you have a variac (very useful for fault finding) try disconnecting the 15v supply from the circuit somewhere around halfway through and power up the 240v slowly monitoring the current pull (put your DVM in series) as you do so…..if the current starts to go up alarmingly the fault is in the part of the circuit connected…..check all components

Good luck

• This reply was modified 1 month, 1 week ago by hcraig244.

[hcraig244]

One other thing…..the circuit diagram shows 22vac from the transormer to the 15vdc rectifier…..your measuring 17.6vac

made a proper bollocks of the images i know ;¬)

• This reply was modified 1 month, 2 weeks ago by hcraig244.
• This reply was modified 1 month, 2 weeks ago by hcraig244.
• This reply was modified 1 month, 2 weeks ago by hcraig244.

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[hcraig244]

you have replaced or proved every component in the circuit, confirmed every track and solder joint all to no avail….the only outstanding item is your transformer….do you have a variac you could power the 15v rectifier from?……you have eliminated every other component in what is a basic power supply circuit….i keep thinking of the fact that the circuit performs correctly on power down….back emf from the transformer, if that’s even possible, could be doing this……there isn’t anything else to check ;¬)

Craig

[hcraig244]

could that brief spike be back emf from the transformer when it shuts down….i have to agree this isnt making much sense, you have changed the smoothing cap and bridge rectifier…cap is in the correct polarity, have you powered up without the DBT on the supply?

Craig

[hcraig244]

Sounds like some progress…..change TR17 out and you should be good to go for the FM issue, dillen from the site always advocates the “half it” approach which is to go half way into the circuit and disconnect/test then work back or forth from that position…..always works for me ;¬)

Craig

[hcraig244]

Hi

just seen your post, this can most likely be repaired, see my post in the forums for Beovox for the procedure

hcraig

[hcraig244]

this?

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[hcraig244]

Not quite sure what your describing here….do you mean the tone arm?….or something else?

Craig

 

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