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Justin's BG4000

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Craig
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Craig posted on Tue, Apr 6 2021 12:50 PM

Taking Sonavors advice Justin (Bulldog) asked if I would take a look at this.......I cant resist a challenge and I'm not doing much just now so have agreed to take it on..... when I say "me" I mean the forum of course ;¬)

 


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Craig
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It comes with a couple of kits from Rudi.......Capacitors and laser printed bracket along with two sets of LED conversions for the control panel

 


Craig
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Along with a list of issues as follows:

* only playing in one channel right now
* from time to time tracking arm drops before it reaches the platter
* sometimes starts in 45rpm automatically even when 12” is on the platter
* drive belt rubs agains the guides making noise
* low level hum from unit
someone has changed out a couple of capacitors already 

Craig
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Using the variac powered the unit up.......pulled very little current

 


Craig
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running at 33rpm with no platter or drive belt I cannot hear any low humming noise, everything seems to be operating within pre defined parameters.....as I have a a couple of drive belts spare I tried one and run it back up.......no rubbing against the guides either.


Craig
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There is a little scorching on the fuse sleeve of the power supply PCB...I've seen this before, the only real issue I can find is there is very little damping on the pickup arm....it drops onto the disk with an alarming clatter....and when playing a 45 disk it misses the start altogether and falls short, fortunately the pickup adjustment is good and the stylus doesn't hit the platter ribs. I have yet to check out if both left and right signals are present, I will look into that next...Its looking like a good clean of all the switches will sort out a lot of the intermittent issues.   

 


Beosince98
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Craig:

running at 33rpm with no platter or drive belt I cannot hear any low humming noise, everything seems to be operating within pre defined parameters.....as I have a a couple of drive belts spare I tried one and run it back up.......no rubbing against the guides either.

Thank you for sharing Craig. I myself have a low humming noise in my Beogram after I had a little accident when restoring it where two pins touched on the power PCB and created a nice black mark. I replaced the 6,8V Zener which was gone and the Beogram worked perfectly again, except for the low hum it produces now. Quite interestingly I can feel the motor move ever so slightly when I connect the Beogram to power and place my hand on it, so that hints at what parts I should check out and possible replace. Unfortunately I don’t have a oscilloscope to check the motor voltages. It is always interesting to read up on other people’s restorations, especially from someone experienced like yourself.
Craig
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Regarding Justin's report of only receiving a single channel from his unit I have checked continuity from the 5 pin din plug back to the pick up arm, had to operate the solenoid manually to this due to the grounding of ths output signals when the solenoid is de energised.....to my surprise I found this inside the pick up.....not seen this arrangement before.....my previous repairs have involved individual wires from the entry point to the stylus connector?

The continuity from the 5 pin din to the brass tracers on the underside of the connector shown is good....I'm suspecting a poor connection on the female side of this arrangement deep inside the pick up arm.

 


Craig
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Having cleaned and re assembled the pick up arm I have proved the continuity from the 5 pin DIN through to the stylus connector on the end of the pick up arm.....so I did what I should have done at the beginning and tried the stylus on one of my 4000's and it performed flawlessly.....


Craig
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A little befuddled I turned my attention to the 5 pin DIN plug, the clear wire loops perilously close to being proud of the plastic pin mounting assembly, making me think that when assembled the wire may be touching the outer case thus sending the signal to ground.....diffucult to get a good picture of it.

 


Craig
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This said I went ahead and replaced the stylus back into the pick up arm and with the 5 pin DIN cover still removed hooked the deck up to my Beolab and gave it a go.....I was rewarded with both channels operational, however the hum reported by Justin accompanied the output to the amp, grounding issue.....


Craig
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So...I have insulated the suspect terminals within the 5 pin DIN plug and re assembled it, soldered a link to connect the signal ground and system ground together and had another go...works perfectly now with no hum and both channels functional...I'm very happy the hum wasn't down to the transformer. Let it run for half an album and I'm thinking once I have sorted the pick up arm damping I will be ready to start replacing the aging components.

Martin

Do you have a kit for the 4000....caps and trimmers etc to include new belts? I think the belt rubbing on the guides was probably down to the wrong drive belt fitted (too long). Justin has sent me a kit for the big capacitors so I dont require those.  

 


Craig
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Moving on to the tone arm damper I have dismantled the assembly and discovered there is no adjustment on the valve that controls the flow of air into the cylinder.....the adjuster screw is screwed all the way in and wont come out.....someone has had a pop at this in the past, thought it looked a bit far in on first inspection.

 


Craig
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However.....all is not lost as I happen to have a spare cylinder sitting in a 4004 assembly I acquired some time ago....I'm confident it will fit.

 


Craig
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Identical.....


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