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ARCHIVED FORUM -- March 2012 to February 2022
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This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022

 

A Beogram 4000

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Craig
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Replacement reed relay turned up over the weekend.....looks a lot smaller then the original but is functionally the same..

Craig
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Went in easily and works a treat.....scale illumination now comes alive only after the ON switch is activated.....

Craig
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This problem sorted I have moved on.....Now everything is good up to the record detection circuit, with or without a record on the platter the tone arm moves to the 25/30 position and stops followed by the lower command.....looks like the photo cell, or its circuit, is sensing a record in place at all times....not seeing the platter ridges and providing the required pulse perhaps, or just not working at all, this is what I get at the output of the photo cell into 1C9....poor pic I know, camera not fast enough I suspect.

Craig
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Following on from a bit of rational thinking, not something I'm known for, I disconnected the photocell from PCB1 and hooked it up to the scope. powered ON and stopped the detector arm mid way and spun the platter by hand

Craig
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Got this pulse through all the noise the scope was picking up....looks good enough to me, and it is in sync with the speed at which I spin the platter....so I need to look downstream I think.

Dillen
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Dillen replied on Wed, Dec 12 2018 8:43 PM

Also - check the lamps position in relation to the lens system.
It needs to sit right in the sweet spot.

Martin

Craig
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Cheers Martin....I'll have a play with the position, carefully ;¬)

Meanwhile I took this shot of the scope measuring at the collector of 1TR14 and I don't think it looks a million miles away from where it needs to be...

Craig
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And this is what I'm getting at the collector of 1TR15, again it looks sort of as it should......

Craig
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Craig replied on Wed, Dec 12 2018 9:53 PM

But I'm loosing it at the base of 1TR17 no pulse whatsoever...replaced 1C14, which had leaked, to no avail......time has overtaken my efforts this evening, back for another go tomorrow Indifferent

Craig
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Spotted something this evening by chance.....was measuring the DL signal into the logic to tell it that there's a record in place HIGH pick up arm can be lowered, LO pickup arm is blocked. The measurement was HIGH at 5.9 vdc

Craig
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This is the signal I have been getting all the time with or without a record on the platter.....however I switched on my magnifier lamp and the signal dropped to LO.....I have repeated this several times and switching my lamp on/off switches the signal from LO to HIGH....

Craig
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Craig replied on Thu, Dec 13 2018 8:38 PM

I'm thinking that the detector arm circuit s working fine....and that its possibly the photocell no longer sensitive enough, I have tried adjusting the lamp position and also removed the arm so as to hold it varying distances from the rotating platter.....no response at the DL output, I have a OSRAM FSH component I will try to fit...….is there any way of measuring the photocell to determine its condition....it could still be a transistor gain lo in the detector circuit?

Craig

Craig
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The OSRAM arrived yesterday.....however I disconnected the photocell and measured the signal level when not tied to anything else and god a pretty good signal....this is with the scope set at 10mv div.....I'm reluctant to mess with this 

Craig
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With great trepidation I have embarked on the replacement photocell journey...unsoldered the lamp holder and removed it, as was reported the OSRAM unit is much larger than the space which it will occupy....

Craig
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The Dremel was instrumental in removing most of the excess material and I finished off with fine emery paper until I god a snug fit...

Craig
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Re soldered the connections and assembled the lamp holder complete with its new photocell and powered up....this was the reading on my scope at the Base of TR14....looked very low at around 10mv

Craig
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I should have said at this point the platter is spinning at 33rpm and I have it held over the ribs......this is the trace at the collector of TR14, nicely pumped up at around 1v....

Craig
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And at the collector of TR15 a decent signal too...

Craig
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Base of TR17...….

Craig
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And finally the emitter of TR18......

Craig
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The output DR to the control logic is also now sitting at around 0vdc and so sending the lower arm blocked signal, however the arm is roundly ignoring this command for the time being......not to be put off I'm happy to have the detector arm and its associated circuit finally responding as design...….

Craig
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Bit of an investigation into a floppy cartridge connection has led to an email being fired off to Rudi...……….

Craig
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While awaiting Rudi's shapeware parts to arrive, and also for the Christmas pudding to digest, I have taken a closer look at the cartridge mount bits that I will need to retain and connect to Rudi's modified connection strip, the screen/ground spring connector looks pretty shot.....I will need to be a bit creative with this I'm thinking....

Hugo
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Hugo replied on Wed, Dec 26 2018 11:51 PM

Hi,

 

congratulations with that work on Beogram 4000 (I fortunately own one).

About the aluminium Trim Strips, how can i found the member that had some replic´s?
Best regards

musicismoving
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Hi. I am the member who has the aluminium strip. Let me know your requirements. 

Barrie

Craig
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Craig replied on Sun, Dec 30 2018 1:02 PM

seems I have broken a couple of the very thin wires which connect to the cartridge holder when I removed it, can anyone advise what AWG size these wires are (Martin.) I,m still awaiting Rudis package 😉

sonavor
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sonavor replied on Sun, Dec 30 2018 9:58 PM

For inside the Beogram 400x tonearm, from the cartridge connector to the rear board (that transfers to the really thin magnet wire) I like to use 32 gauge wire like this.  It is nice having the color coded wire as the Beogram 8000, at least the one I opened up, has the really thin, non-color coded wire all the way to the cartridge connector. 

-sonavor

Craig
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Craig replied on Mon, Dec 31 2018 12:01 PM

Cheers Sonavor…..found this on UK ebay ;¬)

 

https://www.ebay.co.uk/itm/Internal-Tone-Arm-Rewire-cable-by-The-Missing-Link/232591653167?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

Craig
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Rudi's package arrived so as I'm still waiting for the tonearm wire I decided to install the replacement LED into the detector arm....

Craig
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And for good measure stripped down the release lever and associated solenoid and damper...good clean and some silicone grease.

Craig
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This lever was quite stiff and took a little easing off....

 

Craig
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Re assembled and ready to go....I have to say the whole thing now seems very tight, not  loose....I'm wondering if the silicone grease may have been a bit to viscous,

Craig
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Craig replied on Thu, Jan 3 2019 8:32 PM

Alister of Audio Originals kindly offered to take a look at my cartridge in exchange for the loan of my magnet alignment tool, he has a bunch of drivers with slipped magnets, therefore without a cartridge I cant confirm if the arm is dropping and lifting exactly as it should but the solenoid is pulling in and the release lever is moving up out of the way therefore allowing the arm the possibility of dropping....so in all it looks promising, the detector arm is now working well too.....seeing the plater ribs with no album present and allowing a stop and drop when one is.....so I'm encouraged so far.

Craig
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Tone arm wire turned up today so had a crack at soldering the wires to Rudi's shapeways connection arm...….these wires are very fine, more like soldering hairs!

Craig
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Fixed the bottom half to the new topworks…...

Craig
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soldering the tonearm wires, bottom ones are a challenge...….

Craig
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Mr Roast dropped his BG4000 off over the holidays for me to have a look at, seemingly it was refusing to detect the presence of an album on the platter and behaved accordingly....run to the centre of the platter and returned, on examination I could find nothing wrong with it....worked everytime on both 33 and 45 discs......very odd. However as I was sure dave wouldn't mind I "borrowed" his cartridge in the interests of science...……...and plugged it in

Craig
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Craig replied on Sat, Jan 5 2019 3:40 PM

I'm delighted to say that mine also now responds in a similar manner, connected up to Peters Beolab 5000 and had a listen, all is working just as it should on both 33 and 45 discs......sounds pretty good too for an old girl ;¬)

Still got a bit to do of course, now the thing is actually operating within pre defined parameters I will go ahead and fit Rudis remaining LED conversions, full recap and look to music is moving for a new trim, also need some albums to listen too......been a bit of a slog but light is at the end of the tunnel

MrRoast
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MrRoast replied on Sat, Jan 5 2019 6:37 PM
Glad I come in useful occasionally Big Smile. Odd about the 4000 - must just be me! [:\'(]
sonavor
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sonavor replied on Sat, Jan 5 2019 7:09 PM

Measure the voltages of the fixed arm sensor with and without a platter present. It sounds like the voltage level could be marginal. 

-sonavor

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