Beogram 4000 and also BG8002

[hcraig244]

Changed out the 47uf for the prescribed 0.47uf and its made a massive difference, not surprising as the 47uf is 100 times greater than it should be, reading up it acts as an integrator or filtering element. It smoothes out the signal coming from the tracking sensor before it triggers the operational amplifier to drive the carriage motor. Because the capacity is 100 times larger than specified, the circuit’s RC time constant  is elongated by a factor of 100. The tracking error signal must build up over a much longer duration (approx. 10 platter turns) before the voltage crosses the threshold required to activate the motor. All according to AI….every days a school day!

 

• This reply was modified 3 weeks, 5 days ago by hcraig244.

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[hcraig244]

As the deck I’m currently working on had undergone a re-cap we only sourced service kits for the other two, which now leaves us short of a 0.47uf  63v cap….I have in my stock a 0.47uf 100v cap that I will use for the next deck, I know that Martin frowns on such a selection suggesting that the capacitor gets “lazy” due to operating well below its capability….however 63v is also well above the operating voltage in this case so i think i can justify its use….comments always welcome ;¬)

[hcraig244]

The tone arm cover has lost a securing tab at some point in its life, the residue of superglue can still be seen on whats left of the tab…cleaned it up and re-attached it using Aleenes tacky glue, strong enough to hold it be easily removed when required

• This reply was modified 3 weeks, 4 days ago by hcraig244.

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[hcraig244]

The clip that holds the dust cover has also become detached, double sided tape…not the best solution in my view but it is what it is…..cleaned the residue away ready for epoxy

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[hcraig244]

Slid the hinge spindle in to ensure correct alignment prior to glueing…..epoxy is very unforgiving

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[hcraig244]

This cover has lost its stainless steel securing plate…cleaned the old double sided tape away and left it at that….also the fastening screw head has been abused in the past…oiled it a little to free it up as best I could….

 

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[hcraig244]

I’m now waiting for the epoxy to set fully before attempting to fit the dust cover, I also need to fix the side panel to the hinge with double sided tape, already done this to the aluminium trim on top, therefore its on test until I return from Liverpool Wednesday, me and her indoors are having a night out and a couple of drinks ;¬).

it’s nice to have what I think was the deck in the poorest condition behind me, famous last words I hear someone say!…..

• This reply was modified 3 weeks, 4 days ago by hcraig244.

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[hcraig244]

Little work on the dust cover required, the small rubber buffers sitting on the bottom of the cover have gone hard and mostly disappeared…drilled out the dead material and cut pieces from a old drive belt I use for this purpose, they need to be cut to size when the lid is in place.

 

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[hcraig244]

This done the dust cover fitted without incident, had to find a flat surface to ensure everything was lined up correctly, my workbench is very uneven, and one more test album says this is ready for collection.

This has been quite a learning curve helped largely by AI it has to be said, it helped a lot quickly identifying existing threads on the internet and providing links to said information…it did get it wrong occasionally and confused other B&O decks with the one in question so some discretion had to be employed…

Next up the deck which, on the face of it, only had a problem with the pick up arm not dropping which I traced to a poor connection to the solenoid coil…..we will see!

 

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[hcraig244]

Transport carriage first, this deck was already in the full service position due to me using it as a diagnostic tool for the previous piece….saved a bit of work, threaded rod was full of old grease along with the screwed collar, supporting rods where tacky from old grease too. Cleaned them up with ISP and a small brush, changed out the only two capacitors on the floating chassis at the same time. Discovered a broken tab under the front guide rod suggesting perhaps someone had been here in the past too……

 

 

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[hcraig244]

All reassembled and new drive belt fitted, used some oil I bought from a model train set shop that they use to lubricate the small gears in the engines to lubricate the screwed rod, gave it a test run. Always like to do this periodically to help trace any faults I may “build in” as I go along…..everything is still working fine.

 

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[hcraig244]

Main PCB up next……I know from Rudi’s posts that the capacitor lurking inside the IC canister would be a challenge so I went after it first….and I wasn’t disappointed, one leg un-soldered fine from the bottom of the canister but the other leg seemed to be soldered to a post internally?…I couldn’t get enough heat into it to loosen it off, I was concerned about this, in the finish I cut the leg off inside and with great difficulty managed to solder the new cap to the “post” internally….the other leg went in fine.

Given all the pulling and tugging involved I decided again to reassemble everything and give it a test…..everything still works correctly…..

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[hcraig244]

The IC canister behind me I moved onto the main PCB and as can be seen someone has been here before me, which is fine as I checked all the values of the replaced components carefully and all was well.

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[hcraig244]

Should have replaced these two while I had the canister removed, schoolboy error….however if you zoom in on the left hand side cap C4 (anyone following this thread will remember I had to replace the one fitted by another due to incorrect value) you will see it is actually marked 47uf….I can’t see a decimal in front and wonder if this had thrown the individual who installed it?….I checked it with a capacitance tester and apart from it being out of spec its clearly not 47uf and much closer to .47uf

 

• This reply was modified 2 weeks, 6 days ago by hcraig244.

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[hcraig244]

All caps replaced and ready for re-assembly, gave the terminal prongs a clean with a fibre glass pencil and flushed the plugs with DeOxit for good measure….the ribbon connector from the control panel feels quite loose….will have to watch that one.

 

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[hcraig244]

Fixed bracket isn’t fixed anymore so out comes the epoxy once again…..

 

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[hcraig244]

All done, sat on flat surface to trim the new rubber feet to the dust cover and put on test for an album….2 down I to go!

 

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[hcraig244]

This last one looked to be in the best shape of the three…everything seemed to work fine, full service position and noticed the detector arm was well low and needed adjustment to 19.5mm from the platter to the top of the arm sorted that then had to adjust the pickup arm to match, not an issue as i was going under there to take the drive screw out and clean it.

 

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[hcraig244]

This screw was filthy with old gummy grease and all manner of detritus sticking to it and the associated worm bush

 

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[hcraig244]

Connected everything back together and performed a test run to make sure I hadn’t introduced any faults….all good mechanically onto the capacitor replacement.

 

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