Beogram 4500 (and others) main pcb question

[Jonathan McCall]

Idiot question I’m afraid.

How do I get this ribbon cable off ? The connector has a top clip which come off, however I’m not sure whether I should be giving it some welly to try and get it off after loosening the clip, or de-soldering the whole connector from the pcb.

Thanks

Jonny

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[Madskp]

I don’t know if it is the case here, but on some B&O systems the plastic parts i not a connector, but more a kind of strain relief for the cable. In that case you will have to unsolder. Not easy to see if that is the case here

Location: Denmark

[Jonathan McCall]

Thanks Mad – I’m thinking that’s the case here, as a firm pull doesn’t give any success. There is a YouTube video of Kose Trading just pulling the cable out on a Beogram 3000, but I’d prefer to take the educated route before getting ham fisted.

If anyone else can chip in that would be appreciated.

[Guy]

Clutching at straws but the service manual shows P6 as being a ‘socket 6-pins’ and in the exploded parts diagram PCB1 is shown with just the socket in place (no attached plug or wire showing).

The ‘plug’ would then be part of the connector from the muting module (module 11).

I think it should come apart.  (It’s possibly a old Molex right angle PCB connector – something like this:  https://www.molex.com/en-us/products/part-detail/09481064 )

IMPORTANT EDIT:  But the service manual does cover a variety of Beogram models so there may have been variations of connector – like in the BG3000 video that you mentioned.  Also, if you look at Condor Audio’s BG4500 restoration, the cable appears to be soldered directly to the board, perhaps another variation or a modification (possibly after breaking the previously connector – so be careful!!)  Condor Audio BG4500 pdf here (perhaps @yachadm of Condor Audio can comment):  https://www.condoraudio.com/wp-content/uploads/Projects/BeoGram-4500-Turntable-Restoration-Repair.pdf

EDIT 2:  This advert appears to show your BG4500 board with the connector disconnected:  https://kosetrading.com/product/beogram-4500-computer-control-circuit-part-pcb-1/

Location: Warwickshire, UK
My B&O Icons:

[Jonathan McCall]

Really helpful – thanks Guy. I’m using a component kit from Condor to recap the PSU board, main board and RIAA as well as new diodes, a couple of op-amps (SMD so will leave those to an expert) and new 33&45 trimmers.

I know it sounds like a know what I’m talking about, but I’m basically learning as I go along and it’s very interesting and fun following the circuit diagram and finding out what everything does.

Ive dropped Menahem an email on the connector, so hopefully he can help.

Cheers

Jonny

[Jonathan McCall]

The Kose board with just the connector shown was I think the same one from the video where the cable just pulled straight out.

Tried doing that again and no joy, so going with a de-solder. At least that will give me the opportunity to see how it all goes together.

The clip on top of the connector also appears to have little prongs to separate the cables as they enter the connector.

[Dillen]

It was not meant to be disconnected.
I always desolder the connector from the board.

Martin

[Jonathan McCall]

Putting everything back together, although still awaiting the RIAA back from my expert in SMDs.

Out of curiosity, can anyone enlighten me as to what the mica plate is for under the PSU board ? It appears to be a shield for the component that sits on top of it, to stop dust getting in, but allowing someone me form of cooling ?

I may be totally wrong, but always keen to learn.

Incidentally, that spring clip is a b ugger to get back on !

Cheers

Jonny

 

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[Jonathan McCall]

A very Happy New Year to everyone on the forum !

I’m taking the opportunity of a quiet couple of hrs to try and sort my 4500. Since getting everything back together I’m having a few issues. The arm won’t track, datalink doesn’t work and I’m only getting sound on one channel.

I think I may have found a culprit in the pesky ribbon cable I was talking about earlier in this thread. Two of the prongs (both outer ones) have become detached.

I’m not sure what they control, but it looks like I need a new ribbon cable.

Are these available anywhere ? I could get away with creating single wires in place of the broken prongs but would prefer the correct bit.

Thanks in advance.

Jonny

 

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[Jonathan McCall]

Couldn’t find a ribbon cable new or used so ended up making my own solution. Learned a lot about ribbon cables and connectors along the way.
My ribbon cable had a pitch of 2.54mm (1/10th inch) which was used back in 89 and is still in use.
This allowed me to find some Molex connectors which could be soldered to the board and I now have a bespoke cable set up with detachable connectors, which will make future fiddling a lot easier.

Hopefully I won’t need to do too much fiddling in future, as I’m pleased to say everything now works again as it should.

Tracking back on, both channels working and datalink operative.

Happy days !

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