[alf]

back to testing:

RL1 and RL2 seem to be controlled by TR4 and TR5 if I am not mistaken.

the question I would ask do those two transistors have to be closely matched ?

in my case they are about 15% apart in their hfe values  ?!

i simply can not find anything wrong with the cam-wheels as i checked their fitting as per SM.

the cam responsible  for the lift & lowering just is not stopping as per correct sequence.

hard to believe no one has any ideas or pointers to help with that issue………too hard perhaps I wonder ?

ALF

[alf]

back from the workbench  after cleaning the 3 switches but no luck. The PU arm moves in, lowers but rises straight after again and so forth …l

i begin to wonder if the magnet inside the coil is moving as it should to move those two control arms for two

of the cam-wheels ?

one other question: does the hook of the metal rod which lifts and lowers the PU arm need to sit behind or in front of the white plastic rod the runs behind the PU arm assembly ?

your expert advice is badly needed 😁

thank you, ALF

[alf]

Sorry, I forgot to mention the table has had a complete recap – so, that should not be a problem source.

ALF

[alf]

Hi All,

finished the process of re-fitting all cam-wheels as per SM. Sadly the table still plays up.

looks like the next move would indeed be the removal of board 1 and give those switches a good clean ?!?

i do not feel overly confident this will be the problem fix as the table was working fine just before all this

started……but I shall try and will report back.

In the meantime please do not hold back with pointers …..

ALF

[alf]

Hi,

thank you for your reply, certainly always good to have clean contacts !

i am afraid but I decided to reset the cam-wheels as per service manual – I wished that manual is a tick more understandable using phrases like ‘….opposite h9le J’  when it actually means overlapping holes !! It can easily be misunderstood…never mind, I got it now.

in theory resetting those cam-wheels should fix the problem – I will report back.

ALF

[alf]

Hi Mark,

thanks to you too for your support and perfect pointer, much appreciated.

i can’t remember that I ever had a shorted cartridge…..suspension breakdown, cantilever broken, stylus dead yes, all of these but this one looks and tracks perfectly 😳

best regards, ALF

[alf]

Hi Martin,

good news, I swapped the fitted MMC4 for a MMC2 and bingo, the sound was back !!

to be honest, I never suspected the cartridge as stylus & cantilever look perfect and its suspension

is fine.

i wonder what happened internally ?

many thanks for  your guidance 👍

brst regards, ALF

 

[alf]

Hi Martin,

one thing I forgot to mention:

shouldn’t I be able to see a signal on its 7pin DIN connector pin 2 & 3

the resistance changes between those pins from about 900 ohm to 15 kohm

I connected the table to my Beomaster 7000, the data link works but still no audio signal

ALF

[alf]

So far I only did a complete capacitor check on the RIAA board and checked for any broken wires or suspicious soldering but not the two ICs yet.

ALF

[alf]

Hi Martin,

thanks for chiming in 👍

Yes, the needle is tracking perfectly and I can hear it when my ear is close.

I connected it to a Beomaster 8000, first into TP1 with its 7pin input, next into TP2 with its 5pin input, next into the RCA connectors with a 5pin adapter…..all silent.

i will try the Beomaster 650o next but unlesss the wiring to the BM8000 is not compatible I wouls expect the same result ?!?

ALF

[alf]

Thank you kindly for your reply….well, what can I say ?

I suspected amongst other possibilities a flatband connector issue and tried to open the flap-cover without taking the whole amplifier off the penta.

I could not totally open that cover housing pcb 2 but it might have had a strange impact to a degree that the penta now switches back to stand-by….figure that ?!!

i will keep in mind that very transsitor – thank you for that

ALF

[alf]

Thanks for all the replies, much appreciated 😁

the Penta surprisingly have recovered without explanation.

ALF

PS: i wonder if the “old forum” as I know has died ?!

[alf]

I am amazed, no one dares to comment constructively ☹️

not even BeolabPenta experts ??

Come on guys…..

ALF

[alf]

Perhaps to be more specific: i can turn the speaker off to Standby manually though !

ALF

[alf]

Hi,

yes, the BG4000 can seriously challenge you!

as far as the too early arm dropping you can readjust the assigned position spring if a wrongly adjusted spring is the cause ! That would only mean a screw driver and a few tries.

before you start doing this make sure all brass leaf spring switches are clean – if you have not done that ever unsolder the carriage motor connections (2 wires) after you removed the spring assembly plate (2 screws) with the attached red plastic indicator.

once that is done unscrew the position switch board, flip it over and carefully apply some very fine sandpaper like a 1500 grid or higher which you sprayed with contact cleaner. Hand-operate the switches and check they all make proper contact !!

put everything back together and check what happens.

if it still starts with 45rpm measure the Q4 signal which goes to 3IC4 – that flip-flop logic IC is looking after the 45rpm. That IC could be faulty or behaving erratic – not very likely but also not impossible though or simply is not get the correct voltage to prepare that IC for “work”

i just ordered a couple from the UK – they are not exactly cheap.

over time I found that many issues are indeed based on poor or no contact with those brass-leaf contact switches simply because they tend to oxidise.

my issue seem to have stabilised and the unsettling fact is I am not quite sure why ?

If I don’t “hammer” the ON key like it is a very hot surface meaning minimal very short contact but instead keep the ON key pressed for an extra fraction of a second the Beogram has not yet missed a beat…..figure that ?!

hope that gives you some pointers to check 🤞

ALF

[alf]

I fear that issue could be far more complicated as first assumed, documented by the erratic behaviour.

the brass-leaf switches are all cleaned and should have to play in the issue. The SI is stable at 6.2V.

suspects could be on the logic boards, however those flip-flop ICs are regarded as quite reliable?!

nothing can be more rewarding than a intermittent fault, finding its source even more rewarding.

the more important it would be to get some help……anyone ??

ALF

 

 

[alf]

A short update:

I have reflown the wire connection from Q4 mainboard and at the the connection next to 3IC4.

it had a positive impact but is still is not absolute stable ?
It also seem to have an impact on how long I keep the ON key pressed which is strange to say the least.

As the start up at 45rpm was joined by far to early tonearm lowering I will have a look at Q1 and Q0 as well.

the SI is present and jumps up to 6.2V but whether it is coming after a 10ms delay I am not sure – there is a delay when measuring the voltage but 10ms ??

anyhow, at the moment the BG behaves most times as it should but as said, not always.

you are still most welcome to chime in

Regards, ALf

 

[alf]

Hello,

yes, most certainly – items are located in Perth, western australia

shipping would not be a problem ?

thank you

ALF

[alf]

Hi Katie,

if the BG4000 is still available what kind of £££ are you expecting for it ?

you can PM me if you prefer.

Best Regards

ALF

[alf]

Yes, thanks Martin I am aware of this.

if anyone can supply please send PM with photo so I can identify if it is the correct board.

ALF

[Author]

Posts