Beogram 4000 start issues again

[alf]

Hi Everyone,

the Beogram is behaving strangely:

with ON activated the carriage moves in but the arm drops way to early and the platter spins at 45rpm ??

If corrected “manually” I can play any record, no problem.

following the fault-finding chart in the SM I end up at “replacing 3IC4” which is the FCH131 flip-flop IC.

i changed over twice but obviously that showed no impact on the fault, concluding either both spare ICs are bad or the fault has a different source !

After cleaning all position switches still no improvement……?!
Looks like I have to revisit the training documents for better inderstanding, however that issue shows most times at the moment but not always when testing and that is really irritating.

would be the grateful for some pointers / advice

thanks guys

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]

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

 

 

[etype76]

Hi Alf,

Funny you should mention this issue as I’m currently having the exact same problem with my BG4000. Although I’d say it works perfectly 90% of the time but every now and then when I press ON it automatically switches to 45rpm. This is sometimes accompanied with the arm lowering early before the record although that seems to be even rarer. They sometimes occur together or independently. Both can be corrected with the buttons. Unlike you, I virtually have no electronics skills save for simple soldering so will not touch. If it mechanical then I could have a go. Could it not be the position of the springs?

 

[etype76]

I’m wondering too if the very warm weather (where I am) has altered some tiny margin and is causing it.

[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

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