Hi all,

I need some help again.

I recently acquired a mint condition Beogram TX. The owner said it worked flawlessly and has been serviced some years ago. And yes, it works flawlessly. Except for the automatic speed control (obviously the average user doesn't care about that).

Which means, if I play a Single, the Beogram will sense the record and drop the arm at the right place. But speed stays at 33rpm and I have to select 45rpm manually.

As I'm a bit annoyed by that I took a look inside the Beogram, hoping it was just a bad solder joint or something like that. Sadly it wasn't. But at least some other surprise - there's a Datalink module in there. Looks like 'service' meant someone replaced the PCB with one from a 6002...

So before I completely disassemble the Beogram to search for a faulty component: Is this a common fault? Any suggestions on what could be wrong?

The TX doesn't count pulses like the BG8000 etc. but instead has a sensor and a ruler, more like the BG4002.
I seem to remember there's a metal ruler inside with holes for the lowering points.
Maybe some dust have settled there or in the sensor(s) ? Or a sensor is at fault.

Martin

Yes, the TX uses a metal ruler. But everything is fine there...the sensor and the LED work fine. And as the BG stops and plays the record the problem can't be there, can it?

As all connections are ok the problem has to be somewhere on the main PCB; most likely around TR35.

So I checked all parts mentioned in the service flowchart (D45-46-47-48-49-50; TR35-40, C40-41). All were still good, but I replaced the two caps and the two transistors anyway (why not - I still had new parts).

And now the problem got even stranger. At the first try it didn't work - just like before. But since the second one speed is stuck at 45rpm! Which means when I start the BG it will start up in 45rpm mode and will play LPs in the same. I can still change the speed manually - so it's more or less the same problem, only the speeds changed!

Does this mean IC3 is faulty? I don't have an oscilloscope to check...

Edit: Ok, forget that part. 33rpm doesn't work at all now. Turntable stays in 45rpm mode no matter what you do....

Well, if there's now a new fault, I suppose it will have to
be something that you introduced so check what you've done before diagnosing any further.
Reverse it if need be.
Check especially the PCB tracks. Some of these boards have a nasty tendency to
develop cracks where the tracks meet with the solder pads and you can
only see them using a microscope or measure with a meter. The heat from soldering
seems to increase the risk, especially if soldered using a too high heat setting.

Check also for clean power supply voltage with no ripple.

IC3 is a cheap component, it's also a CMOS chip so it's sensitive to static electricity
which again means that any work and handling of the board will have to be done
in an ESD-safe environment. Even the tiniest amount of static can introduce scars within
the chip that sooner or later develop into real faults.
I suggest you replace IC3, just in case.
And then measure its function, it's more or less a standard flip/flop circuit, set and reset
by the 33 and 45 switches, so shouldn't be too hard to diagnose, even with only a multimeter.

Martin

Hi again,

Dillen:

Check especially the PCB tracks. Some of these boards have a nasty tendency to

develop cracks where the tracks meet with the solder pads and you can
only see them using a microscope or measure with a meter. The heat from soldering
seems to increase the risk, especially if soldered using a too high heat setting.

Many, many thanks for this hint. This indeed was the fault that caused the new problem as well as the old one. I didn't use a really high heat setting and yet that was enough.

But I think the problem is rather the solder itself - measuring with a meter from solder pad to solder pad showed no problem. After removing the old solder and replacing it with new one everything works fine again - even the automatic speed setting.

It took this long to find out as I replaced a bunch of components first (the seller was kind enough to send me a spare PCB) only to find the problems unaltered...