Hi folks, I have a Beogram 8000 which exhibits "non-standard" cueing/lowering behavior.  Fortunately there's a simple work-around but I'd still like to investigate fixing it. 

When I press play, the tracking arm light comes on, it spins up OK and automatically cues the tone arm to the start of the record (works OK with any diameter, ie, 33 or 45).  However, it doesn't automatically lower the arm.  To get it to lower, I must momentarily press an arrow key (either one), then press play again.  When I do this it works perfectly every time.  And it's behaved like this for as long as I can remember (at least 20 years).  When an arrow key is pressed, it's only necessary to press it for a fraction of a second.  Not so long as to physically move the tone arm.  If play is pressed again but without pressing an arrow, the red light on the tracking arm begins blinking on and off.  Aside from this, it works normally.  So it's like the CPU is saying there's a problem with the cuing and it's not 100% sure it's cued up properly, requiring the user to "confirm" by moving the arm with arrows.  Perhaps this is a fail-safe mechanism to work around potential cuing problems (?).  Just a thought.  The fact that it indeed cues OK would imply that the sensor is working properly since it automatically cues any size record.  I couldnt' find anything in the service manuals which specifically address this issue.  I did make a few adjustments to the stop switch position to fine-tune the cueing.  Could it be that it's simply still not adjusted properly?  Ideas anyone?

 

Hi

 

I had a similar problem on my BG8002 which turned out to be related to the adjustment of the DC voltage on the photo sensors which form the basis of the << and >> manual movement systems.  I reasoned that if the voltages were set too high, it keeps the solenoid in the raise position and doesn’t allow the arm to lower.  The error in the adjustment is probably small and after you press the manual movement switch, it allows the system to respond to the PLAY signal.  The service manual states that the voltages on Pins 4 &6 on IC5,  has to be around 620mV and mine turned out to be closer to 900mv.  After adjusting this voltage with those two big black screws behind the control panel, everything worked OK. You could try that for a start.  Failing that, you might be up for the standard capacitor replacement program.

 

Regards

 

Geoff

Hi Geoff,

thanks very much for the input.  I really appreciate it.  I couldn't find IC5 on the partslists or on any of the PCBs.  Do you mean P5?  The manual says to adjust "Screw A and B" until 620mV is measured on pins 4 and 6 of P5.  I believe it's actually P5, not IC5.  Anyway, I adjusted those huge screws so as to get 620mV on the pins.  The voltage had been 738mV and 687mV.  It didn't solve the problem, unfortunately.  The work-around still works but I'd still like to fix it.  I have to say it's one of the more bizarre designs I've come across and terribly shortsighted of the engineers not to provide test points.

OK, does anyone have any ideas?  I'm totally stumped on this one.  For me, changing out all those caps would be a nightmare and definitely not worth the time.  Not sure why a bad cap would cause that behavior, in any case.  So the mystery remains: why must I press an arrow, then press play a second time to get it to lower the stylus??  Any ideas greatly appreciated!  Thanks for reading,

- Chris

 

Hi Chris

First of all, sorry for the incorrect reference - it should have read P5 not IC5.  I am afraid that my notes were wrong and they have now been corrected - well spotted.

Bad news that the adjustment of those screws hasn't fixed the problem.  I therefore conclude that the arm is arriving in the correct cueing position and stopping.  At that point, there should be a signal from the micro telling the arm to lower.  I would check that out next, P6.18 should go high if the micro is telling the solenoid to work and P3.1 should go to 5V or thereabouts.  If the voltages change then the micro isn't the problem.  If the voltages change and the arm doesn't lower then we would have a mechanical issue.  However, considering that when you press PLAY this sequence does work, I would expect to find that the micro was not sending the required "lower" signal.  In that case it must be getting confused for some reason and that could take you back to capacitor problems in the power supply.

On another occasion, I had some problems with this start up sequence and it turned out to be an excessive amount of ripple on the 5V power supply.  This was fixed by changing the large 2200uF capacitor, C24.  If you wanted to limit the amount of caps to change, I would check the characteristics of the 5V supply with a scope and change capacitors C24 and C20 to make sure that the micro was getting a good reset signal.

Keep looking and you always find the problem

Regards

Geoff

 

   

Hi,

Please, please don't start fussing about until you've checked all solder joints at connectors. My 6006 kept having random problems, including yours and it was completely sorted out after resoldering. Beware though, you can't see bad solders unless you use some magnifying glass to do your inspection. Look at P3 and P4 first. Hope that helps.

Jacques

At 41, my eyesight isnt'quite what it used to be when I soldered PLCC and SO chips for breakfast - so I don't bother trying to spot bad solders in old equipment anymore. I just redo them all. Then you will know for sure that they are good.