ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Hi there
I want to let you know how i got my new Beogram 8000 back to life.
As it came to me the deck looks very good in optical condition, the aluminium platters from the tonearm cover and the big platter became lose so far nothing difficult.
The main problem was that the platter didn't spin at all, just a short backspin when the tonearm came to it's restposition. So the brake circurit is working.
The tonearm moved inwards to it's desired position and travelled inwards when i touch it slidely to the left direction, everything OK so far.
After recapping all the caps and resoldererd everything on the mainbord incl. the processor board the platter won't spin at all.
I was a bit confused about this and startetd to measure the rail voltages.
+ 15 was Ok
- 15 was only about 12 Volts.
Input from the rectifier was about -22 Volt.
I changed the Transistor TR19 and the Z Diode D26. This resulted in nothing, same -12 Volt again.
I picked up my Oszi and looked at the 12 Volts, there was a humming about 3 Volt PP in no specific frequency.
Scratced my head tree or four times measured here and ther , no miracle to find, values of the Resistors and transistors seemed to be OK. In my despair I soldered a 100nF Capacitator, which was lying on my workbench, to the legs base and collector of TR19.
The humming was gone and the rail Voltage is steady about 15 Volts.
But the platter didn't spin
My investigation brougth me to IC 3 and it's In and Outputs.There was a small signal on pin2 but nothing on pin3, so i desoldered transistor TR 26 nothing changed. I measured Output pin7 of IC3 an there was 13 Volt nailed. Nothing changed at the output no matter wich speedknob i triggered.
I took a look at the inputs. Pin 5 steady about 3,5 volts as desired and changing voltages at pin 6 wich get's different voltages from the uP.
The 13 volts at the output of IC3 Pin 7 activates TR26 and pulls the signal from input IC3 Pin 2 to ground.
I swapped the IC 3 and et voila the platter starts to spin again at the correct speed
If you ever have trouble with IC 3 figure out if you use a IC socket or not because the construction with the 2 subplatines has to be new aligned about the height of the IC socked.
After all i mounted the new tachodisk from Martin wich came fast delivered with a perfect packing and an perfect desciption how to change the disk, thank you once more Martin.
Now i've to do some final cosmetics and i'm proud to qwn such a delicate record player.
I hope you did understand my broken english so far and my post is in the right forum
Best regards and keep the beograms alive.
Christian