Hi all,

I am currently restoring a Beogram 8000. I changed the caps, resoldered joints, replaced a defictive IC.

Luckily this unit has a metal tacho disc. However I am quite sure the light sensor has gone. (Call it short circuit or overload of the led or just mechanically, it simply doesn't give any sign of life)

I have read in one of the threads that the light sensor of the tone arm has been repaired with some units of an old computer mouse. Can I use similar components for this sensor or does it need a special kind of light sensor. (What will be the type?)

Thanks in advance!

 

An easy way to tell if the IR LED is emitting light is to use a digital camera (most cell phone cameras will also be fine), the IR light from the emitting LED will show as a pale blue spot.

IR receivers are generally more realiable than IR emitters but of course they can fail. A voltmeter or oscilloscope on the signal lead and something to interrupt the light will tell you if the receiver works.

It's correct that parts from some older types of computer mouse (the types with the ball underneath) will work but I don't think this particular opto part will be hard to find. The opto at the end of the threaded shaft is different in that it has two receivers, giving a 4-phased output to allow the electronics to count either up or down. The tachosensor merely sees light or dark.

Martin

Thanks for the quick reply Martin,

The previous owner disintegrated the opto assembly. The receiver will transmit some sort of a signal. The IR emitter seems broken. As the complete assy is!

The spare parts I have consist only of seperate receiver and emitters. I was wondering if there are any standard assys available. If so, what are the partnrs. to look for. I tried to check Conrad and Farnell. No success so far.  

btw. is it you Martin that has spare drive belts for Beocords available? I am in need of the drivebelts for the Beocord 8000. Just received a complete (non working) 8000 set. Receiver is already up and running.

Yes, that's me.

There's a good chance that I have a good used opto part in stock but I have a lot of things temporarily stored in boxes due to water damage in my repairshop so I have very limited access to parts at present.

Maybe some other Beoworld'er has one from a scrapped deck ?

PM me for the belts.

Martin

I think I just found some on Farnell. Suppose the voltage for the IR-transmitter is 5V and the receiver will work like a transistor and is able to switch approx. 15V to 0V when active.