Beomaster 6000 (2702) restoration: mounting the FM dial display and fixing a new dial cord

The FM dial display has been restored before (click here). One thing I forgot to mention is the importance to have the dial band under the tiny clips that guide the band in a straight line and avoid it rubbing against the red plexi panel that comes on top. These clips are so tiny that it's easy to not spot them.

On most units that I have restored the dial cord is broken (or about to be). The cords used on a Beomaster 6000 quad are very thin (about 0,4 -0,5 mm diameter)  compared to cords on many other vintage radio's. That's probably why it is extremely difficult to find vintage cord with that size. The best alternative that I have found is fishing line. I know that some hardcore vintage restorers will hate this, but it works, if you select the correct type ! The typical yellow/transparent nylon ones will NOT work. They are to stiff and slippery. I have good experience with high quality DAIWA 8EVO Tournament Braid type of 0,45mm.

There's a drawing in the service manual that describes exactly how to fit the dial cord. Important is the 3 turns on the main pulley, the 2 turns counterclockwise on the shaft coming in from the top and leaving at the bottom.

But before you break your head on this drawing and try to figure out the correct sequence of fitting the cord, watch this excellent videoclip by Beolover that shows you exactly how to do it in this post: click here.

Below is the DAIWA fishing line cord installed on this unit.

The dial cord is attached to the FM dial band with a plastic clip with 3 dents. Best is to remove some tension from the cord before attempting to fix it on the clip. A small dot of glue will help it stay in position once you have the correct setting. Tuning into a known FM frequency and then set the red line to the corresponding numbers on the red plexi display is the way to do it. It often requires a bit of trial & error to get it correct.

The next posts will mainly be on the restoration of the key panel, the red plexi display and the wood plinths. We want this Beomaster 6000 quad to look as good again as it sounds ! And that will require some different skill sets other than electronics.....

Beomaster 8000: No Tuning Above 93 MHz

A 'Beofriend' sent me an email about an interesting tuner issue, which is closely related to a problem I had last year with a Beomaster 8000. In my case, the tuner would not respond to the frequency setting with the rotary encoder, and when set to a frequency close to 91.7 MHz, I could hear the stations of the entire frequency band 'zoom by', either up or down, depending on being slightly below or above of 91.7 MHz. The relevant blog entries are these:

http://beolover.blogspot.com/2013/09/beomaster-frequency-counter-feedback.html

http://beolover.blogspot.com/2013/10/beomaster-8000-tuner-repair-exchange-of.html

Now, the problem described by Beofriend was that the Beomaster would properly respond to the frequency setting in the lower range (he said below about 93 MHz), while in the upper range the 'zooming' issue would occur. Very interesting!
It turned out that the cause for this was a broken flip flop chip, which is in the frequency feedback after the prescaler for a further frequency division by 4 to make the signal palatable for the ancient 6501 micro controller IC4 (which runs on a 1 MHz clock, i.e. anything above this frequency appears as a blurred whirl to it...hard to believe that there was a time when 1 MHz was considered 'fast'...;-).
Here is the relevant circuit diagram section:

After replacing IC8 everything worked again.
I really wonder how these ICs can fail (in my case the prescaler (IC5) needed replacement...In my opinion the most likely failure method for silicon is a too high operating voltage or too high signals. Probably another reminder to put our cherished Beomasters on uninterruptible power supplies (UPS) to put a buffer between them and the power grid/lightning strikes...