The Workbench

Re: Beomaster 8000 tuner : nothing past 97 MHz

chartz — Tue, 20 Dec 2011 10:39:42 GMT

Hi,

Finally found the remote... but still no processor module!

Re: Beomaster 8000 tuner : nothing past 97 MHz

chartz — Sun, 30 Oct 2011 15:46:23 GMT

Hi Olly,

Well the last one went for 380€!

It wasn't even looking good...

Olly, I still have that Beocord 9000 pinch roller for you!

Re: Beomaster 8000 tuner : nothing past 97 MHz

Step1 — Sun, 30 Oct 2011 15:39:48 GMT

How much are they going for Jacques? I figured they must fetch a fair sum but as I have not yet seen one sell on UK ebay I haven't a clue what they are worth!

Re: Beomaster 8000 tuner : nothing past 97 MHz

chartz — Sun, 30 Oct 2011 10:58:26 GMT

Hi all,

This is pathetic. Still no idea what to do. Ever since the 7805 change the tuner has remained stable, but it won't go over 102 MHz.

I haven't been able to source another processor board. The last Beomaster 8000 receivers I saw on eBay were sold for ridiculous prices and they weren't even nice to look at!

Re: Beomaster 8000 tuner : nothing past 97 MHz

chartz — Wed, 28 Sep 2011 12:28:40 GMT

Yes, they are in place!

Re: Beomaster 8000 tuner : nothing past 97 MHz

hemenex — Wed, 28 Sep 2011 12:24:44 GMT

Did you already try the 100nF blocking ceramic caps directly at the processor's supply as me & Olly suggested?

Re: Beomaster 8000 tuner : nothing past 97 MHz

chartz — Wed, 28 Sep 2011 12:08:31 GMT

Step1:

Put a hinge on the thing

Opened the can again. Nothing wrong in there... Xtal just fine.

Checked the protection zener (D6), the cap (new). I get 4.93V, 4.97V with processor unplugged.

I'm going to give up, unless someone comes up with:

1) a stroke of genius,

2) a processor board for rent!

Re: Beomaster 8000 tuner : nothing past 97 MHz

Step1 — Mon, 26 Sep 2011 11:13:53 GMT

Put a hinge on the thing

Re: Beomaster 8000 tuner : nothing past 97 MHz

chartz — Mon, 26 Sep 2011 11:05:25 GMT

Opening that can again... not something I'm looking forward doing!

Re: Beomaster 8000 tuner : nothing past 97 MHz

Step1 — Mon, 26 Sep 2011 03:52:25 GMT

I guess it is a bit of a stab in the dark Jacques but unless anyone else thinks otherwise you not got a lot to loose? Of course, you still can't entirely rule out the processor but it is looking much less likely now!

Re: Beomaster 8000 tuner : nothing past 97 MHz

chartz — Sun, 25 Sep 2011 16:09:32 GMT

Hi Olly,

The inductors are fine. Do you mean the crystal itself could be the cause of the problem?

The frequency counter increments fine (displays correctly) but I'm not a processor specialist... Some kind of instability happens somewhere but I can't see it. I wish I knew how to test a processor!

Thanks for suggesting this. A new 2MHz Xtal, perhaps?

Re: Beomaster 8000 tuner : nothing past 97 MHz

Step1 — Sun, 25 Sep 2011 15:28:39 GMT

How strange, and frustrating Jacques, I feel for you mate! Definately sounds like a noise issue! How do the little supply inductors look? They aren't unwound / distorted or otherwise in-effective are they? Have you looked at the crystal area I am sure it isn't impossible to have a minor stability issue that throws off certain functions...? How about a small decoupling cap actually across the micro supply pins and lay the thing across the chip body? I dunno, funny ideas for a funny problem!

Re: Beomaster 8000 tuner : nothing past 97 MHz

hemenex — Sun, 25 Sep 2011 13:49:34 GMT

I always put a ceramic 100nF between + and GND on my controller's power supply.

There seems to be a 1nF only here; can't see if they are ceramic - sadly I don't own a BM8000: I would put those 100nF in parallel to C16 / C46 and try again as filtering the 7805 obviously helped a little.

Just a thought....

Gunther

Re: Beomaster 8000 tuner : nothing past 97 MHz

chartz — Sun, 25 Sep 2011 13:33:04 GMT

No difference, I tried mylar and ceramic. Still stuck at 102.

Re: Beomaster 8000 tuner : nothing past 97 MHz

chartz — Sun, 25 Sep 2011 13:13:15 GMT

tournedos:

chartz:
Yes I did fit a 22µF cap across the new 7805 (out), and a ceramic 100nF (in).

According to general knowledge on the 78xx regulators (with no specific experience on the BM8000, and I'm not going to argue with Martin if he tells you otherwise for this application), these regulators are prone to oscillation if you have (only) an electrolytic directly on the output. I would replace it with a 100n ceramic, or at least add one there as well.

I know. I've used them for 30 years and I always put a 100nF mylar at the output as safe practice. Why did B&O didn't do it in the BM8000 I wonder. They did put a 330nF before though. Let's see what it does!