Just had another look at the SM circuit diagram 1:

would it be a good start checking that OP amp 2IC6 ??

that one is handing over the FM signal  via P10/pin1 and 4 to the preamp - board #3 P19

ALF

Hi ALF,

Is the distortion in one channel or both?

2IC6 is a good place to start. What are the DC voltages on the chip?

I had a TL072 fail on the filter board 4IC2 on a BM8000 for no apparent reason, it was distorting badly. It failed after I'd changed all the caps, I replaced it with no other changes and it was all good.

Regards

Lonnie

Hi Lonnie,

the distortion was in both channels....all fine after I swapped boards.

in the meantime I replaced 2IC6 but won’t be able to test until all other boards are done.

let’s hope it did the trick ?!!

only the processor board to do (i hope) and thinking about changing the two crystals as well while I am at it ??

they should both be short-wired before being put in, right ?

will keep all posted

ALF

Hi Alf,

I wouldn't change the microcomputer crystal oscillators unless you know they are faulty or doing a restoration where the owner lives far away and shipping costs are outrageous.

The microcomputer board is easy enough to get to and can be done later if necessary. Why risk it when you don't have to?

If you end up having to I believe I sent you links before to the details Rudy and I have posted on the Beolover Blog.  You can't just change only the crystal oscillators either. Each oscillator has two capacitors that control the oscillator frequency.

John (sonavor)

Hi John,

as always, good to hear from you 😁 thank you for your advice - point taken !

going through Rudys blogs though it just struck me as ‘one of the things to do’ when a BM8000 restoration is under way?!

down here it is not as easy to get access to those parts, so I grab it while I can - yes, the two crystals with two pairs of 18nF caps 🤙😁

will store them just in case.

the processor board needs attention:

the memory chip seems to no longer does its job as FM stations won’t get stored,

the 22uF cap needs replacing and I was going to

provide the two big processors decent tulip-style sockets........

that is it for now - looking forward to read further comments, ideas etc.

ALF

As I said, if the BM8000 is being restored for an owner that lives somewhere far from us, where shipping cost is a factor (i.e. USA to Australia), then we change out the oscillator devices as extra insurance. 

John

Bad news I am afraid:

fuses blowing on the #7 board and I fear the standby transformer has a short ?!

if 3OT1 is disconnected from #7 board fuses stay on, if reconnected fuses blow !

it is not the power supply board as after disconnecting P52 fuses still blowing 🤬😢

looks like I have to chase the almost impossible replacement for that standby transformer 😢

unless one fellow Beoworld member can help ?

ALF

That smaller transformer is for the 5 VDC and +-15VDC.

I am not presently in a location I can check anything so I'm just going from memory. There are other things besides the small transformer that could cause your problem.  You could always pull the small transformer and check it out by itself.

Hi John,

yes, understood , it is for those 3 voltages.

the transformer is disconnected from the PS board #6 !!

the moment the HV side of the transformer is connected to board #7 the fuse blows 

if the HV side is dis-connected the fuses stay on. The HV is getting about 238VAC, coming straight from the AC mains.

I believe board #7 is doing its job.

perhaps there are other sources causing that problem - sadly I do not have the equipment to do any further testing of that stand-by transformer.

are you be any chance implicating the main transformer ?

ALF