The Workbench

Re: beogram 6006 platter not moving, coils are humming

jens m — Sat, 25 Apr 2009 02:34:37 GMT

hi martin!

no, it´s the right transformer, and as said after i replaced the caps, it worked perfectly for nearly two years, problems just came up last week.

i think i will put the beogram off the desk for some days and give it another try then...

thanks a lot martin for help and patience!

have a nice weekend!

jens

Re: beogram 6006 platter not moving, coils are humming

Dillen — Sat, 25 Apr 2009 02:06:56 GMT

You are not using a 60Hz transformer module in a 50Hz area or vice versa ?
Beogram 6006 / 8000 / 8002 won't work with stepup/stepdown voltage converters if the mains frequency
is wrong compared to what is printed on the transformer module. The transformer module needs to match the local
mains frequency.

I wish I could guide you further, but I think this is one of the cases where a trained
technician needs to take a look at it.

Martin

Re: beogram 6006 platter not moving, coils are humming

jens m — Fri, 24 Apr 2009 16:15:35 GMT

hi martin!

i measured voltage acros the sensor and it seems to work. when blocked, it reads out ca 15volts, otherwise it´s around 3 volts.

the humming is rather constant and not once per revolution and starts as soon as the gram is plugged to mains, but becomes louder, when play is pressed and the platter tries to go to 33.33 rpm.

jens

Re: beogram 6006 platter not moving, coils are humming

Dillen — Fri, 24 Apr 2009 15:37:25 GMT

A scope would provide the best view of the pulses but you can try to rearrange
the sensor slightly inwards or outwards and see if it changes anything.

The humming once per revolution is a typical symptom of a bad
tachodisc (not in this case unless some holes are blocked or the disc is dented) or misadjusted opto sensor.

Alternatively, measure the voltage across the sensor when over a hole and while not (rotating the spindle
very little by hand).

The eddy-current coils are quite power guzzling ones and if not run correctly, they will easily
draw enough current to blow the fuse.

Martin

Re: beogram 6006 platter not moving, coils are humming

jens m — Fri, 24 Apr 2009 15:23:05 GMT

hi martin the tachodisc is a new one, steel, i´ve got it from you.

my new observation is, that when the gram is plugged to the mains, it turns backwards for a second, then becomes slower and turns then the right way round...

still the coils are humming and the transistors at next to the coils become quite warm.

how can i see, if the signals from the opto are ok? is this possible without a scope?

thanks for your help + patience!

jens

Re: beogram 6006 platter not moving, coils are humming

Dillen — Fri, 24 Apr 2009 14:54:29 GMT

Please don't replace components in panic, you may introduce new faults.

Is the tachodisc OK ? Is it a steel disc or a photographic ?
Are the sensor pulses from the tachodisc opto OK ?

Martin

Re: beogram 6006 platter not moving, coils are humming

jens m — Fri, 24 Apr 2009 04:53:33 GMT

i double checked and resoldered all connectors and measured through the ribbon cable between processor and mainboard. everything seems ok here.

then i started renewing transistors and the op-amp in the drive circuit, by the state i´ve reached till now nothing changed in the behavior of the gram:

it starts spinning slowly as soon as it is pluged in and with a vinyl on the platter i realised, the speed is not 100% stable, but something like an oscillating fault like every two seconds.

i think i wil go on with the transistors in the drive circuit... just can`t find a replacement for the J175...

0tr2, 0tr3 (the ones on the bottom of the gram) and the bd438 on the small pcb still become rather warm when running.

i´m a bit puzzled, if the fault comes from the cpu giving wrong signals or if it is through the drive circuit?????

jens

Re: beogram 6006 platter not moving, coils are humming

jens m — Thu, 23 Apr 2009 17:35:13 GMT

hi martin,

sorry, i mistook c27 on the mainboard and c27 on processor board and was mixing up all a bit

yes, i exchanged the 2200μF and connected minus towards c20 minus to close the gap due to the missing connection with the new cap.

i will check solder joints and the ribbon cable tomorrow.

thanks a lot for your help!

jens

Re: beogram 6006 platter not moving, coils are humming

Dillen — Thu, 23 Apr 2009 12:58:27 GMT

The C27 I am referring to is the largest capacitor on the main board, a huge
aluminum can, 2200uF if my memory serves me right.
It will have to be replaced along with almost all other electrolytic capacitors in the Beogram.
When you replace it, you will notice it has three ground pins of which two are used and must be connected
together again when you mount the new cap, unless you can find a cap of the exact same
type (which is practically impossible).

Martin

Re: beogram 6006 platter not moving, coils are humming

jens m — Thu, 23 Apr 2009 12:48:58 GMT

hi martin!

i haven´t had your cap kit, only your tachodisc and took caps from the shop around my corner.

i replaced the 47μF cap inside the metal shielding of the cpu, according to the service manual it´s C28; minus is connected to ground/to the metal case, but i think my connection is pretty much the way it was before, so if you refer to a chnge in how the cap should be connected, i probably havent done it.... i didn´t touch C27 4,7nF though.

i already resoldered the connectors, but i will check one more time to make sure, and will check the ribbon cable coming from the cpu.

thanks alot for your help!

jens

Re: beogram 6006 platter not moving, coils are humming

Dillen — Thu, 23 Apr 2009 11:55:07 GMT

Seems to be a floating control signal.
Resolder all plugs and connectors.
Also the row of solders where the ribbon cable from the processor goes to the main board and check that no
leads in this cable has broken.

When you replaced C27, did you remember to introduce the ground connection
as shown in the cap kit inlay sheet ?

Martin

Re: beogram 6006 platter not moving, coils are humming

jens m — Thu, 23 Apr 2009 11:09:16 GMT

Re: beogram 6006 platter not moving, coils are humming

jens m — Wed, 22 Apr 2009 15:15:50 GMT

beam me up, scotty!

Re: beogram 6006 platter not moving, coils are humming

rayfenwick — Wed, 22 Apr 2009 14:59:48 GMT

I hadn't thought about it, but yes the platter must be on or they go a bit mad. My non B&O induction turntable used to go into warp speed...

Re: beogram 6006 platter not moving, coils are humming

jens m — Wed, 22 Apr 2009 14:45:24 GMT

hi martin!

i´ll try with the upper platter tomorrow, perhaps i´m lucky and it will run smooth then, but this afternoon the fuse went off again, so i think, there´s still a problem...

i ran out of fuses and have to get another pack tomorrow.

thanks for your input!

have a nice evening!

jens