Anyone any ideas as to why my BM 5500 will automatically shut off as soon as I turn the volume level up to 28.....

It does not matter what input - radio, aux, CD but it just switches off as soon as the volume level reaches 28!

ANY opinions welcomed!!!

B

That's a common fault on the BM5000/5500/6500/7000. They all have 2 potentiometer (R126+R226) on the poweramp. After 20 years they fail because of age, dust... smoking ;)

Replace them by new 100 Ohm high quality Potis and adjust the NoLoadCurrent to 11mV in total measured over the 2 resistors R128/129 or R228/229.

Your NoLoadCurrent is to high and causes a failsave power cutoff.

Martin 

P.S.: Cleaning is possible. Turn them several times from one end to the other, mark the original position before !!! ... or make the adjustment 11mV...

Use "Balance" to determine, which channel is defect. 

 Martin,

Thank you very much.   I do not smoke but we do have dust and age against us!

Is there a circuit diagram to help me locate these potentiometers?

Brian

Look here:

 [img=http://img120.imageshack.us/img120/7016/noloadto5.png]

 http://img120.imageshack.us/img120/7016/noloadto5.png

Martin

Thank you very much!

Brian

I am looking to buy these from Farnell - but there are some 198 potentiometers !  Do you have any more details of what I should be looking for beyond good quality 100 Ohm?

Voltage rating, element type, tolerance, make - for example

http://cpc.farnell.com/jsp/search/browse.jsp?N=411+1003242+500001

I have been looking at the above link and am hopelessly lost!

Brian

Something like that is good enough. It should be capsuled and resist against dust and smoke.

http://www.reichelt.de/?;ACTION=3;LA=2;GROUP=B212;GROUPID=3127;ARTICLE=14619;START=0;SORT=artnr;OFFSET=16;SID=278upq4awQARsAABt7JDQ958145b8daefb9aac00d2d0973afc559

It is a sign that it takes to much current when you turn up the volume. The protection circuit gives a signal to the processor unit to shut down. It could be that one of the pairs IC 400- IC401 or IC 200 - IC 201 are bad. This may show by the large heat sink getting warmer than usual.