[solderon29]

Back in the “dark and distant past”,the power supplies in these Beomaster’s used to spontaneously combust.

The protection system was dubbed “crowbar”,as it had a similar action to dropping a crowbar across the supply outputs and blowing the fuses(and how!)

Even when the product was current (‘seventies) it was notorious for this,and B&O came up with a modification.I used to have a copy of the mod sheet,but can no longer find it alas!

Does anyone else remember this malady,and perhaps have the info to hand,to refesh my old noggin?

Thanks,

Nick

[Dillen]

Are you thinking about the wrong types of transistors fitted as 5TR4, 5TR5 and 5TR6 in the safety circuit?
They can cause the primary fuse to blow for no apparent reason and are found in
some Beomaster 2200 with serial number earlier than 1470001.
Servicemanuals give out wrong part numbers as well.

5TR4 should be a 8320408 (BC 256 or similar)
5TR5 and 5TR6 should be 8320409 (BC 174 or similar).

Martin

[solderon29]

Thanks Martin.

I was’nt aware of that,and it’s “food for thought”indeed.

The crowbar “safety” circuit was a terrible idea imho,and as you say,it could often trigger for no reason.The Beomaster 1500 was also afflicted with this,but it was’nt such a problem as in the ‘2200.

B&O came up with several solutions,which did in fairness improve the reliability of what was and still is an innovative and nice sounding unit.

If anyone has one languishing in their “round tuit” corner,I’d be interested in taking it off your hands,to tinker with.

Nick

Nick

[Author]

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