No, you won't blow anything with LED's but many functions rely on the current
flow through the lamps.
The green tuning arrows would not work/indicate correctly.
The volume control could become erratic and/or unstable and the three tonecontrol
lamps form part of the 15V supply circuit in that their current draw is used
to drain the 15V when going into standby - a too low current draw would see
the Beomaster hard to set into standby, it would pop back on again with a series
of clicks if the pad was kept activated.
The source lamps are often critical in that the Beomaster typically refuses to
either change to - or change away from - a source where the lamp has an
incorrect wattage.
Symptoms can vary slightly from machine to machine but this is the general picture.
LED's were available when the BM1900/2400 was designed and built. One LED is
actually used.
LED's are nothing but hard working diodes.
They fail just like any other semiconductor and I've replaced about 7 or 8 standby LED's in
Beomaster 1900/2400's by now.
If B&O could have used LED's for this futuristic wonder of
a stereo receiver, they would have used real 7-segment LED displays instead of lamps behind
screens made to look like 7-segment LED displays.
New lamps of a good quality will last for years and it will look, feel and function
as the designer and engineers intended.
Others may not agree. Some modern repairers try to fit LED's in wherever possible, expecting them
to last forever.
You are free to make you own experience if you absolutely must customize something.
The above is mine, based on 35 years with B&O things.
Martin