We’ve just completed a tally of our repair statistics for 2002 and out of 48 “microprocessor problems” only 1 machine required a new micro. The other 47 only had reset circuit problems. Just last week Dr. Gil Stein sent in a Beomaster 5000 with no response from the front panel. Turns out this machine had a 33ufd capacitor collapse and the reset pulse wasn’t being sent to the micro.

A fellow in Seattle contacted us in March 2003 about the possibility of Beomuse having a micro for sale in regard to the Beomaster 6000. We did but we felt that it would be a good idea for his machine to come in for service and verify the need for a micro. Nope… reset circuit, and very common in the Beomaster 6000. The adjusting pot can get dirty and the reset pulse won’t be seen.

I suppose the lesson here is very clear. Just because data pulses aren’t there doesn’t necessarily mean that a micro is bad. Our experience has shown that B&O micros are very tough. The reset circuitry, just as in many other brands of equipment, is prone to failure.

What is a reset circuit? Just about any microprocessor requires a “suspended operation” mode when 5 volt logic signals are building up when a machine is first plugged into the AC. It takes a tiny fraction of a second for a proper 5 volt system to get stable. If the micro is booted up during this charging period strange things can happen. The reset pin of the micro is basically a “hold your horses” command for a predetermined amount of time so that the 5 volt system can stabilize. After this period the reset pin is activated and bootup is started. There are many ways to create a reset circuit and B&O has quite a few different means to achieve this for any given machine.

Capacitors will always be an issue here. Capacitors get old and they start to “leak”, either literally or figuratively. A pot in a reset circuit is no different than those in amplifier offset and idle adjusting circuits… they’ll go bad someway or another down the road.

Of grave concern is the 5 volt power system itself. A bad 5 volt system can wreak havoc with a micro. That’s why any machine coming into Beomuse for repair (if it has a micro) gets a full test of the 5 volt system. Micros are getting rare for various machines.

As always, use a TrippLite Isobar or equivalent device to protect your fine Danish investment!

© Copyright Anthony Garza, used with permission.