Canada Beomaster 8000: Power Check Milestone Reached

I mentioned in the last post on this Beomaster 8000 from Canada restoration that my next step was to check the restoration work so far by performing some power checks. That means connecting up all of the boards, plugging the Beomaster power plug in and checking the DC supply voltages.

That milestone has now been reached. Plugging in the Beomaster yielded no surprises and the expected red dot standby LED illuminated.

Pressing the PH (phono) button on the control panel illuminated the volume level and PH segments on the display.

The Beomaster appears to have power so it is time to measure the DC supply voltages.

First is the +5 VDC supply reservoir and the output of the +5 VDC regulator.

Very good. That check was pretty much redundant as the red LED dot would not have illuminated if the +5 VDC supply wasn't working. But I like to see what the actual voltage is.

Next are the ±15 VDC supply reservoirs and voltage regulators.

Those all check out. Now for the ±55 VDC rail voltages for the left and right channel output amplifiers.

All voltages are present and accounted for. That is a major milestone in the Beomaster 8000 restoration. From here it is to return and complete the work on the microcomputer and display boards.  After that I will reassemble the Beomaster 8000 for functional testing.

With the power applied to the Beomaster I was able to see that there are some failed display segments. The plan was to rebuild those displays anyway so that confirms it is necessary.

Beomaster 8000 - First Inspection

I bought a 4th Beomaster 8000 recently on ebay. It was listed with the usual "nothing happens when I plug it in, probably the fuse needs replacement" statements, which deterred many bidders, i.e. I got it fairly cheap. Externally it is pretty good, making it a worthwhile (my wife appears to have a different definition of 'worthwhile'...;-) project.

Today I finally got around to looking into it. A first look at the fuses on board 7 indeed revealed a blown 10A fuse (F2). F3 was o.k. This immediately suggested that probably one of the output stages burned out due to a non-contact quiet current trimmer.

I opened the Beomaster up and disconnected the power to the output amplifiers (red and black leads that connect to the boards via tabs) securing the plugs with some tape to prevent them from making accidental contact when the power is on. Then I replaced the fuse with the proper 10A quick acting type and plugged the Beomaster in. A good sign: the decimal point LED in the volume display came on, while nothing else happened.

Then I tapped one of the radio preset buttons. The Beomaster came alive, but showed strange displays:

The volume came on at 6.0, i.e. full throttle. I reset it to 2.0 with the volume store button, which seemed to work with the usual blinking of the display during the storing process. We will see if this fix is permanent or if there is some problem. The frequency display showed a local station, i.e. the radio might be o.k. Turning the rotary encoders showed that these two displays are o.k. w/o missing segments...a rarity. The other two displays showed garbage. Usually one would think that some segments are dead. However the perfect performance of the other two displays suggests that there is a deeper lying problem needing further investigation. Let the fun begin!