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Monday, March 4, 2019

Beomaster 1900 Type 2904: Cleaning, polishing and reassembly

For about a week since the last post this Beomaster 1900 has been sitting on the workbench playing music for hours on end. No problems surfaced during that time so with the new parts broken in I am ready to reassemble the Beomaster before going into the final stretch of testing.

The trickiest part of the reassembly has to be the touch control panel.
The copper, spring leads for the touch controls must fit onto corresponding posts on the Beomaster 1900 circuit boards. A trick Martin Olsen taught me was to install this panel with the Beomaster 1900 bottom cabinet plate still removed. That way you can inspect each touch control contact from underneath and use some tweezers or probe to maneuver the contacts into place.

I reinstalled the indicator masks for the bass, treble and balance slide controls at this time.
I also used some plastic cleaner and aluminum cleaner on the touch panel as I installed it.

The next piece to install is the other part of the top cover. The grooved section for the heatsinks and the access door hinge had a lot of dirt and grime from wherever this Beomaster was stored.

I cleaned it with mild cleaning solution and a couple of brushes to get into the channels.
The right side hinge of the access door was loose and came off so I reattached it with some epoxy.
Before reinstalling the base of the cabinet I gave the Beomaster a quick test to make sure all of the electrical connections were still good.

Finally I could install the cabinet base. This cabinet was missing all four of its feet so I used the replacement feet I recently got from Martin Olsen.

While the Beomaster 1900 was upside down I noticed that the Phono DIN jack is a 7-pin DIN connector.  There isn't anything wrong with that but the Beomaster 1900 will never utilize the number 6 and 7 pins of that connector. The Beomaster 2400 is the receiver with a remote control and can control Play/Stop functions of a Beogram 4004 via the 7-pin DIN. Except for the remote control the Beomaster 1900 and 2400 share the same circuit board so I guess Bang & Olufsen just started installing the same source connectors on both receiver models.

The Beomaster 1900 is all assembled again so I turned it over and started another play test session.

This week I will connect it up to my audio analyzer and make some measurements. After that I will hook it up to a Beogram and Beocord to round out the functional testing.

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