A Pair of Beomaster 1900 Receivers for Restoration: Recapping the Main Board and Volume Control Board (Unit #1)

The restoration work on the main board and on the volume control board is now complete.

The Beomaster 1900 and 2400 receivers are low profile so they look small. I always start out these restorations thinking that it should be easy...but once I get started on the capacitor replacement I am quickly reminded at how many components there are.

Here is the main board as I received it.

Here is the main board after replacing the electrolytic and tantalum capacitors.

Here are some details.

As I like to do, I replace the electrolytic and tantalum capacitors that have values 4.7uF and smaller with WIMA MKS capacitors. Those are the capacitors that look like red rectangles. They are non-polarized capacitors as well.

For capacitance values higher than 4.7uF I use high quality 105°C rated capacitors.

I always try to match the original capacitor's voltage rating.

Just like I have seen in the other Beomaster 1900/2400 units I have recapped, most of the capacitors are out of tolerance by 30% to over 100%.

I always measure all of the capacitors I remove. I won't post every photo but these two give you an idea of what is typically found.

This is an original 220uF capacitor...a little out of tolerance now.

Here is a 2.2uF capacitor.

The new, replacements will make a big difference with the old capacitors being so far out of tolerance.

Here is the new 220uF capacitor, a Nichicon.

The only capacitor I didn't change out was a 10uF tantalum capacitor inside the FM tuner. I did take it out and measure it...it was right on 10uF so I decided to leave it in place.

This first Beomaster 1900 unit had some past issue with the rectifier bridge for its +15 VDC voltage power supply you might recall.

I decided to replace the pieced together rectifier bridge with a single bridge device.  I also decided to replace the previously replaced capacitors. They still measured good but I want to start with all new electrolytic capacitors.

The two large reservoir capacitors for the output amplifier voltage rails are typically still within tolerance. The two on this Beomaster were as well but I replaced them anyway due to the effort it takes to change them out. I don't want to have to come back and do them later.

Here are the original two reservoir capacitors.

Here are the new ones.

While working on the main board restoration I decided that I didn't like the looks of the way that the +15 VDC regulator device was mounted. The thermal past looked dried out and it would bother me to know that was in there like that.

I reworked the mounting of the regulator by cleaning off the old, dry paste and remounting the regulator with a SIL-Pad.

That looks better. Note that I also added some hot glue to help support the 2200uF capacitor for the +15 VDC supply.

One more change that I made to the main board was to replace the left and right channel 250Ω trimmers (for the output amplifiers' no load current adjustment) with new, sealed, multi-turn type trimmers.

That took care of the main board.
The Volume Control Board was next.

Here is the before photo.

Here is the after recapping photo.

This shows the Volume Control Board reinstalled.

So far the restoration work has meant the removal and replacement of sixty-four capacitors, two trimmers and the four diodes of the bridge rectifier.

This photo shows the removed parts.

I will have to do all of this again for the second Beomaster 1900 receiver.

There are still the tasks of the Tone Control/FM Tuner board recapping as well as the replacement of the Beomaster 1900 indicator lamps.  Once those tasks are complete I can start testing this receiver...the fun part.