A Pair of Beomaster 1900 Receivers for Restoration: Unit #2 Reassembly and Power Supply Checks

This second Beomaster 1900 unit is ready for reassembly and its initial power supply checks.

I put the power transistor heatsinks back in place on the four output transistors. I used Sil-Pad insulators for the thermal insulation material.

As a reminder, here is what the power transistors looked like at the start...prior to the capacitor replacements.

Here they are now after the restoration.  Installed with their new thermal insulation.

This photo shows the trace side mounting of the heatsinks.

While I had the heatsinks installed and the Beomaster 1900 turned over I soldered on some test leads for the No-Load Currrent measurements I will be adjusting later.

Next is the reassembly of the indicator lamp boards. I use dual LED lamp assemblies for the Bass, Treble and Balance slider position indicators.  For everything else I use replacement incandescent lamps.

While access is easy to the Beomaster 1900 touch button posts I cleaned the posts and treated them with Deoxit.

I had to resolder the power transformer secondary wires that supply the Beomaster 1900 +15VDC power supply.  That is because I intentionally desoldered them to protect them while I was moving the board around during the capacitor replacment.

Power could now be applied to the Beomaster and the standby lamp indicates there is +15 VDC power.

I tested and adjusted the Beomaster +15 VDC supply voltage per the service manual first.

The voltage coming in from the transformer secondary was the usual voltage of over 22 VDC.

I then performed the service manual adjustment to set the regulated +15 VDC supply to +15.0 VDC.

Next I did a quick check to verify the +-31 VDC rail voltages were present...and they were.

The power supplies look good so it is on to making an initial No-Load Current adjustment.

Per the service manual I adjusted the no load current for the output amplifier emitter resistors where the DC voltage across the emitter resistors is 12mVDC.  That measurement is also made without any speakers connected (no load) and with the volume level at zero.

This is a good start to the Beomaster 1900 restoration wrap-up.
Tomorrow I will finish the service manual checks and run some performance checks.