Beomaster 4400 - Australia Project - Reassembly and Power Check

Since the last update I finished the capacitor replacement tasks on this Beomaster 4400.

In addition to that, I replaced four incandescent lamps for the front panel. Those were the Overload Indicator, Power On and the two Tuning Indicators.

I cleaned the front panel along with applying some Deoxit to the four slide controls - Volume, Bass, Treble and Balance.

I also reattached the Beomaster 4400 heatsink assemblies with new SIL Pad thermal conductive material on the power transistors.

Here are the before and after photos of the IF Section PCB (PC 2).

Next is the Stereo Decoder and Indicator Circuit PCB (PC 3).

Last is the Pre-Amplifier PCB (PC4).

The next few photos show the indicator lamp replacement in the Beomaster 4400.
The front panel indicator lamps consist of a plastic base with contacts for the power wire and ground, a slot for mounting the lamp fixture (onto a bayonet on the front panel) and a socket for a 60ma-80ma lamp.

It takes a bit of patience and care to replace these lamps.

Here is the Overload Indicator lamp.

Here is the Power On lamp.

Here are the two Tuning Indicator lamps.  The flexible wire that connects power to the two lamp fixtures makes removal and insertion a little tricky.

The front panel controls cleaned up good after the Deoxit treatment on the slider controls.

The next two pictures show the Beomaster 4400 with it's circuit boards re-installed.
The photos show the SIL Pad thermal conductive material behind the transistor mounted to the heatsinks.

This is the point during the restoration where I can test that the Beomaster 4400 has electrical power.

I first plugged the Beomaster 4400 to my Dim Bulb with Variac tester.
That allows me to check that there isn't anything shorted that will draw a bunch of power and damage other electrical components.

With the Beomaster 4400 plugged into the tester, I turn the Beomaster on, then start applying AC with the variac.  I monitor the current draw of the Beomaster as well as the light bulb of the tester to see if any problems begin to appear.  That allows me to stop and shut power down if I see the beginnings of a problem.

The Beomaster 4400 powered up clean without any issues.

Assured that no shorts exist I plugged the Beomaster 4400 into a normal AC socket.

My first step was to check the power supply voltages.  I measured the +15 VDC voltage regulator output, the +35 VDC supply, the two +24 VDC, +33 VDC, -12 VDC supplies and the +-35 VDC rail voltages for the power amplifier.

Here is the +15 VDC check

Transistors 5TR3 and 5TR4 regulate +24 VDC to the Right channel tone controls and Left channel tone controls respectively.

There is a 35 VDC regulated voltage to the IF Section (PC 2).

After the the Beomaster 4400 volume and tone control circuits the there is a Bessel Filter circuit just prior to the output amplifier.  That circuit uses a -12 VDC reference voltage.

The output amplifier circuits have rail voltages of +-35 VDC.

The last voltage check I made was the 33 VDC regulator circuit on the preamplifier board.

The voltage checks were all good so I performed the No-Load Current Adjustment for the Left and Right channels.  The service manual says to adjust the respective channel trimmers for 10mV to 15mV across each channel's emitter resistors.  For now I set them to 10mV.

This Beomaster 4400 is ready for some performance testing.  I will setup some of those tests for the next post.