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Sunday, July 15, 2018

Beomaster 4400 (2419): PC5 Recap

Today I tackled the large PC5 board. The service manual titles it the AF Amplifier, Power Supply, Muting and Silent Tuning board. I'll often refer to it as the PC5 board, main board or output amplifier board.

The PC5 board has the most electrolytic capacitors to replace and it has six trimmer resistors.

Here is a picture of the board before recapping.

Beomaster top opened up

Boards and reservoir capacitors removed

Since this board is the largest and kind of difficult to remove for recapping I will take the opportunity to measure the output transistors (the ones mounted to the heatsink). I will also check and reflow solder joints on the board to board wires and the output amplifier transistors.

The transistors measured good but there were a couple of bad solder joints where the transistors attach to the PC5 board.

The recapping of this board takes a while as it has quite a few capacitors. There are a lot of 1uF, 2.2uF and 4.7uF capacitors. I think this particular Beomaster may have set a new personal record for the number of out of tolerance capacitors found. I found 1uF capacitors measuring as high as 4uF.

Here is the recapped PC5 board.

Tomorrow I will install the new reservoir capacitors and this Beomaster will be about ready to try out.

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