Marshall^® DSL100  •  Tube Socket PC Board

To rework the underside of the Marshall DSL100's Tube PC Board, the board has to be detached from the chassis.

First, remove two brass screws beside each of the power-tube sockets.  In this photo, six of the eight screws have been removed.

On the inside of the chassis, remove six silver screws holding down the PC board.

In this photo, red tape points out three of the six PC-board mounting screws.

The Tube PC board is now loose.  You needn't disconnect every cable from it, just enough to turn it over.  Most solder points and circuitry are on the hidden side.

On the right, red tape marks the 7-Watt, 270-Ohm resistor that will be replaced by a choke.  The resistor is designated as either R63 or R71.

Here, R71 has been unsoldered and removed.  Wire leads have been soldered in its place.

Power-supply chokes, also known as inductors or auto-transformers, can improve the performance of power amps.

In this photo, a purple dot marks C17, sometimes designated C12.  This is the treble-bleed capacitor affecting the tone of the Red-LED Overdrive channel.

The capacitance of the original bleed capacitor is 470 picofarads (pF).  The owner of this amplifier had the cap. replaced with a 120 pF value.

People sometimes snip out parts like R71 or C17 instead of turning over the board and properly desoldering them.  This isn't always a great idea if you want to solder in a new part.

That's because there's unseen solder on the board's other side.  In this photo, purple dots mark the solder points of C17.

When soldering from above, this solder can melt and drip off the circuit foil, leaving a weak connection.  Too much solder can also drop down and cause a short circuit to the chassis.

So now is the time to make any changes to the Tube PC board.  Then reinstall it before continuing on with the choke installation.

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