The shiny metal plate next to the circuit board is the heat sink for the power semiconductors in this unit. Can you see these? These are still electrically OK but will fail soon. While we’re at it, let’s look for other failed joints. This one is at the DC common point of the amplifier. Here is another failed joint undergoing rework. Rosin activated flux was added and the old solder removed. The solder fillets are OK but the mechanical joint failed entirely. This is the other side of the circuit board. This kind of solder is brittle, so solder joints made with lead-free solder often fail from cracking stress. The solder used in this unit is ‘lead-free’ and compliant with RoHS, the directive to remove harmful substances from the supply chain. The flag terminal came off the main circuit board. These come off now and are stored with the knobs lest they fall off and get lost on their own.ĭo you see what I see? This white wire carries the AC power neutral to the main circuit board. Note the white nylon spacers on the jacks to the right and the inside-toothed lockwasher on the rotary encoder to the left. The circuit board is separated from the front panel of the chassis. If you ever venture here, beware! TIP – slip a thin scraper or putty knife between the chassis and the cabinet to keep this from happening. The captive nuts in the chassis have sharp corners on them, which snag the Tolex covering that wraps inside the enclosure. The screws that hold the chassis in the chassis come in from the sides of the enclosure. This needs to be right when reassembling the unit!Īnd the one on the right is the ” + ” terminal. This picture documents the wiring polarity on the main driver coil. The unit appears to be completely dead, with power present at the fuse holder. Could the Unbrokenstring Crew make it right? Mysteriously, this modern Ampeg bass combo amp quit working.
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