Today were showcasing a few special repairs we had come in from a customer who stayed in the area over night from out of state.
The Pioneer SX-1050 is a fantastic receiver, though has some typical SX series heat issues on the driver assembly as well as the original 1439 devices which have a high failure rate. This unit came in with an intermittent loud static after use that would pop in the outputs.
Further diagnostics revealed a failing BJT (2SA750 w/ leakage RFdV) within the driver network and a stressed electrolytic tied in. Because of the heat issues and populated 1439 devices both channel were symmetrically rebuilt.
All of the electrolytics were replaced with a KT audio grade and low impedance high temp (105C) PW Nichicon capacitors with an increase in operating voltages, also the input .68 films were upgraded to high grade WIMA polypropylene films. The bias potentiometers were replaced due to the caustic glue near the molex and several heat battered resistors replaced (18K near the current limiting resistors.
New matched differential pair TO-92 low noise fairchild and new Fairchild TO-126 modern transistors were installed up to the 3rd order driver pairs.
New LED's to finish her off
The Marantz 2215B is one of the smallest entry levels Marantz receivers produced, this being the latter B version. The 2215 is a fantastic small wattage output receiver with the prototypical warm Marantz tone and presentation.
This unit came in from a failed repair attempt by another. The driver assembly had suffered significant damage shorting several output devices. As the unit came in major re-work was necessary to repair the repair attempts and then the assembly. One of the outputs was still shorted along with the thermally coupled bias transistors and the right pre-drivers had evident leakage current.
As a precaution the board was limited-re worked. 100MFD to 10MFd electrolytic were replaced with KT audio grade and low impedance high temp (105C) PW Nichicon capacitors with an increase in operating voltages. 1MFD electrolytic were replaced with high grade WIMA polypropylene film capacitors. A new MJ On Semi PNP TO-220 output device installed, new bias transistors and pre-driver transistors with modern low noise Fairchild TO-92 transistors. New shorted resistors were replaced with KOA 1/2 carbon film type.