Thursday, July 23, 2015

Pioneer SX-550 Receiver

Pioneer SX-550 Receiver

Here we've got a nice Pioneer SX-550 in for a restoration. The unit came in quite dirty from typical wear and tear and the faceplate, quite the build up on the plate and knobs. I was extremely happy with how clean the knobs the plate came out, night and day from when the unit was dropped off. 

Power Supply
The single assemblage PCB here plants the driver, tone and power supply all in one location. The power supply utilizes two 6800 microfarad capacitors in the rectification/driver filtering. This does use an interesting secondary in-line fuse array for protection as well. All capacitors here were upgraded with high temp long life panasonic FC/FR capacitors, general use diodes were replaced 
with modern UF4XXX series. The filter capacitors were replaced with 6800 microfarad Cornells.

The RIAA consists of dual 7136 pick-up IC's, all electrolytics including small value tantalums were replaced with audio grade Nichicons and low impedance high reliability Nichicon PW's. Whats interesting in this topography is the attention in design to hi/low gain loss typical here and how they compensated in pre-amplication. 

Driver Assembly
The amplifier circuit consists of a pair of dual FET differential transistors in the 1St stage. In the final stage I want to highlight a upgrade that may be of some benefit for continued years of use, updating the output devices to a more reliable TIP41/42 TO-220 transistor package (2SB596/2SD526). The biasing procedure is effortless with easy to access (cept #36) "test points". For all electrolytics here Nichicon KA and KW audio grades and WIMA PP's were utilized.

RF (AM/FM) stages
Per my usual I think the Nichicon PW's really work great here, a nice reliable low impedance capacitor. Several tantalum capacitors in odd ball values are present and should be updated with electrolytics as well. 

New 8V 300mA lamps and a deep cleaning wraps it up, a very nice little side setup receiver.

No comments:

Post a Comment