Pioneer SX-1250 Re-Cap and Restoration
So now I know what all the fuss is about with these beastly Pioneers
I bought this 1250 as an As-Is/Non-Working unit. It was in very good cosmetic condition, otherwise I wouldn't have bothered. There was a water stain on the wood case and also a residue on the bottom plate. It looks like someone spilled a cup of hot chocolate or orange juice right into one of the amp boards.
Surprisingly all of the fuses were intact, so I turned it on with a dim bulb tester and when there was no short indicated, fired it up. The lamps lit up, the relay clicked and I had music, but in one channel only.
I used MarktheFixer's BOM from August 2013 with a couple adjustments per Echowar's recommendation. About 213 components were replaced and the work took about 40 hours.
Two boards were problematic. About a third of the solder foils on the relay board partially disintegrated upon de-soldering. I had to improvise by exposing copper traces or extending leads to nearby solder pads. 70% of the solder joints in the stabilizer board were bad (not surprising considering how hot the right side gets). All of the solder joints were either replaced or re-flowed. This took some time since I examined each joint at least 5 times at different angles with a 4x loupe.
The other boards were easy to work with and as everyone notices, the build quality is absolutely top notch.
Not included in the 40 hours of work time was 5 hours spent troubleshooting a ground-related hum. I looked for shorts in ground wires, soldered sketchy looking wire-wrapped pins, and sanded oxidation from ground-chassis connections. Nothing worked... until I changed the source. Bingo! It was the DAC.
The work is not finished however, there is a mild hiss in the pre-amp. When the tone defeat switch is engaged the background is dead quiet. I suspect there are a few bad resistors. I measured some and quite a few were out of spec, but it's hard to know for sure unless the resistor is removed from the circuit. So, I will replace all of the carbon film resistors in the two main pre-amp boards with 1% metal films and also upgrade the film caps. The BOM was also short 2 transistors and 1 electrolytic which will have to be replaced. A heatsink will also be added to the regulators on the stabilizer board, an Echowars recommendation.
I bought the unit for $250 + $95 shipping and parts were $270, so my cost so far is $615.
So how does it sound?
Well, I had my HE-4 listed for sale, but after I took a short listen, I ended the listing. I think it was Matt who said in a previous post that the HE-4 only came alive after it was hooked up to some massive raw power. I'd agree completely. It sounds so much better than out of the Marantz 2270 (HPO).
Slightly warm, detailed, big soundstage and seemingly unlimited power on tap
So far the only negative is that my back hurt for 2 days after carrying it from my office to the living room
