My restored SX-1980

Friday, February 28, 2014

Pioneer SX-5590 recap and restore (beauty shots added!)

I recently got in a Pioneer SX-5590 to recap and restore, the thing is in excellent condition overall, case, top grill and faceplate are almost immaculate. I'm using the Panasonic FM and FC series for the audio path caps, Nichicon KL series for the orange low leakage caps, Nichicon PW series for the power supply, stabilizer and protection boards, Nichicon VX series for the axial caps and Panasonic ECQ poly films for caps under 1uF. The owner asked me to go through it and give it the works, so here are the results!

Before photos:

Receiver on the bench:

EQ amp:

Flat amp:

Tone amp. This one had a broken pot for the 10KHz adjustment, so I'll be replacing that.

New pot installed, old pot out:

Filter amp:

Power supply:

Left power amp:

I did not get a pic of the right power amp. I thought I had it, but when I reviewed the photos, I found that it was nowhere to be found! Oops. It is however very similar to the left power amp.

Protection board:

There was a tech in here before me and replaced several things on the stabilizer board along with one on this board. It is C6, a 100uF 50v cap and they replaced it with a 68uF 100v cap. Huh? The stabilizer board is even more interesting.

Stabilizer board. This board is by far the worst off, a lot of heat stress and the previous tech did a mash-up of weird cap brands when they replaced the original caps, which, judging from the rest of the components and the board, likely had bad heat stress and dried out. They also replaced a few transistors and one diode with questionable replacements.

Weird cap brands, I've never heard of these except for the green Samsung caps.

The back of the board shows a lot of heat stress to the solder joints as well, several cracked joints along with the previous tech's work being a little sloppy, they didn't clean the flux off and the joints look cold.

And now for the after photos!

EQ amp, 12 caps and 14 transistors were replaced. Four transistors near the big red poly caps, the two on each side in a horizontal configuration are differential pairs and were gain matched. This isn't a critical step and won't mess up the amp if you don't do it, but it does help with the balance and overall sound in my experience.

Flat amp, 12 caps and 6 transistors were replaced.

Tone amp, 26 caps and 4 transistors were replaced along with the 10KHz adjustment pot.

Filter amp, 4 caps and 2 transistors were replaced.

Power supply, 4 caps were replaced and all the fuses were checked for proper rating and condition.

Left power amp, 5 caps and 3 transistors were replaced on this board, the differential pair and the overcurrent sensor, Q11. Also replaced were the 2 trim pots, the solder joints were touched up and the pins for the outputs at the top of the board and the pins at the bottom were cleaned. The differential pair were gain matched, but again, not a critical step and it won't blow up the amp if you don't do this. Gain matching simply helps the offset adjustment balance better

Right power amp, same thing as the left amp.

Protection board, 6 caps and 3 transistors were replaced along with the relay, the 3 transistors were all upgraded with bigger case styles to help with heat dissipation and longevity. Also touched up the solder joints and cleaned the pins.

Stabilizer board, it looks sooo much better now. 16 caps, 13 transistors, 6 diodes and 2 trim pots were replaced. Several of the transistors also were upgraded with bigger cases for better heat dissipation. New micas and thermal paste was applied for the regulator transistors on the heatsinks, the pins were cleaned and pretty much all the solder joints were cleaned of the old solder and re-soldered.

With the de-soldering and soldering comes a lot of flux, a lot of boards I've come across that were previously worked on do not have this removed. It leads to a cruddy looking board and in the case of a preamp board, can vastly increase the noise floor and crosstalk depending on the type of flux. I always try to clean up all the boards, the results are something like this: (note: this board is a worst case scenario, most don't have quite this much flux on them)

After the cleaning and re-soldering:

I also replaced the filter caps, originals are Nichicon 22000uF 80v, the new ones are NCC 24000uF 100v

Left channel:

Right channel:

Old filter caps:

New vs old:

New filter caps in the clamp:

And after!

Cleaned up the chassis a little as well, here's a few samples:

Before of the left side:

Before of the right side:

And after!

Left side:

Right side

Everything is almost back together!

Top shot:

I replaced all the lamps with LED's. Take a look!

New LED dial lamp vs old incandescent:

New indicator lamps, LED is on the left, incandescent is on the right. The LED looks almost identical to the incandescent as far as color, but is a lot brighter without being too bright. In person it looks perfect.

Before and after of the dial lamps, the difference is quite startling with the camera, in person the difference is not as big, though the color difference is very real. Note: I had already replaced the indicator lamps with LED's, so that's why they look the same in both shots.


And after with the new LED's:

A total of 156 components along with 13 lamps were replaced. Powered up on the DBT (Dim-Bulb Tester) and checked the bias and offset, bias set perfectly and the offset was within 2mV of zero without adjustment (that's what gain matching does). Turned the bias back down, took it off the DBT and went to full line power. Checked and set the stabilizer voltages, then set the bias and checked the offset, it was still within 2mV of zero. Hooked it up to my Polk SDA-1C's and gave it a trial run. Here is the result:


This thing sounds fabulous! Very clean and balanced sound, amazing soundstage, tight, very well focused and transparency that just makes you sit down and listen with utter pleasure to your music. I could listen to this amp all day through these speakers. It's the same as a 1250, so what you hear with this receiver is pretty much what all 1250's and 5590's sound like once restored. I could never recommend this amp enough, with the right speakers, it is magical.

I'll have some beauty shots coming soon, so stay tuned!

03/02/14: Beauty shots!

And that wraps up this restore! Feel free to leave me comments, questions or criticisms, and if you like this restore post be sure to click that +1 button!