SX-5590 (SX-1250) Project

[Wyatt Weeks]

Looking for some general advice on this project:



If you don't want the background, skip this paragraph. I thought I was done rebuilding receivers after rebuilding my SX-1050 (thread), but I was innocently browsing FB marketplace one day and found a newly listed SX-5590 in my area. I went to look at it and it was cosmetically perfect and was being sold by the granddaughter whose grandfather had bought it overseas in the service. Functionally, when hooked up to the HPM-100's that she was also selling (I didn't buy - couldn't afford both!) there was a little scratchyness in a few of the controls, but that was it, she was working. I bought it and paid real money for it, but got a good deal I think. I got it home and hooked it up to my Yamaha NS-890's (Japan only model - non-monitor version of the NS-1000's) and it sounds great. worked the controls several times and the scratchiness went away. the only issue I could detect was some clipping in the left channel when approaching 12'oclock on the volume knob, which is LOUD! so I listened and thought for a few weeks about what I was going to do with it. I decided I was going to at least do the protection board and the power supply boards. But I'm a little rusty, as it's been a couple of years since I've been in a unit. So I decided I'm gonna do an sx-737 to warm up. I'm no pro and just began teaching myself how to do this right before COVID. I've rebuilt probably 8 or 9 pioneer SX units. Then, I ordered a kit from Ben via that big auction site. not cheap, but as I found, worth the time savings in coming up with a BOM myself, and the kit was super complete and thorough. Using the instructions he includes, I barely even referenced the service manual or any mouser data sheets while doing the rebuild. the sx-737 rebuild turned out nicely and I gave it to my brother for Christmas.

So, back to the SX-5590... I decided to tear into it. IBest I can tell, first time any of the screws were even removed from the unit. Totally original inside. I checked PS voltages and rebuilt the two PS boards and the protection board - stopping and testing and getting voltages between boards. They changed little. I used Ben's kit for the sx-1250 and it's been spot on so-far. Here's what I ended up with (PS voltages):
Pin Volts
1 48.4 VAC
2 48.4. VAC
3. 68.4 VAC
4. 68.4. VAC
5 19.4. VAC
6 19.4. VAC
7. 0
8 23.5. VDC
9 85.7. VDC
10 -87.5 VDC
11 8.1 VAC
12. 8.1. VAC
13. 35.3. VDC



So I'm really thinking about replacing the filter caps and leaving the rest of this unit alone. (though I'm not looking forward to tackling the different screw size problem on the big blue filter caps). This unit is so clean and probably used relatively little, that I question myself in what kind of benefits I'd really get from doing the rest of the boards. What would you guys do if this were your own personal 'grail' unit (especially those of you that have serviced a 1250 or two) ? Would you button it up and leave the rest alone, or continue and install the rest of the kit? Thanks in advance for any advice.

 

[Wyatt Weeks]

When setting the power amps and stabilizer voltages, do you guys recommend removing the pre-out/power in jumpers and inserting 5.1k resistors like the service manual describes? or do you just set voltages with the jumper plugs in place? Does it matter?

 

[zebulon1]

I like to remove the jumpers when setting the amp trimmers for the bias and DC Balance.
no resistors are needed.
No volume and Balance knob at the center point. That's all you need for setup.
Remember to reinstall the jumpers after you get the amps sorted.

 

[Wyatt Weeks]

Thanks @zebulan1! ...For what it's worth, I remeasured after removing the jumpers (since I'd kept the jumpers in when I dialed it in the first time), and after the 10 minute warmup, I got <+/-1mV difference readings on the factory recommended 100mV settings on my Fluke 117 vs. when I had the jumpers in. So, at least on my unit, I'm not sure that the resistors OR removing the jumpers matter much. wonder why they added those steps in the service manual...

 

[Wyatt Weeks]

Am I understanding correctly that the recommendation is to clean the Volume pot with F5 and the rest of the switch and knobs with D5? So no D5 in the volume pot?

 

[kwayde]

Am I understanding correctly that the recommendation is to clean the Volume pot with F5 and the rest of the switch and knobs with D5? So no D5 in the volume pot?

I use F5 on any resistive controls like volume, balance, bass, and treble because it has a little more lube in it.

I use D5 on switches that have metal to metal contact like push button switches, lever switches, switches with rotating contacts on wafers, etc. I use CRC QD Electronic Cleaner more than D5 because it evaporates fast.

Don't use it on knobs. I use soapy water for those most of the time.

 

[Wyatt Weeks]

Thanks kwayde!

 

[Wyatt Weeks]

overall update on the project: rebuilt the protection, power supplies, and amp boards. replaced the filter caps. I think I'm going to clean the controls then button it up for now. maybe to rebuild the flat amp, phono, and control amp boards in the future. Going to listen to for awhile first.

 

[Wyatt Weeks]

Is cleaning controls on this unit effective from the front (with faceplate off obviously and mounting nuts removed)? Or do you really have to go in from the board side to get a good clean? I'm not having any issues with the controls, but want to proactively lube.

 

[kwayde]

To clean controls disassembly is required.
I've only been into one SX-5590.