Pioneer SX-750 won't power on

[49erFaithful]

Hi everyone,

I recently got a non-working Pioneer SX750 in a trade. I'm just starting to try and work on these things so please forgive some of my ignorance or lack of technical terms.

The unit wouldn't power on at all when I got it. No relay clicks or anything. I took the bottom panel off and confirmed continuity in all of the fuses. However, I did notice that I I wasn't getting full voltage to the main fuse. In fact, I'm not getting any voltage reading on the two posts on either side of the main fuse.

Where the power cord comes into the receiver, the hot line and ground split and are soldered onto two posts. I thought that the old cord may have been the problem, so I replaced it, but I'm still getting the same readings. I'm getting about 20 volts on the hot line post, but that's it. And it obviously isn't enough to get the unit to power on.

I'll post some pictures to show you what I'm working with. Any advice would be great. Not sure what to check next.

 

[49erFaithful]

Ok, this is where the cord comes into the bottom of the receiver. I'm measuring about 20 volts on the post with the orange wire, but nothing on the other posts.

This is where the orange wire goes from the first pic to the power switch.



I'm not getting any voltage readings on either post on the sides of the fuse with the yellow wires.

 

[49erFaithful]

Oh, and first step of troubleshooting aside. I was getting readings of 120 volts on the cord end and at the outlet before the cord was soldered back in.

 

[petehall347]

hot line and ground ? its 2 core so should be hot and neutral

 

[llwhtt]

Unplug the receiver, put your meter in Ohms mode, turn the receiver on and measure across the power cord end, should have low Ohms if the fuse, power switch, and power transformer are good.

Craig

 

[Tom B]

Are you getting 120v "AC" across the 2 power leads??
With the new power cord you should.
plug out power cord from outlet and ohm out the power switch contacts. You will probably find the to be open causing the problem. This is a fairly common problem with those units. You can either replace the switch, but they arent easy to find, or jump across the switch contacts to get the unit running. An easy work around is to leave the jum[per across the switch, and use a surge protector with on off switch to power on and off.

 

[petehall347]

i have a thing you can try ...
plug a lamp into un-switched outlet .it should light all the time the unit is plugged into the wall ..
then try into switched outlet ..it should light up when unit is switched on . if not the power switch or the wiring is bad ,

 

[tanker 200]

I'd say the power switch also, I have one that's always on, I use a surge protector as suggested by Tom B.

 

[NAD80]

49erFaithful Welcome to AK. You can find the Service Manual, schematic at HiFiEngine.com. Just register and download for free. The power switch could be the culprit. https://www.hifiengine.com/manual_library/pioneer/sx-750.shtml

 

[49erFaithful]

Wow, you guys are awesome!! Thanks for all the responses. I definitely have a few things to try now. I'll update this thread when I can mess with it a little more.

 

[Binkman]

Build a DBT (dim bulb tester) You have two rectifier circuits and a protection circuit.