sx-650 relay not clicking

[Anonky]

Hello friends. I just obtained a pioneer sx650 as a repair unit. Was told a "resistor fuse blew." As soon as I got it home, I powered it on (no DBT--shame shame, I might make one soon). All lamps work. Relay clicked. The sound was sizzling a bit but cleared up quickly. Played fine for ~5 mins then the relay disengaged (protection mode?). The unit still powers on fine and the AM/FM section is still catching stations, but the relay is not clicking upon powering up the unit. All lamps still work. I suppose whatever the problem is precedes the relay switch and mostly likely is the in the power amp assembly. On visual inspection I do not see any obviously blown resistors, caps or transistors. No smoke, etc.

I have got the service manual and am reading. I'm not yet fluent at reading schematics. I have a multimeter and understand how to take basic measurements. I'm off work tomorrow and could follow any specific instruction and report back. I've tried to get the power amp assembly out from the bottom to take a better look at the components but it is not wanting to budge after I remove the screws?

Of note, I also have a donor sx650 unit this is in much worse cosmetic condition but at least powers up and relay clicks. I've yet to hook up speakers to it to confirm it functions, but I could potentially transplant any NLA parts if needed. Any pointers or advice is appreciated.

 

[emsrph]

First step...Rule out the power switch as the issue. It’s a problem on this unit and causes bad AC connection.

With the unit unplugged jumper the two terminals of the switch that is on the back of the speaker selector. Plug in and see if problem clears up.

 

[Anonky]

To give a bit more information — After finicking with it a bit more last night, there is definitely some failed or failing component I believe. When I turned the volume up over past 12oclock I started to hear a hissing noise coming from the general area of the amp assembly. I was worried to look in there while this was going on for fear of something blowing up in my face.

anyways what is the best way to jumper the switch exactly? I’ve never done this so it may need to be simplified a bit. I’ve attached a photo of my view of the selector switch from the underside of the unit. It’s a bit tight in that area

First step...Rule out the power switch as the issue. It’s a problem on this unit and causes bad AC connection.

With the unit unplugged jumper the two terminals of the switch that is on the back of the speaker selector. Plug in and see if problem clears up.

 

[kwayde]

If you listen to the area I pointed out in this pic you may hear an arcing sound. These power switches have contacts that arc and destroy themselves. The arrow points to the brown portion of the switch assembly. The brown end is where the contacts are enclosed and just may be the hissing sound you hear.

 

[emsrph]

I would use a wire with alligator clips. Something like this https://www.amazon.com/WGGE-WG-026-Pieces-Colors-Alligator/dp/B06XX25HFX/ref=sr_1_7?crid=3QW3CPI2YANGG&keywords=alligator+clips&qid=1651606461&sprefix=alliga,aps,123&sr=8-7

@kwayde has a good pic and there are also these threads https://www.audiokarma.org/forums/index.php?threads/sx-650-help.95002/#post-972592
https://audiokarma.org/forums/index.php?threads/we-can-rebuild-him-we-have-the-technology.372256/


You may need to take off face plate and remove headphone jack to access the switch. If I recall it should have a yellow and orange wire on the back that are what you jumper for this diagnostic test.

 

[Anonky]

If you listen to the area I pointed out in this pic you may hear an arcing sound. These power switches have contacts that arc and destroy themselves. The arrow points to the brown portion of the switch assembly. The brown end is where the contacts are enclosed and just may be the hissing sound you hear.

View attachment 2556773

It is not from that area I just confirmed. It is definitely coming from either the power amp board 1 or 2. When the volume gets to like 12 o clock or higher it is causing some component to hiss and the relay to cycle in and out of protection mode. The relay will not engage on powering on but only will when I turn the volume up. I can’t quite tell which component is causing the hiss but it only occur when the volume is turned up higher.

EDIT: power assembly 1 or 2 is where it is coming from***

 

[emsrph]

paging a next level tech...

 

[Anonky]

paging a next level tech...

I would like to rule out the switch as part of the problem, like you suggested. Could be the etiology of the failing component downstream. I will read the threads you linked

 

[markthefixer]

"Volume is turned up higher"

Does with or without speakers engaged make a difference?

Does the balance control (full left or full right) make a difference?

Can you see the tops of the small electrolytic caps.
I'm calling the end opposite of where the leads poke out the top - usually it has a line or groove in it so that if the cap wants to pop, those areas are weaker and will open up first at a lower pressure. Hisss not BLOOIE....

 

[Anonky]

"Volume is turned up higher"

Does with or without speakers engaged make a difference?

Does the balance control (full left or full right) make a difference?

Can you see the tops of the small electrolytic caps.
I'm calling the end opposite of where the leads poke out the top - usually it has a line or groove in it so that if the cap wants to pop, those areas are weaker and will open up first at a lower pressure. Hisss not BLOOIE....

Anecdotally seems to be more likely for relay to engage with speakers. When toggling from the OFF selection to speakers A just now, I just had the relay engage immediately upon switching modes so I find that unlikely to be a coincidence (of note it did start cycling in and out of protection though, ~10 seconds on/off). I'm also very certain the hiss is coming from either power amp ass'y 1 or 2. I'll take a closer look but the caps looked fine at a glance

 

[Anonky]

"Volume is turned up higher"

Does with or without speakers engaged make a difference?

Does the balance control (full left or full right) make a difference?

Can you see the tops of the small electrolytic caps.
I'm calling the end opposite of where the leads poke out the top - usually it has a line or groove in it so that if the cap wants to pop, those areas are weaker and will open up first at a lower pressure. Hisss not BLOOIE....

Regarding he hiss-- it occurs both with and without speakers engaged. Balance nor tone controls affect this component hiss. All of the caps on this board are light blue nichicons and do not have the perforations on top. I admittedly can't get a great up close look at them because i cant get the power amp assy 2 off the unit. I think the SP40 output packs are soldered into the board so I cant really move it.

 

[markthefixer]

Just a note: the two boards of the "power amplifier"

the board mounted vertically (parallel to the heat sink) has the power supply regulators and the protection circuits.
The board mounted horizontally between the heat sink and the first board is the actual amplifier board, it is connected to
two sp-40w power modules mounted on the big finned heat sink.

Regarding he hiss-- it occurs both with and without speakers engaged. Balance nor tone controls affect this component hiss.

Hmmm, unexpected....

But it still requires the volume to be turned up.

What about with the volume turned up, yet the unit is reading the empty aux inputs rather than the audio from the FM tuner.?

 

[Anonky]

Just a note: the two boards of the "power amplifier"

the board mounted vertically (parallel to the heat sink) has the power supply regulators and the protection circuits.
The board mounted horizontally between the heat sink and the first board is the actual amplifier board, it is connected to
two sp-40w power modules mounted on the big finned heat sink.


Hmmm, unexpected....

But it still requires the volume to be turned up.

What about with the volume turned up, yet the unit is reading the empty aux inputs rather than the audio from the FM tuner.?

Excellent question I had not yet considered. On AUX, no hiss!

Also, apologies-- you're correct. The board I was intending to refer to in the manual is "power amp assy 1." I cannot see any obvious bulging or deformities on these caps from the top view.

I agree I figured it would be a cap too. Referring back to the original post, I was told it had a blown "resistor fuse" by the seller. I don't see any obviously blown resistors on this board either; however several of the larger ones are covered in a white sleeve. Should I cut the sleeve open to get a better look?

 

[markthefixer]

no cutting.

Visually, if a sleeved resistor cut loose well enough to see it on a visual inspection, the sleeve would show damage or discoloration.

 

[markthefixer]

can you see cap tops on the horizontal amp board - the one with the relay?

 

[markthefixer]

Under a certain volume level of actual sound passing through the power amps the protect relay does NOT engage?
(aux is quiet, thus no engage).
Channel does not matter.

Or is the protect relay engagement independent of the sound level of the hissing.

independent of the protect, above a sound level through either channel, with or without speakers , hissing starts.

? where am I correct, where am I incorrect?

 

[Anonky]

can you see cap tops on the horizontal amp board - the one with the relay?

Yes. There are 6 electrolytic caps total. I’ve attached two images where you can see them from the top view. They are in the background of the photo focus but I’ve tried to get them in focus. Looks a bit dirty, I know. I just got this yesterday so don’t judge—I didn’t store this one, ha!

 

[Anonky]

Under a certain volume level of actual sound passing through the power amps the protect relay does NOT engage?
(aux is quiet, thus no engage).
Channel does not matter.

Or is the protect relay engagement independent of the sound level of the hissing.

independent of the protect, above a sound level through either channel, with or without speakers , hissing starts.

? where am I correct, where am I incorrect?

Relay will engage on any input. I believe I previous said relay was only engaging at high volume, but that’s no longer the case as today it has been engaging at low volumes too (very rarely will it engage upon power up like it is supposed to). But it doesn’t last for long once engaged. It goes into protection after less than 10 seconds generally and then cycle in and out.

Hiss is only on AM/FM inputs strangely. No hiss on phono or aux. I can’t directly relate the presence of hiss with the relay engaging. Hopefully that was clear—apologies for any previous inconsistencies

 

[Anonky]

Under a certain volume level of actual sound passing through the power amps the protect relay does NOT engage?
(aux is quiet, thus no engage).
Channel does not matter.

Or is the protect relay engagement independent of the sound level of the hissing.

independent of the protect, above a sound level through either channel, with or without speakers , hissing starts.

? where am I correct, where am I incorrect?

I can’t comment on whether the hiss is present when the relay engaged and speakers are making sound as it’s been happening pretty fast. I would have to assume it is making hiss. But hiss occurs regardless of +/- speakers on the specified inputs. The hiss though is only at high volumes (past 12oclock) and to be super clear the hiss is coming from the components in the unit itself—not the speakers.

 

[markthefixer]

we gotta check the power supply regulators.

dmm black lead to bare meal chassis ground

probe with INSULATED (all but a minute portion of the tip of the probe) red dmm lead:

from the bottom of the chassis:
pin 29 (s/b 33v)
pin 28 (s/b -34v)

From the top of the chassis:
pin 35 (s/b 13v)