Problem with my SX 780

rediffusion

New Member
Hi,

This is my first post here. I bought a Pioneer SX 780 receiver back in 2013 and it’s been working well until recently. Over the last few weeks when I turn it on everything lights up but I can’t get any sound out of it - radio, turntable , aux plus I can't get any sound from the headphones. There’s obviously power going to it but for some reason there’s no sound. The speaker cables are all connected correctly. When I used to turn it on, the lights came on then after a second or two there would be a click and the audio would play. This doesn’t happen anymore.

I asked this question at stevehoffman.tv and was directed to this forum.

Does anybody know what the problem could be? It has been suggested that it might be a delay/protection relay problem.

Strangely, a week or two after this started happening I had to turn the power off in my house for 20 minutes. When I turned it back on the stereo started playing as normal. It worked for the rest of the day but when I turned it on the next day – nothing.

I live in Fairfield, CT and was wondering if anybody could recommend a place to get this serviced that's not too far away from me.

Thanks for taking the time to read. Any advice would be gratefully received.

R ;)

2017_02_12_14_33_52.jpg
 
Hi,

This is my first post here. I bought a Pioneer SX 780 receiver back in 2013 and it’s been working well until recently. Over the last few weeks when I turn it on everything lights up but I can’t get any sound out of it - radio, turntable , aux plus I can't get any sound from the headphones. There’s obviously power going to it but for some reason there’s no sound. The speaker cables are all connected correctly. When I used to turn it on, the lights came on then after a second or two there would be a click and the audio would play. This doesn’t happen anymore.

I asked this question at stevehoffman.tv and was directed to this forum.

Does anybody know what the problem could be? It has been suggested that it might be a delay/protection relay problem.

Strangely, a week or two after this started happening I had to turn the power off in my house for 20 minutes. When I turned it back on the stereo started playing as normal. It worked for the rest of the day but when I turned it on the next day – nothing.

I live in Fairfield, CT and was wondering if anybody could recommend a place to get this serviced that's not too far away from me.

Thanks for taking the time to read. Any advice would be gratefully received.

R ;)

Maybe, or an amplifier issue causing it to go into protection. However some things I would want to check for are bad solder joints and power supply issues.
 
Thanks for the reply, Glen.

I'm not really technically minded when it comes to electronics. What's the best way to find a reputable person/company to take a look at it? Any tips?
 
I'd post your location in your profile if you want someone else to have a look, and I bet you'll have some AKers nearby who could help. Or someone can direct you to someone local to you.
 
I hope it's OK to bump this thread. Can anybody recommend a reputable person/company to take a look at my SX760 within a reasonable distance from Fairfield, CT? Failing that, what's the best way to find somebody that will do a decent job?

Many thanks in advance.
 
Bumping thread. Same Problem, everything lights up, tuner vu also working. No sound and no clicking.

As another post suggested, I checked Darlington packs on 200v dc with the following results

Left Pac Right Pac

1 +19 1 -40.4
2 -41.3 2 -41.5
3 -41.3 3 -39.2
8 + 41.6 8 -39.3
9 +41.4 9 +41.4
10 +21.8 10 -39.5

Also checked .22 ohm resistors at pins 3-5 and 6-8 and one is bad on left.

Should I order a like resistor .22 ohm not sure about watts is 5 o.k.?

Thank you for any help!
 
Did you remove one leg and test the resistor(s)?
You are on the right track.
.22 ohm 5 watt. Replace all four.
Get the resistors sorted and perform the DC Balance check.
It might just come around.

The right channel is good.
 
Did you remove one leg and test the resistor(s)?
You are on the right track.
.22 ohm 5 watt. Replace all four.
Get the resistors sorted and perform the DC Balance check.
It might just come around.

The right channel is good.

Thank you for the help.

I did not remove a leg of the resistors, just an ohms meter across the two legs and one resistor is infinite or "ol " on my meter which I guess it means it is open.

Guess I will order the resistors off eBay
 
Last edited:
I have a ton of these:
Mouser:
588-TUW5JR20E, 0.20 OHM 5 WATT Wirewround. Through Hole.
They should work fine.
I can send four if you wish.
PM me if interested.

DSC03912.JPG
 
The output thick film IC associated with the open emitter resistor is gone. Replacement is cheap and easy if you get a genuine part.
Don't think any of it will last without a restoration. After 40-years, it won't last.
 
The output thick film IC associated with the open emitter resistor is gone. Replacement is cheap and easy if you get a genuine part.
Don't think any of it will last without a restoration. After 40-years, it won't last.


Help me understand, is there a certain IC thats needs replacement also?
 
The voltages are almost there, minus the open emitter resistor on one side. I think the modules are fine. Once the resistor(s) is replaced we can see if it will operate with the correct voltages.
If the module voltages are not behaving then a module is needed. Either way the resistor(s) have to be replaced. No harm done.
Like I said I think the set will respond favorably.
 
The voltages are almost there, minus the open emitter resistor on one side. I think the modules are fine. Once the resistor(s) is replaced we can see if it will operate with the correct voltages.
If the module voltages are not behaving then a module is needed. Either way the resistor(s) have to be replaced. No harm done.
Like I said I think the set will respond favorably.
 
Readings before( left column) and after( right column) i replaced resistors, hopefully, correctly!

L R
1 +19 +18 1 -40.4 -.01
2 -41.3 -41 2 -41.5 -41
3 -41.3 -41 3 -39.2 -0
8 +41.6 -41 8 -39.3 -0
9 +41.4 +41 9 +41.4 +41
10 +21.8 +21 10 -39.5 + 01
 
L Power pack
Before
Pin 1 + 19 After 1 +18
2 -41.3 2 -41
3 -41.3 3-41
8 + 41.6 8 -41
9 +41.4 9 +41
10 + 21.8 10 +21

Right Power Pack
1 -40.4 1-.01
2 -41.5 2 -41
3 -39.2 3 0
8 -39.3 8 0
9 + 41.4 9 +41
10 -39.5 10 +01
 
I really messed this up. I don't what I was looking at but the packs are toast.
The voltages at pins 3 and 8 should be very near zero (0v's).
Both packs shorted is uncommon but they are.
Your first readings showed it.

Sorry I missed that.

The readings show like the pack is not even there or soldered in. The left pack has a slight voltage change.
I have one good pack here if you want it I'll send it. You'll have to scrounge for another one.
 
I really messed this up. I don't what I was looking at but the packs are toast.
The voltages at pins 3 and 8 should be very near zero (0v's).
Both packs shorted is uncommon but they are.
Your first readings showed it.

Sorry I missed that.

The readings show like the pack is not even there or soldered in. The left pack has a slight voltage change.
I have one good pack here if you want it I'll send it. You'll have to scrounge for another one.


I was suspecting the packs, I got a couple off eBay, for an SX-1000 that are the same numbers, that I can use.
 
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