Pioneer SX-950 wont come out of protection

[1MEGΩ]

It is a 2SC1318 NPN transistor.

You should be able to find it in Calgary. Wherever you go to buy one, someone there will be able to cross reference it. Look for a Industrial Electronics parts warehouse.

 

[1MEGΩ]

What ever you get, make sure it is not a NTE brand transistor.

https://alltransistors.com/transistor.php?transistor=53094

Here are the specs for a 2SC1318A transistor.

 

[CavScout]

What ever you get, make sure it is not a NTE brand transistor.

https://alltransistors.com/transistor.php?transistor=53094

Here are the specs for a 2SC1318A transistor.

The only local crossover part there is NTE 289A
Will this not work ?

 

[CavScout]

Will there be a problem with the NTE ?

 

[petehall347]

possibly but may well be ok for a regulator as it is being used for .

 

[CavScout]

Ok I will put it in there and see what happens

 

[CavScout]

Put in the NTE Transistor

Good news.......OUT OF PROTECTION AND PLAYING MUSIC ! YES !

Bad news.......lots of distortion. Sounds like a crappy $5 stereo, even at low volume.

Can this be the transistor?

 

[petehall347]

check the voltages again .

 

[petehall347]

if voltages ok we need to check the idle biases . and dc offsets

 

[CavScout]

Readings on Q5

Base 41.7v DC
Emitter -37.4v DC
Collector 36.9v DC

 

[petehall347]

you got those mixed up and marked one negative .
should be
collector 41.7v DC
base -37.4v DC
emitter 36.9v DC
looking good when it is correct way round ..

 

[CavScout]

Yes, sorry, no neg voltages.

So how do I check idle bias and DC offset ?

 

[petehall347]

now go to page 38 and study but ignore the 5.1k resistors as not needed . and do not touch the trimmers apart from vr1 and vr2 . set to 0v if possible .then just monitor the voltages for 10 minutes parts 8 9 and 10 .

 

[CavScout]

What do they mean by " set the power amplifier for NO LOAD" ?

28, 27,13 and 12
Have references to + and -
Does this mean the multimeter is hooked to both of those at once or are all these readings with the ground to frame?

 

[petehall347]

both and your meter can go either way if dmm type .. that was written for analogue meters as dmm.s not available back then .

 

[petehall347]

no load is no speakers .

 

[CavScout]

I made the adjustments and it sounded good for a few seconds but lots of distortion still

 

[CavScout]

Went back to make all of the adjustments. Everything was going well when vr4 was between 15 and 20mv I heard the protection relay click on and off a few times and now it won't come out of protection.
Also the Vr readings are:

Pins 9&10
-38.9v ( I had it very close to zero)
Pins 12&13
.113v ( I had it at 20mv)
Pins 24&25
.092v (I had it very close to zero)
Pins 27&28
.211v ( I had it at 20mv)

 

[CavScout]

Also getting a faint glow through the DBT

 

[Watthour]

It is reasonable to surmise that the power supply regulator transistor failed due to a fault and not from age. Excessive load is often the case. This can be from a faulty component downstream of the power supply, and that faulty component(s) can be creating the distortion you are hearing.

The faint glow of the DBT can be normal. If the power supply voltages are now within a normal range, the real troubleshooting can begin.