Pioneer Receiver SX-408

[audioPT]

Hi!

One more time, I'm here to get some help.

A friend of mine put in the trash this:
:ioneer Stereo Receiver SX-408::

I bring it to my workshop and found that it is 'dead' .

So, any1 have a schematic for this?
I know it is very old, but you know the sound of that kind of equipment.
I must bring it to live!

Thanka in advance for some reply.

Pedro Martins

 

[audioPT]

Pioneer Stereo Receiver SX-408



Schematic, please!!

Thanks

Pedro Martins

 

[mrfeedback]

A Picture Is Worth A Thousand Words...

Can you post photo of outside and inside ?.
If so I can probably help you.

Eric.

 

[316a]

Dead ?

Check fuses , if the fuses are ok it may be the thermal trip on the transformer . If the thermal trip has gone open you could always short it to check operation but this may not be a safe method (I use a variac to bring the mains up slowly) , or if it's an inline type bonded to the transformer just buy a new one (sometimes they are impossible to replace) . Usually the trips go when the the ventilation holes on the top have been blocked , usually accompanied with the bass at full and loudness button depressed on the amp !

316a

 

[audioPT]

Hi!

Thanks for the replyes.

I've cheched some components and I found this:
- Fuses OK
- PSU working fine
- One 150 Ohm resistor going very hot!
- Lift up one side of the resistor and...
- Doesn't get hot anymore

This resistor connects with a 2SA720 that is shorted.
Please, let me know, as this is the cause of the problem, and as I can't get that 2SA here in portugal, can I use a BC640 in it's place?

They are pin compatible and the specs are:

2SA720
30V | 0,5A | 0,625W
BC640
100V | 1A | 0,8W


Photo:
Don't have a digital camera but I'm going to try my webcam.

All I know is that it is Beautifull!
Aluminium in front and the rest of the case black. Also have a tunning pointer with a light on it.

Thanks mrfeedback and 316a for the replyes.

Are these transistors compatible??

Best regards

Pedro Martins

 

[Netlist]

Yes, the transistors can be exchanged. Expect for the lower bandwith. 200 vs 50Mhz. But that's not too important IMO.

/Hugo

 

[Tube_Dude]

Olá audioPT

You can also use the BC327!

-50 V-0,8 Amps-100 Mhz-0,625 W

It is very comum here in Portugal ,but if you don't find one send me a mail because a have some !

Saudações

Jorge Santos

 

[mrfeedback]

Be sure to check/adjust bias current after replacing the drivers.
If the repaired channel works fine (it should), you should do the same to the other channel to conserve stereo matching.

Eric.

 

[audioPT]

Bias! Of course. The amplifier don't have any adjustements.
I've compared the good one with the repaired and the current was the same. Also substituted the 2SA720 with BC640 in both channels.
Wanna know if it works?
Yes!
And with the known sound of that kind of amplifiers...

Guys, Thanks for all the replyes!

Best regards,

Pedro Martins

 

[survey]

I have the schematic you want, but its to big to upload.

I can´t mail you either, I'm new here and my account is under moderation...

mail me
cheer's.

 

[panoramamonk]

Pioneer Receiver SX408

Hi,

I have a unit which works except the AM. Sometime ago it started to make "poping" sound with the broadcast and now it is just noise heard and no signal as indicated. When I touched the area around the VC some broadcast can be barely heard for a second or two then "poping" again. May I know where it goes wrong plus diagrams? This is a very old unit, but matches the size and face of a cassette for my wife's use.

My email: panorammonk@gmail.com

Thanking you in advance!