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Old 1st March 2003, 07:22 PM   #1
audioPT is offline audioPT  Portugal
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Unhappy Pioneer Receiver SX-408



Hi!

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

A friend of mine put in the trash this:
::Pioneer 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
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Old 4th March 2003, 10:27 AM   #2
audioPT is offline audioPT  Portugal
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Default Pioneer Stereo Receiver SX-408



Schematic, please!!

Thanks

Pedro Martins
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Old 4th March 2003, 11:06 AM   #3
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Default A Picture Is Worth A Thousand Words...

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

Eric.
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Old 4th March 2003, 11:45 AM   #4
316a is offline 316a  England
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Default 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
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Old 4th March 2003, 11:58 AM   #5
audioPT is offline audioPT  Portugal
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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
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Old 4th March 2003, 12:32 PM   #6
Netlist is offline Netlist  Belgium
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Yes, the transistors can be exchanged. Expect for the lower bandwith. 200 vs 50Mhz. But that's not too important IMO.

/Hugo
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Old 4th March 2003, 06:11 PM   #7
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Default 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
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Old 5th March 2003, 12:44 AM   #8
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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.
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Old 5th March 2003, 05:58 PM   #9
audioPT is offline audioPT  Portugal
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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
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Old 21st April 2009, 01:59 PM   #10
survey is offline survey  Portugal
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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.
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