blew up pioneer receiver

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Syprer

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Joined 2002
#1
I hope i'm at the right forym

My question:

I have a Pioneer SX-305RDS. One of my friends little kids has blew him up :-(

(the kid is 10year and I think it has misconnected the wires from the speakers so the the amplifier had a short circuit)

I think i need to replace the transistors, am I right?
So yes, do I need to do something else? (i was told something about a standby-power??, i don't know the english word)

since i now own it (he has given it to me) i want to repair it myself (as a newby🙂)
 
#3
seem very strange that the transistors is blow
a pioneer should have safety and fuses, so it not blow transistors
I know some of them uses IRFxxx IRF9xxx hex mosfet(IRF540/9540) for output
begin checking/changing fuses

if transistors are bad
see if anything around looks burned, black after a fire
 
#4
Syprer said:
(i was told something about a standby-power??, i don't know the english word)
Click to expand...

You have to check the transistors and replace the broken with similar onces. I don't know what you mean with 'standby-power'??? Do you mean the bias / quiescent current; in that case you don't have to adjust it if you use the same transistors.

HB.
 
#5
I can only find a fuse at the 230V entry, before the on/off button and the transfo.

For hugo: i mean "de ruststroom" like they say it in Dutch

It are TOSHIBA A1941 transistors
<url:http://www.semicon.toshiba.co.jp/en/bucat_11/bucat_1/bucat_1/td_15/TD.pdf>

between B and E: oneindig
B and C: oneindig
C and E: oneindig
C and B: 8Mohm
E and B: 8.5Mohm
E and C: oneindig
(oneindig = many many many megaohms, don't know the english word, kan onybody help me? symbol= oo)

is it broken?
 
#6
Syprer,

'ruststroom' = quiescent current (dutch: normaal gezien moet er niets aan deze instelling gewijzigd worden als gelijkaardige transistors worden gebruikt bij vervanging)

Do you have a diode test on your multimeter?? A transistor is build up of two diodes one between the base and the emitter, and one between the base and the collector. Diodes conduct just in one way, remember that with measuring ohms!!

'oneindig' = infinite.

check this thread on how to test transistors:
http://www.diyaudio.com/forums/showthread.php?threadid=7304

best regards,

HB.
 
#10
Eeeediot Proof ? - Not.

"seem very strange that the transistors is blow
a pioneer should have safety and fuses, so it not blow transistors"
Yeah right, sure thing. 🙄
If idiots did not blow up modern fragile amplifiers I wouldn't have a job to go to.
If you don't know, don't say ok.


Syprer, look for open circuit fusible resistors.
These may look ok but be O/C - you need to check with your DMM.
Put a 40W or 60W lamp across the mains fuseholder when first re-powering or use a variac after any repairs.

Eric.


"Better to keep your mouth shut than tell the world that you are a fool" - ?.
 
#12
Re: Eeeediot Proof ? - Not.

mrfeedback said:
Syprer, look for open circuit fusible resistors.
These may look ok but be O/C - you need to check with your DMM.
Put a 40W or 60W lamp across the mains fuseholder when first re-powering or use a variac after any repairs.
Click to expand...


There more than 300 resistors on the board, wish me luck ;-)
(is there a way to differ the fusible resistors from the 'normal' ones)
 
#15
I agree it is kind of cheap to put in mostly unworkable protection schemes. On the other hand I believe that if you make something indestructable then sell it to millions of people somebody will break it (thats where mrfeedback comes in). Also if their protection circuits worked all the time you would not have the amp. On a related note, my brother used to have one of those bookshelf systems, you could turn it very loud. On the bass hits the display would dim, and if you turned it up more a bass hit would occur and the display would go out, at which point the thing reset and turned off.

Good luck with your fix it job.
 
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