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Marantz 2440 bad sound on right channel.

jFF_Bulbo

jFF_Bulbo

Active Member
Hello AKérs

I have a 2440 unit in restore proces. When it arrived it has poor sound on the right channel. So i decide to test the 2sc1445 transistors, two of them were in short. So i change one with. 2sc1445 and the other with nte175. The sound wasn´t equal an both channels, so i decide to change some parts.

When i read the mV according the manual, one channel tested and set to 20mV, (J714 & J718) wirth R730, but the other channel can bet fixed to 20mV, the read on J713 & J717 is about 550 mV no matter how i adjust R729..... i changed R729 with a 100k trimpot.... i can´t adjust the voltaje on that chanel, and this channel sound very poor...


I desolder and test H703. h707, H709 , H701 (2sc945) and no problems on them.... i changed the H705&H706 (both 2sc945) with modern 2SC945..... i also desoldered and tested C725 (0.1uf 200v), no problem.......

35v on power supply tested, it is OK

I changed capacitors: c407, c412, c401, c405, c410, (P400 tone and preamplifier board....)

wYeIE40.jpg




The last change i did was replace the 2sc945 transistors (h705&707)... and the soun was low and poor (i'll reinstall the previous 2sc945)...


No idea what to do on the next....
 
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jFF_Bulbo said:
I have a 2440 unit in restore proces. When it arrived it has poor sound on the right channel.
Click to expand...
Did you try cleaning the switches and controls before breaking out the multimeter?
 
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Don't use NTE parts, that could be your problem. Check your replacement pinouts and be sure you're using correct replacements.
 
ivandezande said:
Don't use NTE parts, that could be your problem. Check your replacement pinouts and be sure you're using correct replacements.
Click to expand...
Hello.
in fact, first i use original 2sc1445 (from a donor unit) and the problem persists. I saw the original 2sc1455 has a little lower hFE that the other 3, so i installed the nte175 wich had the most accurated hFE reading. will check it again.
 
I have a similar issue with a unit. I'm going to pull the output transistors and do a diode test on them.

Nte parts are junk if one works properly in a circuit consider yourself lucky.

Here are new originals
 
eizner23 said:
I have a similar issue with a unit. I'm going to pull the output transistors and do a diode test on them.

Nte parts are junk if one works properly in a circuit consider yourself lucky.
Click to expand...
I confess i am using a singe ESR tester to check the parts. So i alsa have a question, i found a electronic parts store wichs sells 2SC1445 transistor, but this are not TO-66 package, this are TO-220:
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KrD35Tk

Does anyone know abou it? i can´t find a datashhet od 2sc1445 who says it can be a TO-220 package.
Same case with 2SD315 transistor, originally to-66 but this store show it as a TO-220, no datasheet can be found.

Regards.
AlEKVJi
 
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Try this test with your multimeter.
See my edit for new originals if your in the US.
You'd jump thru many hoops to convert to66 to to220
 
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