Replacing caps and transistors in an old Marantz 2240

[Beanie]

My old Marantz has had some crackling in the left channel for a while.
It's not heat related, since it was still there after I shelved the
unit for 3 months and plugged it in.

So I finally pulled the tone board out. One of the 25V caps looks
shot, so that's probably part of the culprit. It's marked as CE05 on
the board and the schematic (with CE06 matching it on the other
channel), and it's a 25V 4.7uF cap. I'll get a replacement for that
and fix it, and do CE06 at the same time. CE05-06 are the only 25V
caps on the board. From what I hear, the 25V caps are underrated,
and it would be adviseable for me to replace them with 35V caps. Easy
enough.

But as I was looking on the board, I noticed something peculiar about
transistors HE03, HE04, HE07, and HE08. All of them had some black
grit on the leads. It was easy to scrape off, but I assume that the
grit is an indicator of a shot transistor. Those transistors have a
note above the PE01 TONE AMP section on the schematic, stating:

HE03, E04, E07, E08
HT107632A (2SA763 4,5)

and the markings on the transistor read:

49
A673
WL5

I'm gonna go ahead and replace those while I have the unit apart.
Since
I'm pretty stupid when it comes to cross-referencing parts, could
someone point me in the right direction for a replacement for those
transistors? The datasheets for those transistors would be nice, too


Thanks,

--Chris

P. S. I'll try to get the schematic up on the web if it's wanted.

 

[Tim Schwartz]

Hello,

The black grit is probably silver oxide that has developed over time.
The transistors (2SA673) may well be fine. I find that rubbing alcohol
on a q-tip is good for removing this oxide, and be sure to clean the
bottom of the transistor where the leads come out, as it could be the
cause of the noise. Also, in general 25 volt caps are not a problem,
depending what they are being used for and what the power supply voltage
is, but it is unlikely to hurt to go to a 35V cap.

Regards,
Tim Schwartz
Bristol Electronics