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.

 

[James Sweet]

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

The black grit is oxidation, it's common on older stuff and is in no way an
indication of failure. I would guess the transistors are fine, for that
matter how does the capacitor "look shot"? The only way you can tell it's
bad by looking at it is if it's so bad that it's bulging or leaking stinky
fish smelling electrolyte all over. Only way to test it is with an ESR
meter.

Chances are your crackling is nothing but a cracked solder joint or a dirty
switch, replacing the parts you mentioned are likely to have no effect other
than possibly requiring the bias to be readjusted.

 

[Bob Urz]

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.

Those old marantz were notorious for dirty tape monitor switches.


Bob

 

[Wild Bill]

I believe the RepairFAQ has detailed info regarding old home audio equipment
(as well as old equipment in general).

Two of the (many) common problems are switches and the brown glue. Scraping
away the glue and cleaning the location would usually take care of the
conductive path.
Treating the switches with DeoxIt usually cured any switch problems. Also do
the headphone jack contacts (another switch).

http://straylight.cso.niu.edu/repairfaq/REPAIR/F_Repair.html

Cheers
WB
................