"Jeffrey Landgraf" wrote in
:

Gentlemen,

My Yamaha P2100 stereo amplifier has "crackling" and hissing on a
single channel. It started out intermitant and would disapear (for
awhile) when the amp was turned off and then back on immediatley. The
audio from that channel is very thin sounding as well. I've replaced
all the electrolytic caps awhile back and the problem remains. I'm an
experienced board level trouble shooter but I'm trying to cut the time
for diagnosis to a minimum. In my experience "thin" is often dried out
caps but this amp design does not use many electrolytics ( and they've
been replaced!). I've not fixed an amp with crackling and hissing.
Any ideas on which components would likely cause these symptoms?

Thanks,
Jeff


You need to trace the noise back from the output with an oscilloscope.
This can be tedious without a schematic. Go back stage by stage. Does the
power amp have discrete transistors or a big hybrid block? Email me if
you like.

Tim

In article ,
"Jeffrey Landgraf" wrote:

Gentlemen,

My Yamaha P2100 stereo amplifier has "crackling" and hissing on a single
channel. It started out intermitant and would disapear (for awhile) when
the amp was turned off and then back on immediatley. The audio from that
channel is very thin sounding as well. I've replaced all the electrolytic
caps awhile back and the problem remains. I'm an experienced board level
trouble shooter but I'm trying to cut the time for diagnosis to a minimum.
In my experience "thin" is often dried out caps but this amp design does not
use many electrolytics ( and they've been replaced!). I've not fixed an amp
with crackling and hissing. Any ideas on which components would likely
cause these symptoms?

Thanks,
Jeff



It sounds like a bad solder connection, corroded switch, moisure in the
circuit board, hydrated flux, or a leaky semiconductor. Try tapping,
heat, and cold to modulate the hiss.

My old Realistic STA-720 just started doing this. The frequency counter
goes all nuts and flickers along with the noise. My bet is that it's
regulator transistor has unsoldered itself again. I have to see if I
can fit a bigger heatsink on it.

Tim,

It's on the bench with a dummy load and scoping it was my plan. I do have
the schematic and yes it can be tedious work. That's why I thought you guys
might be able to direct me to a particular part type failure that would be
characteristic of this kind of noise. It is discrete transistor.

Thanks for the advice,
Jeff


"Browntimdc" wrote in message
...
"Jeffrey Landgraf" wrote in
:

Gentlemen,

My Yamaha P2100 stereo amplifier has "crackling" and hissing on a
single channel. It started out intermitant and would disapear (for
awhile) when the amp was turned off and then back on immediatley. The
audio from that channel is very thin sounding as well. I've replaced
all the electrolytic caps awhile back and the problem remains. I'm an
experienced board level trouble shooter but I'm trying to cut the time
for diagnosis to a minimum. In my experience "thin" is often dried out
caps but this amp design does not use many electrolytics ( and they've
been replaced!). I've not fixed an amp with crackling and hissing.
Any ideas on which components would likely cause these symptoms?

Thanks,
Jeff


You need to trace the noise back from the output with an oscilloscope.
This can be tedious without a schematic. Go back stage by stage. Does the
power amp have discrete transistors or a big hybrid block? Email me if
you like.

Tim

Kevin,

I had thought about doing a quick resolder since I also suspected this could
the case. Don't think moisture is problem since it's rather dry here.
Shooting some freeze on things should put me in the ball park if it's a
leaky transistor.

Thanks,
Jeff


"Kevin McMurtrie" wrote in message
...
In article ,
"Jeffrey Landgraf" wrote:

Gentlemen,

My Yamaha P2100 stereo amplifier has "crackling" and hissing on a single
channel. It started out intermitant and would disapear (for awhile) when
the amp was turned off and then back on immediatley. The audio from that
channel is very thin sounding as well. I've replaced all the
electrolytic
caps awhile back and the problem remains. I'm an experienced board level
trouble shooter but I'm trying to cut the time for diagnosis to a
minimum.
In my experience "thin" is often dried out caps but this amp design does
not
use many electrolytics ( and they've been replaced!). I've not fixed an
amp
with crackling and hissing. Any ideas on which components would likely
cause these symptoms?

Thanks,
Jeff



It sounds like a bad solder connection, corroded switch, moisure in the
circuit board, hydrated flux, or a leaky semiconductor. Try tapping,
heat, and cold to modulate the hiss.

My old Realistic STA-720 just started doing this. The frequency counter
goes all nuts and flickers along with the noise. My bet is that it's
regulator transistor has unsoldered itself again. I have to see if I
can fit a bigger heatsink on it.

In , on 08/05/03
at 04:48 PM, "Jeffrey Landgraf" said:

Gentlemen,

My Yamaha P2100 stereo amplifier has "crackling" and hissing on a
single channel. It started out intermitant and would disapear (for
awhile) when the amp was turned off and then back on immediatley. The
audio from that channel is very thin sounding as well. I've replaced
all the electrolytic caps awhile back and the problem remains. I'm an
experienced board level trouble shooter but I'm trying to cut the time
for diagnosis to a minimum. In my experience "thin" is often dried out
caps but this amp design does not use many electrolytics ( and they've
been replaced!). I've not fixed an amp with crackling and hissing.
Any ideas on which components would likely cause these symptoms?

10 to 15 minutes of *VERY* careful visual inspection is often more
useful than several hours of diagnostic probing.

"Thin" sounding is usually a feedback problem at the input
differential. (Yes, it could be a coupling capacitor, but modern amps
don't use many. Be sure to check the input capacitor and any emitter
bypass capacitors.) Look for tantalum capacitors. I trust them as much
or less than electrolytics. For some reason the blue 1uF tantalums love
to short.

Is the gain nearly identical in the two channels?

Flex the chassis and the boards. If the amp fusses while you flex, give
it a closer visual inspection and refine your flexes.

Use cold or hot to stress the amp. At first be gross about it, flood
the whole thing with hot or cold and see if there is a response, then
refine your search.

-----------------------------------------------------------
SPAM:
wordgame:123(abc):14 9 20 5 2 9 18 4 at 22 15 9 3 5 14 5 20 dot 3 15
13 (Barry Mann)
[sorry about the puzzle, SPAMers are ruining my mailbox]
-----------------------------------------------------------

Don't forget dirty relays.



Gareth.


"Jeffrey Landgraf" wrote in message
...
Gentlemen,

My Yamaha P2100 stereo amplifier has "crackling" and hissing on a single
channel. It started out intermitant and would disapear (for awhile) when
the amp was turned off and then back on immediatley. The audio from that
channel is very thin sounding as well. I've replaced all the electrolytic
caps awhile back and the problem remains. I'm an experienced board level
trouble shooter but I'm trying to cut the time for diagnosis to a minimum.
In my experience "thin" is often dried out caps but this amp design does
not
use many electrolytics ( and they've been replaced!). I've not fixed an
amp
with crackling and hissing. Any ideas on which components would likely
cause these symptoms?

Thanks,
Jeff

In my experience, freezer works only very occasionally.
Resoldering every joint is often far more effective and really won't take
anything near as long as you think it would, and if it doesn't work at least
you know it's not a dry joint.





I had thought about doing a quick resolder since I also suspected this
could
the case. Don't think moisture is problem since it's rather dry here.
Shooting some freeze on things should put me in the ball park if it's a
leaky transistor.

"M. Smith" smithm@networkusadotnet wrote in
:

"Browntimdc" wrote in message
...
"Jeffrey Landgraf" wrote in
:

Gentlemen,

My Yamaha P2100 stereo amplifier has "crackling" and hissing on a
single channel. It started out intermitant and would disapear (for
awhile) when the amp was turned off and then back on immediatley. The
audio from that channel is very thin sounding as well. I've replaced
all the electrolytic caps awhile back and the problem remains. I'm an
experienced board level trouble shooter but I'm trying to cut the time
for diagnosis to a minimum. In my experience "thin" is often dried out
caps but this amp design does not use many electrolytics ( and they've
been replaced!). I've not fixed an amp with crackling and hissing.
Any ideas on which components would likely cause these symptoms?

Thanks,
Jeff


My first inclination would be to look for a bad solder joint. I've had them
cause audio problems of the nature you're referring to.




Try using temperature as an aid in your troubleshooting endeavors. Place the
unit in your refrigerator overnight and see if the problem diminishes or
disappears while it is cold.

r


--
"Any sufficiently advanced technology is indistinguishable from
magic."

Arthur C. Clarke (1917 - ), "Technology and the Future"

Jeffrey Landgraf:
Be certain to look at the good responses and repair
suggestions you are obtaining with your DUPLICATE
posting on the newsgroup sci.electronics.repair .
As I stated to you there in a reply post I think you
should be concentrating on looking for cracked, cold,
or otherwise faulty solder connections on the main
circuit board, especially near and around the high
heat producing parts such as power semiconductors,
diodes, resistors, etc. Re-solder as needed.
Very IMPORTANT..... you would be best advised to STOP
using your amp until you get this fixed, either by you
or by a service shop. If you continue to try to use
the amp with this problem you risk additional and
major (read EXPENSIVE $$$) failures.
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -


snipped:
"Jeffrey Landgraf" wrote in message

with crackling and hissing. Any ideas on which components would likely
cause these symptoms?

It's on the bench with a dummy load and scoping it was my plan. I do have
the schematic and yes it can be tedious work. That's why I thought you guys
might be able to direct me to a particular part type failure that would be
characteristic of this kind of noise. It is discrete transistor.

My Yamaha P2100 stereo amplifier has "crackling" and hissing on a
single channel. It started out intermitant and would disapear (for

I've not fixed an amp with crackling and hissing.
Any ideas on which components would likely cause these symptoms?

Thanks to all for the suggestions. I checked the main board last night and
found that I had resoldered the entire "bad" channel the first time I had
worked on it. This problem has been driving me crazy. I have it on the
bench with a dummy load and scope, but the noises didn't show on the scope!
I may have to reconnect to speakes to see if the problem is now in
"remission". But, connection to expensive JBL studio series speakers is
riskey! The noises are low level, but should show on the o-scope. Both
channels looked identical. I have some inexpensive headphones so I may try
connecting my headphone distribution box instead. I also stressed the
board to see if it would return but the output signals looked clean. There
are subboards where the output transistors connect but to resolder I'll have
to de-solder the output transistors, remove the board and flip it to get
access to the solder side (what a pain).

Jeff Landgraf


"Gareth Magennis" wrote in message
. ..
Don't forget dirty relays.



Gareth.


"Jeffrey Landgraf" wrote in message
...
Gentlemen,

My Yamaha P2100 stereo amplifier has "crackling" and hissing on a single
channel. It started out intermitant and would disapear (for awhile)
when
the amp was turned off and then back on immediatley. The audio from
that
channel is very thin sounding as well. I've replaced all the
electrolytic
caps awhile back and the problem remains. I'm an experienced board
level
trouble shooter but I'm trying to cut the time for diagnosis to a
minimum.
In my experience "thin" is often dried out caps but this amp design does
not
use many electrolytics ( and they've been replaced!). I've not fixed an
amp
with crackling and hissing. Any ideas on which components would likely
cause these symptoms?

Thanks,
Jeff