LANEY B1 (Tripath) audio Amp - Blown outputs

C

Circuit

Guest
I am repairing this amp which is using the Tripath TA0104 preamp chip. The
output transistors are STW38NB20's (W38NB20) . I have found a supplier with
the transistors in stock. At least one is shorted from what looks like a
liquid spill near the heatsink where they mount onto.

When powered up, and input signal applied, I can see the LED-VU levels
bounce on both the input and output monitoring. There is a green LED near
the tripath chip which is not lit, labeled 'run'. Does this mean the Tripath
chip is not running and ought to be replaced? I have read about some
replacements for this chip which are inconclusive. Ought I just replace it,
or is the run light a sign its bad? Nothing else seems burnt, but there are
2 black color hi-watt resistors that dont seem to have any resistance at
all, and may be open, but I need to remove them from the board to be sure.
They are shown in the photo below each channels power transistors. No
schematics - Thanks for any input.

Image of amp's mainboard:
www.imagechicken.com/uploads/1241464995039779400.jpg
 
Circuit <nospam@webform.org> wrote in message
news:gtnbls$paj$1@adenine.netfront.net...
I am repairing this amp which is using the Tripath TA0104 preamp chip. The
output transistors are STW38NB20's (W38NB20) . I have found a supplier
with
the transistors in stock. At least one is shorted from what looks like a
liquid spill near the heatsink where they mount onto.

When powered up, and input signal applied, I can see the LED-VU levels
bounce on both the input and output monitoring. There is a green LED near
the tripath chip which is not lit, labeled 'run'. Does this mean the
Tripath
chip is not running and ought to be replaced? I have read about some
replacements for this chip which are inconclusive. Ought I just replace
it,
or is the run light a sign its bad? Nothing else seems burnt, but there
are
2 black color hi-watt resistors that dont seem to have any resistance at
all, and may be open, but I need to remove them from the board to be sure.
They are shown in the photo below each channels power transistors. No
schematics - Thanks for any input.

Image of amp's mainboard:
www.imagechicken.com/uploads/1241464995039779400.jpg
Click to expand...

What are the 2 symetrically placed angular black lumps ? more epoxied hybrid
specials ?


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/
 
N_Cook <diverse@tcp.co.uk> wrote in message
news:gtnd82$t01$1@news.motzarella.org...
Circuit <nospam@webform.org> wrote in message
news:gtnbls$paj$1@adenine.netfront.net...
I am repairing this amp which is using the Tripath TA0104 preamp chip.
The
output transistors are STW38NB20's (W38NB20) . I have found a supplier
with
the transistors in stock. At least one is shorted from what looks like a
liquid spill near the heatsink where they mount onto.

When powered up, and input signal applied, I can see the LED-VU levels
bounce on both the input and output monitoring. There is a green LED
near
the tripath chip which is not lit, labeled 'run'. Does this mean the
Tripath
chip is not running and ought to be replaced? I have read about some
replacements for this chip which are inconclusive. Ought I just replace
it,
or is the run light a sign its bad? Nothing else seems burnt, but there
are
2 black color hi-watt resistors that dont seem to have any resistance at
all, and may be open, but I need to remove them from the board to be
sure.
They are shown in the photo below each channels power transistors. No
schematics - Thanks for any input.

Image of amp's mainboard:
www.imagechicken.com/uploads/1241464995039779400.jpg



What are the 2 symetrically placed angular black lumps ? more epoxied
hybrid
specials ?


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/
Click to expand...

Second viewing they are high current automotive type relays. The first thing
to do is remove the obviously bad and then power up on much reduced voltage
and check the prea is ok, if stable, and nothing else shows up as bad


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/
 
What is the year decade digit under the cable tie, ends 049 ?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/
 
"Circuit" <nospam@webform.org> wrote in message
news:gtnbls$paj$1@adenine.netfront.net...
I am repairing this amp which is using the Tripath TA0104 preamp chip. The
output transistors are STW38NB20's (W38NB20) . I have found a supplier with
the transistors in stock. At least one is shorted from what looks like a
liquid spill near the heatsink where they mount onto.

When powered up, and input signal applied, I can see the LED-VU levels
bounce on both the input and output monitoring. There is a green LED near
the tripath chip which is not lit, labeled 'run'. Does this mean the
Tripath chip is not running and ought to be replaced? I have read about
some replacements for this chip which are inconclusive. Ought I just
replace it, or is the run light a sign its bad? Nothing else seems burnt,
but there are 2 black color hi-watt resistors that dont seem to have any
resistance at all, and may be open, but I need to remove them from the
board to be sure. They are shown in the photo below each channels power
transistors. No schematics - Thanks for any input.

Image of amp's mainboard:
www.imagechicken.com/uploads/1241464995039779400.jpg
Click to expand...
Download a copy of the service manual for the B1 from
http://tremolo.elektroda.net/Firmowe/LANEY/B1-2-3%20Series.pdf. Then,
download a copy of the datasheet for the TA0104 driver from
http://www.datasheet4u.com/ and look at the signals. The Run LED gets turned
on by the HMute output of the TA0104. If the Run LED is off, then the audio
is muted (off).

Since the TA0104 is DC coupled to the output FETs, then it's a good bet that
it has been destroyed. If the black "hi-watt resistors" that you're
talking about are the large devices on either side of the TA0104, then
they're probably the protection relays, not resistors. You'll have to remove
them from the board and energize them with a power supply in order to verify
them.

In searching for the schematic, I found a few forum posts that indicated
that parts for the B1 and its siblings are nearly impossible to find.
Hope this gets you started.

Cheers!

--
Dave M
masondg44 at comcast dot net

One good thing about Alzheimer's; you get to meet new people every day.
 
Yes. Those resistors I forgot to mark them in the picture but they are below
the ceramic resistors and above the relays you pointed out - they check ok
at 1K each. I have replaced the transistors hoping this is all it needs.
Hopefully the tripath IC is ok and needs no replacing. Will power upo later
and post an update.

Second viewing they are high current automotive type relays. The first
thing
to do is remove the obviously bad and then power up on much reduced
voltage
and check the prea is ok, if stable, and nothing else shows up as bad
Click to expand...
 
Circuit wrote:

I am repairing this amp which is using the Tripath TA0104 preamp chip. The
output transistors are STW38NB20's (W38NB20) . I have found a supplier with
the transistors in stock. At least one is shorted from what looks like a
liquid spill near the heatsink where they mount onto.

When powered up, and input signal applied, I can see the LED-VU levels
bounce on both the input and output monitoring. There is a green LED near
the tripath chip which is not lit, labeled 'run'. Does this mean the Tripath
chip is not running and ought to be replaced?
Click to expand...
Do they still have a website ? Get the app note.

I suggest you replace blown devices before drawing any conclisions.

Graham
 
N_Cook wrote:

Second viewing they are high current automotive type relays.
Click to expand...
No, they're not automotive, they're good for mains AC. I should know, I've used
them.

N_Cook is wrong as ever.

What are you going to 'bodge' today btw ?

Graham
 
Dave M <masondg4499@comcast.net> wrote in message
news:tbydnZXmo5LComLUnZ2dnUVZ_j2dnZ2d@giganews.com...
"Circuit" <nospam@webform.org> wrote in message
news:gtnbls$paj$1@adenine.netfront.net...
I am repairing this amp which is using the Tripath TA0104 preamp chip.
The
output transistors are STW38NB20's (W38NB20) . I have found a supplier
with
the transistors in stock. At least one is shorted from what looks like a
liquid spill near the heatsink where they mount onto.

When powered up, and input signal applied, I can see the LED-VU levels
bounce on both the input and output monitoring. There is a green LED
near
the tripath chip which is not lit, labeled 'run'. Does this mean the
Tripath chip is not running and ought to be replaced? I have read about
some replacements for this chip which are inconclusive. Ought I just
replace it, or is the run light a sign its bad? Nothing else seems
burnt,
but there are 2 black color hi-watt resistors that dont seem to have any
resistance at all, and may be open, but I need to remove them from the
board to be sure. They are shown in the photo below each channels power
transistors. No schematics - Thanks for any input.

Image of amp's mainboard:
www.imagechicken.com/uploads/1241464995039779400.jpg


Download a copy of the service manual for the B1 from
http://tremolo.elektroda.net/Firmowe/LANEY/B1-2-3%20Series.pdf. Then,
download a copy of the datasheet for the TA0104 driver from
http://www.datasheet4u.com/ and look at the signals. The Run LED gets
turned
on by the HMute output of the TA0104. If the Run LED is off, then the
audio
is muted (off).

Since the TA0104 is DC coupled to the output FETs, then it's a good bet
that
it has been destroyed. If the black "hi-watt resistors" that you're
talking about are the large devices on either side of the TA0104, then
they're probably the protection relays, not resistors. You'll have to
remove
them from the board and energize them with a power supply in order to
verify
them.

In searching for the schematic, I found a few forum posts that indicated
that parts for the B1 and its siblings are nearly impossible to find.
Hope this gets you started.

Cheers!

--
Dave M
masondg44 at comcast dot net

One good thing about Alzheimer's; you get to meet new people every day.
Click to expand...

Yes, before spending out on power transistors its necessary to establish
that that big lump proprietary is still functional.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/
 
"Circuit" <nospam@webform.org> wrote in message
news:gtnbls$paj$1@adenine.netfront.net...
I am repairing this amp which is using the Tripath TA0104 preamp chip. The
output transistors are STW38NB20's (W38NB20) . I have found a supplier with
the transistors in stock. At least one is shorted from what looks like a
liquid spill near the heatsink where they mount onto.

When powered up, and input signal applied, I can see the LED-VU levels
bounce on both the input and output monitoring. There is a green LED near
the tripath chip which is not lit, labeled 'run'. Does this mean the
Tripath chip is not running and ought to be replaced? I have read about
some replacements for this chip which are inconclusive. Ought I just
replace it, or is the run light a sign its bad? Nothing else seems burnt,
but there are 2 black color hi-watt resistors that dont seem to have any
resistance at all, and may be open, but I need to remove them from the
board to be sure. They are shown in the photo below each channels power
transistors. No schematics - Thanks for any input.

Image of amp's mainboard:
www.imagechicken.com/uploads/1241464995039779400.jpg
Click to expand...
Without getting into a drawn-out pissing contest about the definition of a
'digital' amplifier, be aware that Tripath devices are not analogue in the
conventional sense that you might be used to working with on high power band
equipment. They are a form of switch-mode or PWM driver or amplifier, which
they as a company define as "digital". From my experiences with them, they
are difficult to apply 'conventional' fault-finding techniques to, and are
notoriously fickle on whether they decide to work or not, whether they
decide to fail or not when the output switching FETs on the end of them go
short, and whether or not they decide to re-twat the output FETs after
you've replaced them (either immediately, or after just long enough a period
to make you think you've fixed the thing ... !! )

You might be lucky. Sometimes it all works out just as you hope and expect,
but other times it doesn't. I'll wish you good luck, 'coz you might just
need it ... :-\

Arfa
 
Arfa Daily <arfa.daily@ntlworld.com> wrote in message
news:2l_Ll.22578$A85.17504@newsfe03.ams2...
"Circuit" <nospam@webform.org> wrote in message
news:gtnbls$paj$1@adenine.netfront.net...
I am repairing this amp which is using the Tripath TA0104 preamp chip.
The
output transistors are STW38NB20's (W38NB20) . I have found a supplier
with
the transistors in stock. At least one is shorted from what looks like a
liquid spill near the heatsink where they mount onto.

When powered up, and input signal applied, I can see the LED-VU levels
bounce on both the input and output monitoring. There is a green LED
near
the tripath chip which is not lit, labeled 'run'. Does this mean the
Tripath chip is not running and ought to be replaced? I have read about
some replacements for this chip which are inconclusive. Ought I just
replace it, or is the run light a sign its bad? Nothing else seems
burnt,
but there are 2 black color hi-watt resistors that dont seem to have any
resistance at all, and may be open, but I need to remove them from the
board to be sure. They are shown in the photo below each channels power
transistors. No schematics - Thanks for any input.

Image of amp's mainboard:
www.imagechicken.com/uploads/1241464995039779400.jpg


Without getting into a drawn-out pissing contest about the definition of a
'digital' amplifier, be aware that Tripath devices are not analogue in the
conventional sense that you might be used to working with on high power
band
equipment. They are a form of switch-mode or PWM driver or amplifier,
which
they as a company define as "digital". From my experiences with them, they
are difficult to apply 'conventional' fault-finding techniques to, and are
notoriously fickle on whether they decide to work or not, whether they
decide to fail or not when the output switching FETs on the end of them go
short, and whether or not they decide to re-twat the output FETs after
you've replaced them (either immediately, or after just long enough a
period
to make you think you've fixed the thing ... !! )

You might be lucky. Sometimes it all works out just as you hope and
expect,
but other times it doesn't. I'll wish you good luck, 'coz you might just
need it ... :-\

Arfa
Click to expand...

So are we talking about a class D driver stage , rather than preamp in the
black lump ? I've only looked at the OP's pic


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/
 
N_Cook wrote:

So are we talking about a class D driver stage , rather than preamp in the
black lump ?
Click to expand...
YES.

Although Tripath called it 'class T' since it doesn't have a fixed switching
frequency.

I doubt you'll see this since you seem to ignore me despite the fact I know this
stuff.

Graham
 
"Eeyore" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:4A018DEC.F035C38D@hotmail.com...
N_Cook wrote:

So are we talking about a class D driver stage , rather than preamp in
the
black lump ?

YES.

Although Tripath called it 'class T' since it doesn't have a fixed
switching
frequency.

I doubt you'll see this since you seem to ignore me despite the fact I
know this
stuff.

Graham
Click to expand...
Careful Graham ... ! Me and thee are getting close to povoking another class
D - class T - digital amp definition war on here :)

And yes, as Graham says, that is the 'digital' (term used loosely) class T
bit in that Tripath lump.

Arfa
 
Arfa Daily wrote:

"Eeyore" <rabbitsfriendsandrelations@hotmail.com> wrote
N_Cook wrote:

So are we talking about a class D driver stage , rather than preamp in
the black lump ?

YES.

Although Tripath called it 'class T' since it doesn't have a fixed
switching frequency.

I doubt you'll see this since you seem to ignore me despite the fact I
know this stuff.

Graham

Careful Graham ... ! Me and thee are getting close to povoking another class
D - class T - digital amp definition war on here :)

And yes, as Graham says, that is the 'digital' (term used loosely) class T
bit in that Tripath lump.
Click to expand...
Years and years back, I had a demo of a Tripath unit. The sales guy went
ballistic when I tried to sinewave test it at full power.

There were more than a few problems with it, one of which is inherent to any
switching / Class D amp that results in the power rails being 'charge pumped' to
a voltage beyond nominal dependent on the load being non-resitive. I heard of
one 'PA' company that dropped Tripath totally for that or another reason.

Graham
 
Eeyore wrote:
N_Cook wrote:

So are we talking about a class D driver stage , rather than preamp in the
black lump ?

YES.

Although Tripath called it 'class T' since it doesn't have a fixed switching
frequency.
Click to expand...
Class 'T"? - WTF are they trying to say? I would've thought that Class D
would make things clear enough for anybody.

I doubt you'll see this since you seem to ignore me despite the fact I know this
stuff.
Click to expand...
Well, if he doesn't want to listen to anyone, he'll blow up a lot of
silicon, which I think is punishment enough for anybody. ;^)


--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
---^----^---------------------------------------------------------------
 
Bob Larter wrote:

Eeyore wrote:
N_Cook wrote:

So are we talking about a class D driver stage , rather than preamp in the
black lump ?

YES.

Although Tripath called it 'class T' since it doesn't have a fixed switching
frequency.

Class 'T"? - WTF are they trying to say? I would've thought that Class D
would make things clear enough for anybody.
Click to expand...
Class D is generally taken to be at a fixed switching frequency. Tripath used spread
spectrum and hence gave it another name.


I doubt you'll see this since you seem to ignore me despite the fact I know this
stuff.

Well, if he doesn't want to listen to anyone, he'll blow up a lot of
silicon, which I think is punishment enough for anybody. ;^)
Click to expand...
LOL !

Graham
 
On Thu, 07 May 2009 09:51:24 +0100, Eeyore
<rabbitsfriendsandrelations@hotmail.com>wrote:

Bob Larter wrote:

Eeyore wrote:
N_Cook wrote:

So are we talking about a class D driver stage , rather than preamp in the
black lump ?

YES.

Although Tripath called it 'class T' since it doesn't have a fixed switching
frequency.

Class 'T"? - WTF are they trying to say? I would've thought that Class D
would make things clear enough for anybody.

Class D is generally taken to be at a fixed switching frequency. Tripath used spread
spectrum and hence gave it another name.


I doubt you'll see this since you seem to ignore me despite the fact I know this
stuff.

Well, if he doesn't want to listen to anyone, he'll blow up a lot of
silicon, which I think is punishment enough for anybody. ;^)

LOL !

Graham
Click to expand...
My all digital Waller guitar amp has a tripath output inside. 100
watts from a postage stamp sized device. Nice sound and has been
reliable except for the intermixing of digital and analog grounds in
the DSP which Waller allowed me to repair under warranty 5 years ago.
All the repair involved was cutting a trace and adding a chassis
ground to the circuit.

http://i273.photobucket.com/albums/jj220/meatplow1/music/IMG00094.jpg
 
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