Speaker protector on Soundlab SP 800 amp, 2002

N

N_Cook

Guest
Anyone familiar with this amp? worked for years with the present owner but
there is a quantity of circuit , each channel , that has been removed. A
"friend" decided to short a speaker line to give the current fault , but I'm
faced with a lot of post-production modification that does not look made by
the manufacturer.
Cropped tr legs and desoldered Rs,Cs, 4Tr,7R,2C all x2. Removed at
manufacture or previous owner?
Leaving this circuit in place with 2 Triac/scr. Unknown TO92 size SCR (on
overlay) marked (unclear on each channel examples)
08D
09
2 lines from the disconnected circuitry went to the left and rightmost pins
of that SCR. Nothing at any time to the centre pin. C is actually 2 back to
back 220uF, 50V for pseudo unpolarised C.
May need to go into message source for equal space font for the following


o-------------------------------|---o Speaker
| .-.
| | |
| | | 10K
|BTB24-600 '-'
' |
_|_/o-------------o o o
V_A SCR |
| |
| |
| |
| |
| ---
| --- 110uF,100V
| |
o------'-------------------------------o Ground


Can anyone identify the SCR ?
Given a nominal one there, in the correct orientation , can the scr act as a
diac? or maybe erroneous overlay marking. Can whole cct act as a crowbar
speaker protector in event of amp failure to DC output.?
 
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:h7ljds$38d$1@news.eternal-september.org...
Anyone familiar with this amp? worked for years with the present owner but
there is a quantity of circuit , each channel , that has been removed. A
"friend" decided to short a speaker line to give the current fault , but
I'm
faced with a lot of post-production modification that does not look made
by
the manufacturer.
Cropped tr legs and desoldered Rs,Cs, 4Tr,7R,2C all x2. Removed at
manufacture or previous owner?
Leaving this circuit in place with 2 Triac/scr. Unknown TO92 size SCR (on
overlay) marked (unclear on each channel examples)
08D
09
2 lines from the disconnected circuitry went to the left and rightmost
pins
of that SCR. Nothing at any time to the centre pin. C is actually 2 back
to
back 220uF, 50V for pseudo unpolarised C.
May need to go into message source for equal space font for the following


o-------------------------------|---o Speaker
| .-.
| | |
| | | 10K
|BTB24-600 '-'
' |
_|_/o-------------o o o
V_A SCR |
| |
| |
| |
| |
| ---
| --- 110uF,100V
| |
o------'-------------------------------o Ground


Can anyone identify the SCR ?
Given a nominal one there, in the correct orientation , can the scr act as
a
diac? or maybe erroneous overlay marking. Can whole cct act as a crowbar
speaker protector in event of amp failure to DC output.?
Click to expand...
Looks like a DC crowbar circuit. Don't immediately recognise that particular
device, but general convention for type numbers on SCRs and triacs, would
suggest maybe a 24 amp 600v rating ?

Arfa
 
On Wed, 2 Sep 2009 14:04:25 +0100, "Arfa Daily"
<arfa.daily@ntlworld.com>wrote:

"N_Cook" <diverse@tcp.co.uk> wrote in message
news:h7ljds$38d$1@news.eternal-september.org...
Anyone familiar with this amp? worked for years with the present owner but
there is a quantity of circuit , each channel , that has been removed. A
"friend" decided to short a speaker line to give the current fault , but
I'm
faced with a lot of post-production modification that does not look made
by
the manufacturer.
Cropped tr legs and desoldered Rs,Cs, 4Tr,7R,2C all x2. Removed at
manufacture or previous owner?
Leaving this circuit in place with 2 Triac/scr. Unknown TO92 size SCR (on
overlay) marked (unclear on each channel examples)
08D
09
2 lines from the disconnected circuitry went to the left and rightmost
pins
of that SCR. Nothing at any time to the centre pin. C is actually 2 back
to
back 220uF, 50V for pseudo unpolarised C.
May need to go into message source for equal space font for the following


o-------------------------------|---o Speaker
| .-.
| | |
| | | 10K
|BTB24-600 '-'
' |
_|_/o-------------o o o
V_A SCR |
| |
| |
| |
| |
| ---
| --- 110uF,100V
| |
o------'-------------------------------o Ground


Can anyone identify the SCR ?
Given a nominal one there, in the correct orientation , can the scr act as
a
diac? or maybe erroneous overlay marking. Can whole cct act as a crowbar
speaker protector in event of amp failure to DC output.?



Looks like a DC crowbar circuit. Don't immediately recognise that particular
device, but general convention for type numbers on SCRs and triacs, would
suggest maybe a 24 amp 600v rating ?

Arfa
Click to expand...
I've seen that in some of the higher end older high power Marantz amps
if memory serves. It's a crowbar to shunt DC from a shorted final. The
BTB24 is a Triac. Use a 25 amp 800 volt for replacement.
 
Meat Plow <meat@petitmorte.net> wrote in message
news:33ihu2.h8o.19.2@news.alt.net...
On Wed, 2 Sep 2009 14:04:25 +0100, "Arfa Daily"
arfa.daily@ntlworld.com>wrote:


"N_Cook" <diverse@tcp.co.uk> wrote in message
news:h7ljds$38d$1@news.eternal-september.org...
Anyone familiar with this amp? worked for years with the present owner
but
there is a quantity of circuit , each channel , that has been removed.
A
"friend" decided to short a speaker line to give the current fault ,
but
I'm
faced with a lot of post-production modification that does not look
made
by
the manufacturer.
Cropped tr legs and desoldered Rs,Cs, 4Tr,7R,2C all x2. Removed at
manufacture or previous owner?
Leaving this circuit in place with 2 Triac/scr. Unknown TO92 size SCR
(on
overlay) marked (unclear on each channel examples)
08D
09
2 lines from the disconnected circuitry went to the left and rightmost
pins
of that SCR. Nothing at any time to the centre pin. C is actually 2
back
to
back 220uF, 50V for pseudo unpolarised C.
May need to go into message source for equal space font for the
following


o-------------------------------|---o Speaker
| .-.
| | |
| | | 10K
|BTB24-600 '-'
' |
_|_/o-------------o o o
V_A SCR |
| |
| |
| |
| |
| ---
| --- 110uF,100V
| |
o------'-------------------------------o Ground


Can anyone identify the SCR ?
Given a nominal one there, in the correct orientation , can the scr act
as
a
diac? or maybe erroneous overlay marking. Can whole cct act as a
crowbar
speaker protector in event of amp failure to DC output.?



Looks like a DC crowbar circuit. Don't immediately recognise that
particular
device, but general convention for type numbers on SCRs and triacs, would
suggest maybe a 24 amp 600v rating ?

Arfa


I've seen that in some of the higher end older high power Marantz amps
if memory serves. It's a crowbar to shunt DC from a shorted final. The
BTB24 is a Triac. Use a 25 amp 800 volt for replacement.
Click to expand...
Not the TO220 one, I have full data on those
The problem is the TO92 little one
marked
08D
09
that I cannot identify as small SCR or diac in a 3 pin package, represented
as 3 dots, marked SCR in the ASCII
 
looks as though someone else has been here with a different amp

http://forum.allaboutcircuits.com/showthread.php?t=23271

... The schematic calls this burnt component a "triac driver sbs bv thresh"
and on its twin (in the non shorted channel) its only labeled "08d 25". This
is in the protection circuit of the amplifier which unloads the outputs if
there is a problem.

....
This is a 3 leaded device btw

so the 09 in my case and 25 for him is probably datecode

googling about ,perhaps a DIAC08D, would that be an 8V diac ? sounds about
right value of bilateral switch for a 400 W amp into 4R


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/
 
From that previous thread and mention of
MBS4993
I downloaded that datasheet and it looks as though a sort of Darlington
triac arrangement in the soundlab amp
 
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:h7ljds$38d$1@news.eternal-september.org...
Anyone familiar with this amp? worked for years with the present owner but
there is a quantity of circuit , each channel , that has been removed. A
"friend" decided to short a speaker line to give the current fault , but
I'm
faced with a lot of post-production modification that does not look made
by
the manufacturer.
Click to expand...
I normally charge an engineering fee for equipment that isn't supported and
not obvious. I won't spend more time on it than the customer can pay.
Engineering projects and prototypes require investors.
 
The amp channel failed to s/c , knocking out fuse, so speaker protector did
not
come into play.

The way to confirm the identity of this "08D" device is to
remove one and check for a switch action , at about 8V, on a current linited
bench ps.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/
 
On Wed, 2 Sep 2009 16:17:11 +0100, "N_Cook" <diverse@tcp.co.uk>wrote:

Meat Plow <meat@petitmorte.net> wrote in message
news:33ihu2.h8o.19.2@news.alt.net...
On Wed, 2 Sep 2009 14:04:25 +0100, "Arfa Daily"
arfa.daily@ntlworld.com>wrote:


"N_Cook" <diverse@tcp.co.uk> wrote in message
news:h7ljds$38d$1@news.eternal-september.org...
Anyone familiar with this amp? worked for years with the present owner
but
there is a quantity of circuit , each channel , that has been removed.
A
"friend" decided to short a speaker line to give the current fault ,
but
I'm
faced with a lot of post-production modification that does not look
made
by
the manufacturer.
Cropped tr legs and desoldered Rs,Cs, 4Tr,7R,2C all x2. Removed at
manufacture or previous owner?
Leaving this circuit in place with 2 Triac/scr. Unknown TO92 size SCR
(on
overlay) marked (unclear on each channel examples)
08D
09
2 lines from the disconnected circuitry went to the left and rightmost
pins
of that SCR. Nothing at any time to the centre pin. C is actually 2
back
to
back 220uF, 50V for pseudo unpolarised C.
May need to go into message source for equal space font for the
following


o-------------------------------|---o Speaker
| .-.
| | |
| | | 10K
|BTB24-600 '-'
' |
_|_/o-------------o o o
V_A SCR |
| |
| |
| |
| |
| ---
| --- 110uF,100V
| |
o------'-------------------------------o Ground


Can anyone identify the SCR ?
Given a nominal one there, in the correct orientation , can the scr act
as
a
diac? or maybe erroneous overlay marking. Can whole cct act as a
crowbar
speaker protector in event of amp failure to DC output.?



Looks like a DC crowbar circuit. Don't immediately recognise that
particular
device, but general convention for type numbers on SCRs and triacs, would
suggest maybe a 24 amp 600v rating ?

Arfa


I've seen that in some of the higher end older high power Marantz amps
if memory serves. It's a crowbar to shunt DC from a shorted final. The
BTB24 is a Triac. Use a 25 amp 800 volt for replacement.

Not the TO220 one, I have full data on those
The problem is the TO92 little one
marked
08D
09
that I cannot identify as small SCR or diac in a 3 pin package, represented
as 3 dots, marked SCR in the ASCII
Click to expand...
Oh ok. Maybe look up some triac model circuits and see if you can find
something similar. Either Fairchild or Motorola should have some
errata you could use.
 
On Wed, 2 Sep 2009 17:11:43 +0100, "N_Cook" <diverse@tcp.co.uk>wrote:

From that previous thread and mention of
MBS4993
I downloaded that datasheet and it looks as though a sort of Darlington
triac arrangement in the soundlab amp
Click to expand...
So it's an SBS Diode Thyristor. Looks like you've identified it.
 
Another oddity with this amp. Each channel has one floating, nominal zero
DC, connected to true ground by a 50 ohm NTC thermistor, why thermistor ?.

The missing circuitry may relate to fan proportional control of 1 or 2 fans
going by overlays.
Only one , on constantly, in this version. But why the 2 DC lines back from
the output on each channel. This is an all N-channel mosfet amp. Can they
have a DC offset if driven hard?

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