Yamaha EMX640 mixer amp

N

N_Cook

Guest
As far as I can tell this is the basic form to the power amp - what class is
it? and in general terms the operational bounds of the biasing, a lot of
diodes? seem to be involved.
Equi-spaced font needed for this ASCII, maybe properties/mesage details or
copied into text handler with "Terminal ","Fixedsys" font or similar
(only 2 emitter resistors, on two central Tr and chokes in the other emitter
commoned connections, all left out in the below )

---------------------- + rail
| |
|/ \|
-| |-
|> <|
| |
|--------| all 2SD2560
|
\|
|-
<|
|
|---------- O/P
|
|
|-
Click to expand...
/|
|
|--|----| all 2SA1647
| |
|< >|
-| |-
|\ /|
| |
--------------------- - rail
 
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:hn2c4v$855$1@news.eternal-september.org...
As far as I can tell this is the basic form to the power amp - what class
is
it? and in general terms the operational bounds of the biasing, a lot of
diodes? seem to be involved.
Equi-spaced font needed for this ASCII, maybe properties/mesage details or
copied into text handler with "Terminal ","Fixedsys" font or similar
(only 2 emitter resistors, on two central Tr and chokes in the other
emitter
commoned connections, all left out in the below )

---------------------- + rail
| |
|/ \|
-| |-
|> <|
| |
|--------| all 2SD2560
|
\|
|-
|
|
|---------- O/P
|
|
|-
/|
|
|--|----| all 2SA1647
| |
|< >|
-| |-
|\ /|
| |
--------------------- - rail
Click to expand...

Looks like a lot of amps I see these days. Don't know for sure the "class"
but I suspect it's pretty conventional AB.

Those outputs are Darlington, by the way, so obviously there's an additional
1.2 volts to be accounted for in the biasing...

Mark Z.
 
Mark Zacharias <mark_zacharias@sbclobal.net> wrote in message
news:4b94cfb6$0$2226$c3e8da3@news.astraweb.com...
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:hn2c4v$855$1@news.eternal-september.org...
As far as I can tell this is the basic form to the power amp - what
class
is
it? and in general terms the operational bounds of the biasing, a lot of
diodes? seem to be involved.
Equi-spaced font needed for this ASCII, maybe properties/mesage details
or
copied into text handler with "Terminal ","Fixedsys" font or similar
(only 2 emitter resistors, on two central Tr and chokes in the other
emitter
commoned connections, all left out in the below )

---------------------- + rail
| |
|/ \|
-| |-
|> <|
| |
|--------| all 2SD2560
|
\|
|-
|
|
|---------- O/P
|
|
|-
/|
|
|--|----| all 2SA1647
| |
|< >|
-| |-
|\ /|
| |
--------------------- - rail







Looks like a lot of amps I see these days. Don't know for sure the "class"
but I suspect it's pretty conventional AB.

Those outputs are Darlington, by the way, so obviously there's an
additional
1.2 volts to be accounted for in the biasing...

Mark Z.
Click to expand...
Assuming its rating at 200 watts into 4 Ohms is per (non stereo) channel ,
it does not seem right that all that current goes through 2 output TOP66
devices. I've not found any date so far, mixer section not looked at yet.
Does roundel stamp on the [cb with Japanese script on top and bottom
sections and 86 12 15 across the middle mean 1986?
 
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:hn2l82$mq2$1@news.eternal-september.org...
Mark Zacharias <mark_zacharias@sbclobal.net> wrote in message
news:4b94cfb6$0$2226$c3e8da3@news.astraweb.com...
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:hn2c4v$855$1@news.eternal-september.org...
As far as I can tell this is the basic form to the power amp - what
class
is
it? and in general terms the operational bounds of the biasing, a lot
of
diodes? seem to be involved.
Equi-spaced font needed for this ASCII, maybe properties/mesage details
or
copied into text handler with "Terminal ","Fixedsys" font or similar
(only 2 emitter resistors, on two central Tr and chokes in the other
emitter
commoned connections, all left out in the below )

---------------------- + rail
| |
|/ \|
-| |-
|> <|
| |
|--------| all 2SD2560
|
\|
|-
|
|
|---------- O/P
|
|
|-
/|
|
|--|----| all 2SA1647
| |
|< >|
-| |-
|\ /|
| |
--------------------- - rail







Looks like a lot of amps I see these days. Don't know for sure the
"class"
but I suspect it's pretty conventional AB.

Those outputs are Darlington, by the way, so obviously there's an
additional
1.2 volts to be accounted for in the biasing...

Mark Z.


Assuming its rating at 200 watts into 4 Ohms is per (non stereo) channel ,
it does not seem right that all that current goes through 2 output TOP66
devices. I've not found any date so far, mixer section not looked at yet.
Does roundel stamp on the [cb with Japanese script on top and bottom
sections and 86 12 15 across the middle mean 1986?
Click to expand...
The B1647 and C2560 are pretty high-rated devices. 200 into 4 ohms doesn't
seem _too_ over rated to me.

I commonly see them in consumer audio in their higher end model surround
receivers, that is the ones rated over the standard 100 per channel, more
like 120 into 8 ohms. So as I say, 200 doesn't seem too far off, perhaps
just a bit of a stretch.

Mark Z.
 
Mark Zacharias <mark_zacharias@sbclobal.net> wrote in message
news:4b94e43f$0$24357$c3e8da3@news.astraweb.com...
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:hn2l82$mq2$1@news.eternal-september.org...
Mark Zacharias <mark_zacharias@sbclobal.net> wrote in message
news:4b94cfb6$0$2226$c3e8da3@news.astraweb.com...
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:hn2c4v$855$1@news.eternal-september.org...



Assuming its rating at 200 watts into 4 Ohms is per (non stereo) channel
,
it does not seem right that all that current goes through 2 output TOP66
devices. I've not found any date so far, mixer section not looked at
yet.
Does roundel stamp on the [cb with Japanese script on top and bottom
sections and 86 12 15 across the middle mean 1986?



The B1647 and C2560 are pretty high-rated devices. 200 into 4 ohms doesn't
seem _too_ over rated to me.

I commonly see them in consumer audio in their higher end model surround
receivers, that is the ones rated over the standard 100 per channel, more
like 120 into 8 ohms. So as I say, 200 doesn't seem too far off, perhaps
just a bit of a stretch.

Mark Z.
Click to expand...
All power devices share the same h/s 6 of these per ch, bridge rect,
7815,7915 no special treatment for those final 2 per ch. No fan assist,
large convection area out rear only. Get into the mixer later for 7 more
problems in there, so probably will find a more reliable date
 
Datecodes on TTL likely 1997 , much more likely
86, 12, 17 on this inspection ink stamp roundel so 86 is not 1986.
Amazing they could keep using on one ch as long as they did, only stopped
when an intermittant squeel got too frequent. pcb crack half the height of
the mixer board. Edge reinforced , other end drill hole crack limited now
and major traces drilled/bridged with metal , so can safely handle to deal
with all the other traces. I knew the amp had been dropped from the rear
panel bent by the tr inertia. So stove in from the front as well.
 
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