Help!
I have an old Tascam MM-200 (vintage 1994) mixer that has a bug - the stereo
effect returns (all four) have one dead channel. Can anyone help me with
it?
I have no schematic or repair data on it.

[] send response / scanned schematic to:
jetgraphics at yahoo dot com

TIA!

On Thu, 08 Jul 2004 18:51:10 -0400, jetgraphics
wrote:

Help!
I have an old Tascam MM-200 (vintage 1994) mixer that has a bug - the stereo
effect returns (all four) have one dead channel. Can anyone help me with
it?
I have no schematic or repair data on it.

I have a service manual for a M-200 "mixing console", dated Sept 1985.
It looks to have two effects return channels, which pass through U201
in each return channel. Ring any bells?

Good fortune, and report back,

Chris Hornbeck
"Have some Madiera, M'dear"

On Thu, 08 Jul 2004 18:51:10 -0400, jetgraphics
wrote:

Help!
I have an old Tascam MM-200 (vintage 1994) mixer that has a bug - the stereo
effect returns (all four) have one dead channel. Can anyone help me with
it?
I have no schematic or repair data on it.

I have a service manual for a M-200 "mixing console", dated Sept 1985.
It looks to have two effects return channels, which pass through U201
in each return channel. Ring any bells?

Good fortune, and report back,

Chris Hornbeck
"Have some Madiera, M'dear"

jetgraphics wrote:
Help!
I have an old Tascam MM-200 (vintage 1994) mixer that has a bug - the stereo
effect returns (all four) have one dead channel. Can anyone help me with
it?

Well, have you gone through with a scope and a signal generator and followed
the signal. Is it on the buss? Is it going into the makeup gain amp? Is
it coming out of the makeup gain amp?

Are all four channels handled by one quad op-amp by any chance?

I have no schematic or repair data on it.

You should be able to figure this stuff out by tracing things out by hand,
but for twenty bucks or so, Tascam will sell you a service manual so you
can save some time.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

jetgraphics wrote:
Help!
I have an old Tascam MM-200 (vintage 1994) mixer that has a bug - the stereo
effect returns (all four) have one dead channel. Can anyone help me with
it?

Well, have you gone through with a scope and a signal generator and followed
the signal. Is it on the buss? Is it going into the makeup gain amp? Is
it coming out of the makeup gain amp?

Are all four channels handled by one quad op-amp by any chance?

I have no schematic or repair data on it.

You should be able to figure this stuff out by tracing things out by hand,
but for twenty bucks or so, Tascam will sell you a service manual so you
can save some time.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Scott Dorsey wrote:

Well, have you gone through with a scope and a signal generator and
followed the signal. Is it on the buss? Is it going into the makeup gain
amp? Is it coming out of the makeup gain amp?

Are all four channels handled by one quad op-amp by any chance?

Got scope (old 40 MHz), got no signal generator.
Got visual impairment, no can see good, anyway.
Sigh.

Scott Dorsey wrote:

Well, have you gone through with a scope and a signal generator and
followed the signal. Is it on the buss? Is it going into the makeup gain
amp? Is it coming out of the makeup gain amp?

Are all four channels handled by one quad op-amp by any chance?

Got scope (old 40 MHz), got no signal generator.
Got visual impairment, no can see good, anyway.
Sigh.

jetgraphics wrote:
Scott Dorsey wrote:

Well, have you gone through with a scope and a signal generator and
followed the signal. Is it on the buss? Is it going into the makeup gain
amp? Is it coming out of the makeup gain amp?

Are all four channels handled by one quad op-amp by any chance?

Got scope (old 40 MHz), got no signal generator.

Get a signal generator, or a CD player with a tone CD on it. Or ground one
input pin to produce a hum (always a handy tone source in a pinch).

Got visual impairment, no can see good, anyway.

Then get a signal tracer instead of the scope, so you can tap a probe on
traces and listen for signal there. Not a very fashionable thing to use
any more, but very underrated if you ask me.

If you have trouble seeing the tiny pins, a headworn magnifier and _very_
bright desk lamp can help.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

jetgraphics wrote:
Scott Dorsey wrote:

Well, have you gone through with a scope and a signal generator and
followed the signal. Is it on the buss? Is it going into the makeup gain
amp? Is it coming out of the makeup gain amp?

Are all four channels handled by one quad op-amp by any chance?

Got scope (old 40 MHz), got no signal generator.

Get a signal generator, or a CD player with a tone CD on it. Or ground one
input pin to produce a hum (always a handy tone source in a pinch).

Got visual impairment, no can see good, anyway.

Then get a signal tracer instead of the scope, so you can tap a probe on
traces and listen for signal there. Not a very fashionable thing to use
any more, but very underrated if you ask me.

If you have trouble seeing the tiny pins, a headworn magnifier and _very_
bright desk lamp can help.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."