How to check VCR system controller chip M37777MAA?

[Robert Miller]

Hello All,

I'm troubleshooting a JVC HR-VP654U VCR which was damaged by a surge after a
power outage. It seems to have good supply voltages at the regulator but
comes up in the ON state and is otherwise dead to button presses on the
front panel or remote. Does anyone know how to do a quick status check of
the system controller (label: M37777MAA-1C2GP). It's a proprietary version
of a 100-pin, quad flatpack, Mitsubishi uC that I don't have a datasheet
for. All I'm looking for is pin numbers for supply voltages, ground, clock,
etc.

Thanks for any suggestions, -R. Miller

 

[The Al Bundy]

"Robert Miller" <see.post.for.real.address@pacbell.net> wrote
news:hKl7c.41057$lb1.22146@newssvr25.news.prodigy.com...

Hello All,

I'm troubleshooting a JVC HR-VP654U VCR which was damaged by a surge after
a
power outage. It seems to have good supply voltages at the regulator but
comes up in the ON state and is otherwise dead to button presses on the
front panel or remote. Does anyone know how to do a quick status check of
the system controller (label: M37777MAA-1C2GP). It's a proprietary version
of a 100-pin, quad flatpack, Mitsubishi uC that I don't have a datasheet
for. All I'm looking for is pin numbers for supply voltages, ground,
clock,
etc.

Thanks for any suggestions, -R. Miller

There must be a crystal connected to such uC, it still oscillates?

Al

 

[Robert Miller]

Thanks, Al.

I tried looking for a clock already but the results weren't conclusive.
There is a crystal near the chip that's oscillating at about 35MHz. It shows
up at one of the pins of the uC as a 3.5V sine wave. But I have no idea
whether that's the right pin or voltage or whether it's supposed to be a
square wave or not. And I can't see sign of activety on any other pins of
the uC so it still seems as though it's dead or inactive for some reason.
I'm afraid I've gone as far as I can working "seat of the pants." That's why
I was hoping that someone might have spefici knowledge of the uC chip or
that model VCR. Thanks for your help, though...

-R. Miller

"The Al Bundy" <the_al_bundy@*^no-spam!^*hotmail.com> wrote in message
news:c3kpfj$mde$1@news2.tilbu1.nb.home.nl...

There must be a crystal connected to such uC, it still oscillates?

Al

 

[David]

No schematic available to give you the locations. But the problem is most
likely one of two things, the reset circuit is locked up, or the 60hz clock
signal the micro gets more or less directly off the ac line is missing.
Both are common on JVC vcrs and tv sets after power surge/ aka lightning
damage.

Your only real option is to buy the service manual, if it is still
available, from JVC.

"Robert Miller" <see.post.for.real.address@pacbell.net> wrote in message
news:hKl7c.41057$lb1.22146@newssvr25.news.prodigy.com...

Hello All,

I'm troubleshooting a JVC HR-VP654U VCR which was damaged by a surge after
a
power outage. It seems to have good supply voltages at the regulator but
comes up in the ON state and is otherwise dead to button presses on the
front panel or remote. Does anyone know how to do a quick status check of
the system controller (label: M37777MAA-1C2GP). It's a proprietary version
of a 100-pin, quad flatpack, Mitsubishi uC that I don't have a datasheet
for. All I'm looking for is pin numbers for supply voltages, ground,
clock,
etc.

Thanks for any suggestions, -R. Miller