Hi juanvivo.. it was me that posted the problems with an MC5 model.

In your placa2 pic, there is a diode near the 12 volt power input connector,
marked D7. It may be worthwhile to test the diode for shorted condition..
diode test with a DMM, or ohms with an analog meter.

Since you mentioned that the T3 has no continuity from A to B, that
indicates that the transformer/inductor is (likely burned) open.
The inductor will need to be replaced, but could be jumpered from A to B for
testing purposes.
Placing a jumper across T3 terminals A to B will restore continuity for the
positive (+) side of the external power supply.

If you use a low amperage fuse in the external power supply lead, you should
be able to proceed with testing/checking for voltages on the circuit board.
I would expect that connection of all of the cables and the LCD display
would be required to proceed.

The Sony power supply for these models is a regulated 12V supply, so an
unregulated power supply (transformer/rectifiers) wouldn't be the best
choice for this unit.
A high capacity 12V battery or power supply may cause more damage if the
power leads don't include a low current fuse.

In the future, for trying equipment using external power supplies, it's a
good practice to always have a fuse in the power lead.
I was surprised that the MC5 model had no internal fuse devices, as Franc
made clear to me.

Also for future testing purposes, if you're not sure which connector contact
is for the negative (-) of the external power supply, many times it will be
the contact which shows direct connection to the unit's connectors such as
the shell/shield of RCA jacks (inputs or outputs) intended to be connected
to other equipment.

These circuit boards are fairly complex and without a service manual, all I
was able to do was hunt for defective (simple) components.

--
Cheers,
WB
..............


"juanvivo" wrote in message
...

Hi all. It's the first time I go into the forum and I congratulate all
of this information I see that you have.

A few days ago feed the recorder with reversed polarity (positive to
negative and negative to positive), and has stopped working.

I searched unsuccessfully information about a similar case, I also
sought information from the MC5, if I could be of some use, and that's
when you get to this forum. I was reading this post:
http://tinyurl.com/b97ds7x

I could not find any electric scheme, nor any repair manual, or any
clues to try to discover which was broken by reversing the polarity.

I have some pictures of the board:

http://www.juanvivo.com/images/placa1grande.jpg
http://www.juanvivo.com/images/placa2grande.jpg

some people have told me that the T3 component that appears next to the
power connector ppuede been damaged. I do not know what has value ...

[image:
http://aeromodelismovirtual.com/atta...= 1360141242]

besides the pins B, C and D have continuity.

can you help me? know any repair manual? some scheme? images?

I thank you in advance for your time.

greetings




--
juanvivo