Emax

Hi:
As you said... i put my multimeter on some pins on the
microprocessor i read 4,92 4,94, some 4,91, and then 
i make a short circuit and the displays goes out, but
pressing On again i can reset. My questions is: the
potentiometer located in the Power supply  can make
some adjustment in the digital power out??????,
because i found another swithching Power supply from
another device.... who got this pot and you can make
some adjustment....
Thanks for your support
Saludos de Chile
Ricardo
          
--- ted Summers <djtbs1@...> wrote:

> The voltage readings you got are the drops across
> the diodes, not the  
> actual output of that circuit..... those are typical
> numbers for that...
> 
> Ted
> 
> On Apr 30, 2007, at 5:37 AM, cheju_99 wrote:
> 
> > Hi Ted:
> > Unfortunatelly there\ufffds no photo of the conectors ,
> but as you said
> > there\ufffds no label on the board, i expect to put
> some new photos soon..
> > Some electrical readings about components, that I
> found some strange:
> > VR1: Pin 3: 4,91 volts, pin 1: 117 Volts
> > Diodes
> > D3: 0.650 --0.834 v
> > D8: 1.538 ---0.617 v
> > D2: 0.618 --- 1.60 v
> > I don\ufffdt know if this is OK....or not????
> > Besides the above i found nothing more peculiar on
> my sick Emax....
> >
> >
> > --- In emax@yahoogroups.com, ted Summers
> <djtbs1@...> wrote:
> > >
> > > I need more description (do the connectors have
> labels next to
> > them
> > > like CN14 or J1), to tell you what the
> connectors are for. Picture
> > > Files do not show on the group email, but you
> could post them to
> > the
> > > files and then we could see what you are talking
> about, also.
> > >
> > > Thanks,
> > > Ted
> > >
> > > On Apr 29, 2007, at 1:18 AM, RICARDO JUAREZ
> wrote:
> > >
> > > > Well...
> > > > I clean all the unit,everything was removed,
> and found
> > > > nothing special, nothing but a few problems
> with some
> > > > "Light leds" in the push buttons, there was
> one with a
> > > > "cold soldering", and some contacts with
> several
> > > > wearing, I repair it with some glue and new
> metalics
> > > > contacts, ONe Question: There\ufffds a pair of
> "sort of
> > > > jacks" (white and light-Blue) in the back of
> the
> > > > keyboard plaque, in one side and the other
> side, is
> > > > there any cable attached to they??? because my
> unit
> > > > has no one........I will check the soldering
> in the
> > > > PSU...
> > > > Saludos
> > > > Ricardo
> > > >
> > > > --- Wayne Griffin <ingsoc_1979@...> wrote:
> > > >
> > > > > I agree about the 5.05V and the idea of a
> voltage
> > > > > drop
> > > > > across the digital board.
> > > > >
> > > > > orange = +12V
> > > > > yellow = +5V (5.05V)
> > > > > purple = -12V
> > > > >
> > > > > The +10V on pin 3 of Q2 is also fine because
> that's
> > > > > either to drive the DC/DC converter for the
> LCD
> > > > > backlight or maybe something pertaining to
> the
> > > > > EPROM.
> > > > > [w]
> > > > >
> > > > >
> > > > >
> > > > > --- ted Summers <djtbs1@...> wrote:
> > > > >
> > > > > > Well, my opinion is that there is an issue
> with
> > > > > the
> > > > > > power supply.
> > > > > >
> > > > > > The 4.92 volt is SUPPOSED to be at 5V. A
> little
> > > > > > variance is ok, and
> > > > > > higher (5.05V) especially in an older unit
> would
> > > > > > feed better as it
> > > > > > went across the board. 4.92 is a bit low.
> Most
> > > > > chips
> > > > > > like 4.95 at
> > > > > > least. And remember the farther you
> measure across
> > > > > a
> > > > > > board, the more
> > > > > > the volts will drop lower. In fact, if you
> knew
> > > > > the
> > > > > > correct pin to
> > > > > > test for on the farthest chip physically
> across
> > > > > the
> > > > > > board from the
> > > > > > power supply, and measure the volt reading
> on the
> > > > > 5
> > > > > > volt pin, it
> > > > > > wouldn't surprise me if it is actually
> much lower
> > > > > > than the 4.92. This
> > > > > > can cause very strange behaviour in logic
> systems.
> > > > > >
> > > > > > It is possible to attach a PC power supply
> and
> > > > > test,
> > > > > > without making
> > > > > > it "permanent". Not an ATX, but an older
> AT style
> > > > > > power supply.... I
> > > > > > would have to see schematics, but am not
> sure why
> > > > > > there would be a 10
> > > > > > volt, it seems that should be twelve. If
> the power
> > > > > > supply is putting
> > > > > > out 10v on a 12v line, then that would be
> another
> > > > > > issue.
> > > > > >
> > > > > > Be aware that power supplies have what are
> called
> > > > > > 'rails'. Each rail
> > > > > > is a separate voltage. So the power supply
> may
> > > > > have:
> > > > > > 1 x 5 Volt rail
> > > > > > 2 x 12 volt rail
> > > > > >
> > > > > > for an example. One 12Volt rail could be
> ok, and
> > > > > the
> > > > > > other bad, then
> > > > > > the bad side can pull down the power on
> the good
> > > > > > one.
> > > > > >
> > > > > > I looked at the power supply in my emax
> when I
> > > > > > first got it. They
> > > > > > used diodes to "crowbar" the voltage
> regulation
> > > > > > circuit. Not an
> > > > > > uncommon practice back then, but not done
> often
> > > > > now
> > > > > > (there are better
> > > > > > ways to do this). What I did on my power
> supply
> > > > > when
> > > > > > I first got the
> > > > > > emax was remove it, and resoldered all the
> > > > > > connections to the parts
> > > > > > on the power supply. There were a couple
> of "cold
> > > > > > solders" which are
> > > > > > solders that have small cracks in them
> (sometimes
> > > > > > require a
> > > > > > magnifying glass to see them). They will
> arc and
> > > > > > connect part of the
> > > > > > time, then lose connection momentarily at
> which
> > > > > > point the circuit is
> > > > > > broken and no longer works properly. This
> could
> > > > > > cause the lower power
> > > > > > output as well as the strange behaviour.
> You can
> > > > > > resolder all the
> > > > > > parts on the power supply, then if that
> doesn't
> 
=== message truncated ===


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