Emax

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´s no photo of the conectors , but as you said
> there´s 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´t 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´s 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
> > > > seem
> > > > > to help, get the
> > > > > PC power supply and hook in place of the original
> > > > > supply to do a test...
> > > > >
> > > > > Just a couple of thoughts.
> > > > > But what do I know. Having worked as a repair tech
> > > > > for 17 years on
> > > > > electronic equipment.... I don't know anything ;-)
> > > > >
> > > > > Thanks,
> > > > > Ted
> > > > >
> > > > >
> > > > >
> > > > >
> > > > > On Apr 26, 2007, at 8:51 PM, RICARDO JUAREZ wrote:
> > > > >
> > > > > > Yep!,I still need a method for verify the 5v of
> > > > > the
> > > > > > digital, Why we need to measure VR1?????, and
> > > > how
> > > > > you
> > > > > > do that????
> > > > > > Más Saludos
> > > > > > Ricardo
> > > > > >
> > > > > > --- ted Summers <djtbs1@...> wrote:
> > > > > >
> > > > > > > That IC is still available (just google it-
> > > > > someone
> > > > > > > will sell you a
> > > > > > > single one- may have to do a bit of email to
> > > > get
> > > > > it)
> > > > > > > and one bad IC
> > > > > > > can cause others ICs to heat up as well....
> > > > > > >
> > > > > > > But I would still verify the Power Supply
> > > > > first.....
> > > > > > >
> > > > > > > Thx,
> > > > > > > Ted
> > > > > > >
> > > > > > > On Apr 26, 2007, at 6:28 AM, RICARDO JUAREZ
> > > > > wrote:
> > > > > > >
> > > > > > > > Hi!:
> > > > > > > > Here´s what a found: IC 14(NS32008) gets
> > > > very
> > > > > hot,
> > > > > > > IC
> > > > > > > > 14 , 9 and IC 17 gets hot, also when you
> > > > play
> > > > > the
> > > > > > > > keyboard there´s is sound, not in scale,
> > > > > > > additionally
> > > > > > > > as you play, the menu´s system changes going
> > > > > from
> > > > > > > > everything to everything
> > > > > > > (master---traspose---change
> > > > > > > > patches---select, etc)even performs a
> > > > sequence
> > > > > on
> > > > > > > the
> > > > > > > > diskette and blocks the keyboard....tottally
> > > > a
> > > > > > > mess.
> > > > > > > > When you push a button in the panel the
> > > > system
> > > > > > > crash
> > > > > > > > and no sound and changes, hanging the last
> > > > > > > > note.....despite all this stuff, the patches
> > > > > > > sounds
> > > > > > > > very good. Really there´s some processor not
> > > > > doing
> > > > > > > > well its job, i don´t think i can find one
> > > > of
> > > > > > > these
> > > > > > > > IC´s nowadays, is there any method for
> > > > > reseting
> > > > > > > this
> > > > > > > > devices.
> > > > > > > > Saludos
> > > > > > > > ricardo
> > > > > > > >
> > > > > > > > --- Wayne Griffin <ingsoc_1979@...>
> > > > > wrote:
> > > > > > > >
> > > > > > > > > What are the IC #'s on the chips? What do
> > > > > the
> > > > > > > chips
> > > > > > > > > say on them??? Did you also reseat
> > > > > *everything*,
> > > > > > > > > todos
> > > > > > > > > on the second board, attached to the
> > > > > > > motherboard?
> > > > > > > > > [w]
> > > > > > > > >
> > > > > > > > > --- RICARDO JUAREZ <cheju_99@...>
> > > > > wrote:
> > > > > > > > >
> > > > > > > > > > Wayne:
> > > > > > > > > > Could you be more specific about the
> > > > test
> > > > > of
> > > >
> > > === message truncated ===
> > >
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> 



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