Emax

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????
> > M\ufffds 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\ufffds what a found: IC 14(NS32008) gets very
> hot,
> > > IC
> > > > 14 , 9 and IC 17 gets hot, also when you play
> the
> > > > keyboard there\ufffds is sound, not in scale,
> > > additionally
> > > > as you play, the menu\ufffds 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\ufffds some processor not
> doing
> > > > well its job, i don\ufffdt think i can find one of
> > > these
> > > > IC\ufffds 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
> > > the
> > > > > 5V
> > > > > > digital power ?, because last night i
> worked
> > > on
> > > > > the
> > > > > > machine, I check de purple, orange wire,
> > > > > > etcetera....
> > > > > > +12`s Volts +10\ufffds ,s volts , the yellow
> wire
> > > marks
> > > > > > +4,92 volts,....... but i cannot locate
> the
> > > pin 3
> > > > > of
> > > > > > VR1 and check +5Volts, there\ufffds a green
> wire
> > > with
> > > > > no
> > > > > > power. I made also some reseating...no
> > > success, I
> > > > > > found 3 IC`s near the Eprom heated but
> still
> > > you
> > > > > can
> > > > > > touch it with your finger not so hot...,
> so i
> > > > > > suspect
> > > > > > there`s something wrong in that zone. Is
> some
> > > > > other
> > > > > > thing to do?????
> > > > > >
> > > > > > greetings
> > > > > > Ricardo
> > > > > >
> > > > > >
> > > > > >
> > > > > > --- Wayne Griffin <ingsoc_1979@...>
> 
=== message truncated ===


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