Emax

the wine is caused by the inverter chip either the back light is playing up or the inverter is on its way out also the inverter is from the 5v line so i would say the 5v regulator caps are not holding there charge 
but with out an oscillascope to test you will have to replace all caps as you wont know which ones are at fault change to 105oc grade as these suffer less from heat exhuastion which is the biggest fault for caps dying
  ----- Original Message ----- 
  From: Donavan 
  To: emax@yahoogroups.com 
  Sent: Friday, July 10, 2009 6:44 AM
  Subject: Re: [emax] Power Supply Voltage Question





  Hey Guys thanks for the info.

  Ted, usually when I have needed to fix things the metal did take on a dull bluish tint so I'll take a look for that.

  Jammie, a quick check on oscilloscopes puts them at much more than the cost of a new psu. Perhaps just replacing the caps would be a more cost effective and long term solution.

  The vexing part is that the Emax has now been on and functioning for the last 4 hours with no problem. Also, the ambient room temperature is 73 degrees fahrenheit which rules out my hypothesis of it being heat related. 

  Well, actually I just unplugged the headphones from the right jack and into the left jack and the LCD went corrupt and started to whine. Unplugged the unit for 4 minutes to discharge the caps, and unplugged the headphones and turned it back on with the same problem. Unplugged and waited for 13 more minutes and the LCD was back on and sound was fine. Plugged the headphone into left, into right and back into left and the LCD cut out but sound was still there and there was no whine.

  OK, I read the manual thinking maybe these audio out plugs were not hot swappable and it does say in the "instant gratification" section to plug into the outputs and then turn on. But I just did that from right, on, played OK, off, left stereo, on played OK, off, right mono, on LCD corrupt and the whine.

  This is a tricky one. What are you thoughts? Should I just replace the caps, or the whole PSU, is that the likely cause here?

  Thanks
  Patrick

  ________________________________
  From: Ted Summers <djtbs1@...>
  To: emax@yahoogroups.com
  Sent: Thursday, July 9, 2009 8:19:46 PM
  Subject: Re: [emax] Power Supply Voltage Question

  My problem was the AC connector (blue and brown) right on the power 
  supply. The connector was white (but discolored brown as it was burnt 
  up). When looking at the pins they were heavily oxidized or burnt so 
  looked the metal was "flat" or matte, not shiny / gloss at all- 
  somewhat "blackened" I can't really describe it better than that.

  If you fix equipment, you know what burned pins look like. If you 
  don't fix equipment it can be hard to describe....

  Thx,
  Ted

  On Jul 9, 2009, at 6:02 PM, jammie wrote:

  11.9 is fine remember it has a tolerance of + or - 10% its usually the 
  currant side is the problem or ripple from the ripple caps you need to 
  have an oscilliscope to test for the ripple
  ----- Original Message -----
  From: Donavan
  To: emax@yahoogroups. com
  Sent: Friday, July 10, 2009 1:25 AM
  Subject: Re: [emax] Power Supply Voltage Question

  Hi Ted,

  Are you referring to the three pins coming form the AC receptacle: the 
  green to the ground screw, and the blue and brown that go to the 
  Toroid->power switch->AC IN?

  Do you recall where the problem was in the chain I described above?
  Do you have any insight into the voltage variance? Initially +11.9 
  seems "close enough", but I know there are some components that draw 
  0.02 and that missing 0.1 could be enough to cause a cascading problem.

  Also, just testing it now I had head phones plugged into Left Out and 
  as soon as I unplugged the head phones the LCD went out with some 
  residual corruption. I turned the Emax off and back on and the screen 
  was fine. I tried this test two more times and I started to get the 
  whine from the LCD screen (or a component right next to it).

  Now the forth time I turn it on the screen is off/corrupt from the 
  start, the whine is still there but the disk loads and I still get 
  audio.

  The fifth time I turn it off and back on the screen is just off 
  completely, the whine is there (gets louder the long the unit is on), 
  the floppy won't load completely and all the LEDs except the one at 
  Record/Preset Management, Dynamic Allocation, Load All and Enter are 
  on, and I get no audio of course.

  My assumption is that the voltage variance is causing this negative 
  effect depending on certain variables, such as heat given that atoms 
  can move around and the atoms can also hold more electrons, disrupting 
  the flow of electrons through the conductor.

  Thanks for the help
  Patrick

  ____________ _________ _________ __
  From: Ted Summers <djtbs1@gmail. com>
  To: emax@yahoogroups. com
  Sent: Thursday, July 9, 2009 6:22:08 AM
  Subject: Re: [emax] Power Supply Voltage Question

  My emax rack did this and it turned out to be a bad connection to the
  power supply on the AC connector.

  Regards,
  Ted

  On Jul 9, 2009, at 12:17 AM, Donavan wrote:

  Hi guys,

  My Emax hasn't been function again lately. I saw a posting by Jimmy
  Moore with a link to a german site about using an AT PSU. The
  description of the LCD corrupting and LED blinking is what struck me.
  My LCD goes blank, sometimes with some corrupt text visible, there is
  a whine that is comeing from the area of the keyboard by the LCD, and
  also all the LEDs light up and a CRC message can appear though this
  happens inconsistently.

  My question is what is the acceptable voltage variance? The
  diagnostics document I have say the VR1 can have +/- 5% variance, so
  on the required +5VDC a range of 4.75-5.25 is with in specs.

  Also, someone mentioned that the LCD (emulator_island? ) that the LCD
  can make this whine, but to your knowledge will this cause the other
  problems?

  Thanks

  Emax Specs
  Verify +12V on orange wire.

  Verify +SV on yellow wire.

  Verify -l2V on purple wire.

  Verify + 10V on pin 3 of Q2.

  My Test Results20DCV meter setting
  At psu connector at board connector
  orange 11.94V 11.94V
  purp -11.9V -11.9V
  yellow 4.96V 4.94V

  Floppy
  orange 11.94 Yellow 4.94

  200m meter setting
  Floppy
  green - 41 blue/Purp/Wht - 5.1

  Q2 visible circuit path pin
  1 - 10.04
  2-11.93

  3-10.72

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