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Re: Cracks in EDP

At 12:11 PM -0800 12/10/00, stevek@msidata.com wrote:
>... My EDP seems to be pretty sensitive to heat. ...
>I have a similar problem, but my EDP makes LOUD and UGLY noises when it 
>heats.  I have been checking for what seem to be the hot components on the
>circuit board and have isolated "excess heat" to the voltage converter
>(power supply) IC's.  I have not tried to replace them yet but may attempt
>it soon.  I had this problem some time ago and send the unit in for 
>They replaced the memory chips and the EDP worked better for a while but 
>problem has returned.  Any other ideas as to how to solve the problem 
>be appreciated.
>Steve Kraninger

All recently built Echoplexes (the past two years or so) use a different
type of voltage regulator that generates practically no heat. In older
units, the linear regulators used to supply +5V to the digital section got
quite hot. That sounds like what you are experiencing. If you want to
update your Echoplex with the newer regulator and you've got some soldering
skils, it is pretty easy. (if you don't have such skills, find a decent
electronics tech to do it for you or have gibson do it. I'm pretty sure
Shane Radtke at Gibson's service dept knows about this one.)

You need to change the two +5V linear regulators at the back of the unit to
a switching regulator. These are 5 volt regulators U40, and U28. When you
take the top off the echoplex, they will be the two in the back attached to
the heatsink. These power two 5 volt digital sections.

The part used in current Echoplex production to replace these is the Power
Trends (http://www.powertrends.com/) PT5101N 5V switching regulator. You
should be able to get this part from Digikey (www.digikey.com). This part
is a drop-in replacement for the standard 3-pin linear regulators, and they
work great. You can actually use one of these to replace both of the linear
regulators, and it works just fine. This is what they do in production now.

You need to take the PCB out of the chassis to do it. To do that, unscrew
the front panel, unscrew the pcb, unscrew the heat sink from the back, and
remove the nuts from the jacks on the back. It should pop right out. What
you want to do is unscrew the regulators from the heatsink. Desolder and
remove both U28 and U40, the linear regs. Take the heat sink out altogether
since it will be in the way, and you won't need it anymore.

Solder the PT5101 into one of the regulator spots (the left one is a good
choice). The PT5101 is pin compatible with the linear regs, so there should
be no trouble with that. Now solder a wire from it's output pin (pin 3, on
the right when looking at the front of the part) to the output hole (pin 3
again) for the other regulator location. Use reasonably thick wire,
probably 18 gauge is ok. This way the PT5101 will be supplying power for
both the +5V rails the old regulators powered. Put the PCB back in the
chassis and screw it back together. Now power it up and make sure it works!
You should see the Echoplex runs practically at room temperature now, and
hopefully that cures the trouble.

Let me know if you have questions.


Kim Flint                     | Looper's Delight
kflint@loopers-delight.com    | http://www.loopers-delight.com