🚀 go-pugleaf

Dwight,

>After the NetModem is turned on the three lights flash as normal until
>it is warmed up.  It shows up on the Network, will connect and AT command
>works correctly.  Then in about 4 minutes the power cycles, the connection
>is lost, the lights start blinking again, etc.
>
>After another 4 minutes or so the lights go out and don't return, the 
>connection is lost.  I checked to 7805 chip inside.  It maintains 25VDC
>input and 5VDC output even after the modem dies.  It is really hot though.
>

If seems to me that there nothing really irreversably worng with it.  It 
seems that it is overheating, which stuffs up the regulator and way cut 
power to itself for a while or stop working, stuffing up the input to the 
chips.  I'm not sure, but this type of thing happened to me too, it turned 
out that by connecting some sort of heat sink (anything which takes away 
heat) to the component getting hot, helps.  This doesn't SOLVE the problem 
as such, but may provide a way around it.  In my case, I connected it to the 
case (metal) so that was fine, if you can't do this, you may wish to look 
into buying a little heat sink for it, the ones with the cooling fins, if 
you have enough room in the case that is!

The real problem is that the regulator or whatever it is, is having to 
decrease the voltage too much, in which case your power supply might be 
giving out oo much voltage, you could look into that too...

Just some suggestions.

Nathan.

In article <1992Sep4.065714.2381@lna.oz.au> randy@lna.oz.au (Randolph CHRISTOPHERS) writes:
>In article <1992Aug27.222807.13917@sequent.com> dwightj@sequent.com (Dwight Johnson) writes:
>>I need to know how to fix our NetModem.  Shiva wants over $250 to even
>>look at it.  I think it should be a one or two component replace job.
>>
>>.....  I checked to 7805 chip inside.  It maintains 25VDC
>>input and 5VDC output even after the modem dies.  It is really hot though.
>>
>Hooly dooly, thats a 20V difference. I don't think 7805's are meant for
>that sort of torture (usually a DC input of less than 10V is OK). Little 
>wonder its cooking.
>
>Randy.

There most be something wrong with your wall-mount transformer.  It should
have an output of 9V AC.  This 9V AC is put through a full-wave rectifer and
then used as the input to the voltage regulator.  If you are see 20V DC at the
input something is wrong.  You should check the output of the wall-mount.
F.Y.I. The regulator input should be somewhere about 9-10V DC depending on the
line voltage.

Chris Outzen
Manager Hardware Development
Shiva Corp