August 31 2009

Background:

• My Modem keeps kicking me off the internet! Has this happened to you? Of course it has! Or it might.
• The DSL Modem reconnects after a few seconds, minutes, or hours.
• You call Verizon for Tech Support and they want to reformat your hard drive...Don't they always?
• You try your best to convince them that something is wrong. Do they offer to send you a know good DSL modem that you can use for a few weeks to make sure it's not your modem? No.
• During the summer the air conditioner was on and probably blew some cool air in the direction of the modem. Anyway it seemed work pretty good until the day we shut off the AC!

My Fix:

• Originally I took the cover off my DSL Modem and it seemed to make an improvement!
• Finally I had enough. Time to get serious. Well at least take a look at the capacitors in the unit.
• Here is what I found.

• A quick visual inspection of my DSL Modem showed that I had three suspected bad Electrolytic capacitors.
• C413  1000 uF 16V used on the 3.3V power supply.  (Bad Cap #1)
• C427  330uF 6.3V also on a 3.3V power supply.          (Bad Cap #2)
• C432  330uF 6.3V also on a 3.3V power supply           (Bad Cap #3)

• I spotted a few good suitable replacements from a dead motherboard I had. I tried to use caps that were from a switching power supply.

• I tried to go higher in the voltage rating if I found a replacement in my junk pile.
• I used a bigger value cap where I could not find the original value.
• I could have ordered the parts from Digi-key I suppose but then I would not be writing my story tonight! Onward!

• Cap #1: This guy shown on the operating table had a top that looked like is was going to blow. The replacement cap is shown installed.

• Cap #2: I think this was used on a separate 3.3V power supply that the first cap. Take a good look at the bottom of the cal. It's bottom was been blown out.

• Cap #3: basically the same story as cap #2.

• Here is a close up of the three little pigs. The big bad wolf (heat) must have got the best of them.

• Power up! I powered up the unit and it seem to operate normally. I measured the current to make sure I was not overloading the wall power supply.
• Current at turn on: 0.22Amps
• Current after about 30 seconds when the modem becomes active: 0.38 Amps.
• Wall transformer rating 0.6 Amps.
• NO Overload!

• Here is a big picture showing where all the caps are.

• And finally set up the modem and I was back on line!
• The next test will be to see how it behaves over the next few days.

• Time to break out the big guns.
• I measured the temperature with one of my 10 thermal estimator probes. The chips were running HOT. I then measured the input current and found it to be about 0.540 Amps. Remember the wall power supply is only rated for 0.6A! Something funny is going on.

• How much ripple is on the big input cap? Maybe it's junk. Note, I measured it after the box was cooled down and returned to it's normal current (0.420A)
  • About 1VPP! Seems like a lot.

• Add a BFC (Big Fat Cap) and see what the ripple does.
  • Ripple goes to about 300 mV.
  • Supply voltage went to about 13V from 12V

• One BFC added. Yes it has long leads I know.

• Now what if the high current is due to a thermal run away in the chips? Lets add a fan to keep things cool.

• I used a 12Volt PC fan that I had kicking around. I oiled up the bearing so it would last another lifetime.
• I next used my Dremel to cut a hole in the top of the case and them made a few holes for the screws to attach the fan.
• Next I got an old 5V pager charger to use as my power supply. Running the 12V at 5V keeps everything quiet but moves a good amount of air.
• A few tie wraps were used to secure the power cord.
• I jammed the power supply wires into the fan connector after I tinned them.

• Finally I cut some exit vents on the side to let the air out.

• Here is the final product.
• stay tuned to see if this does the job!

Got new modem...Seemed to work for a few days but them cut out the same way as the old modem.

DSL still working BUT network printer has not been working since I installed the new modem.

I have a Brother MFC-7840W Laser printer (Awesome all in one wireless laser printer!!)

I was able to browse to the IP address that the printer was on and see it's print server.

I Also ran the BRAdmin Light tool that came with the printer to see if it saw the printer. It did.

So I opened the printer menu in Windows XP and looked at the properties of the installed printer. (Ports Tab).

I tried to reinstall the printer driver and the "activatemydsl" came up as the printer name. Somehow my printer name go renamed to "activatemydsl" I wonder where that came from??? Maybe when I had to activate my dsl modem a few days ago?

I renamed the printer back , rebooted the modem and then was able to print using the original driver. But not on all my computers...until I rebooted them.