Re: Any CRT experts out there?

Sorry, did not see the other question.

There are a few different boards in the P990. The A board is the one that mounts the the CRT. There is a large horizontal board beneath the CRT that has the power supply and the FBT on it and it is called the D board. When I said "main board", I was referring to the D board.

Re: Any CRT experts out there?

I already had the caps and a DB9 connector so I thought I'd just breadboard the circuit. I didn't think I would need to use it frequently enough to need the parts permanently mounted on a PCB and I was placing an order with Digikey for some other items anyway.

Re: Any CRT experts out there?

Just an update for anybody else who may experience this problem.

I found that the 6V regulator that supplies power to the CRT heating element was only producing about 4.5V. On the Oscope it looked like a square wave with the high at about 6 and the low around 4. I have not built an ESR tester yet so I used a function generator and a oscope to test ESR on LOTS of capacitors. I replaced many on both the main board and CRT board.

In addition to a much brighter display this exercise also corrected some other display issues....

I have an old Dell P990 CRT monitor that seems to have finally given out. It's probably time to spend some $ and get an LCD, but I would like to take a shot at fixing the CRT for the fun of it.

For sometime now the monitor has appeared quite dim. I had to turn up the brightness to nearly 100%. I tried the "color return" option before the monitor finally stopped working and that did not improve the situation.

Right now when I power up the monitor the green power led cycles on and off about every second. I can hear a slight "ticking" noise keeping...

Re: Gateway 900G frustration

I got it fixed. In fact, it was probably fixed yesterday and I did not realize it.

After I replaced all the caps I checked the 5 and 12 volt signals with the board out of the monitor (no load). When I saw the 5V output oscillating I thought that was wrong and kept goofing around. It looks like I ended up blowing a fuse in the process of poking around so much. Once I replaced the fuse and tested the 5 and 12 volts signals under a load they were fine. I'm sure it was the capacitors all along.

Thanks.

Re: Gateway 900G frustration

I replaced all the 470uF with 470uF 50V, and all the 220uF with 220uF 50V. They are a collection of caps from both NTE and Xicon. I replaced the 680uF with a 680uF 50V. It's physically too big for the board to go back into the monitor, but I thought I would replace it just in case....assuming I can get this working I'll find a smaller 680uF.

Things have also changed. The 12V supply is now moving around and the 5V supply that as swinging between 3 and 5V is now swinging around 1-2V. Not sure if I've done more damage or if something is degrading....

Re: Gateway 900G frustration

Hi, I replaced all that I saw. The smallest one (the 47uF cap) was replaced also with a 47uF. When it did not work I tried a 100uF cap as someone else had done.

Re: Gateway 900G frustration

I've got the "ticking" problem coupled with the 5v supply oscillations.

I replaced all the electrolytic caps and the also tried the shunt regulator and the problem still exists. It is interesting to note that the period of the ticks was about once/second before I swapped the caps and now it is more like 2 seconds.

I'm competent, but not terribly strong with these repairs. Any advice on what components to consider or a schematic would be very helpful.

Thank you to all who offer advice.