AQ 2200

[Deadly Sones]

lol, thanks. I figured it out afterward. Sawtooth looks fine. So what next? If I ground pin 4, pin 1 will still drive it to shut down right? Wish I could figure out why pin 1's high.... I realize that pin 3 of the comparator is causing it, but I can't seem to figure out why...

[Perry Babin]

Connect a jumper between pins 4 and 14 of the ka7500. Does it still go into protect. Does pin 1 ever go above a fraction of a volt?

[Deadly Sones]

Connected a jumper from 4 to 14. Did not come out of protect and the voltage on pin 1 remained the same 6v.

[Perry Babin]

What is the DC voltage measured directly across R4A and R29B?

[Deadly Sones]

With or without the jumper? Without the jumper both have 0vdc across the resistors. If I measure from one to the other I get 9.5vdc. If I hold the leads there, voltage slowly drops. It dropped down to 5.5v before my arms got tired, lol

I did check them earlier for resistance. They are both good. R4A = 46.9K (47K) and R29B = 4.69K (4.7k)

[Perry Babin]

Check them with the jumper in place and also confirm that the voltage on pin 3 is still higher than on pin 2 on IC2.

[Deadly Sones]

Both R4A and R29B have approx. 0.020v across them with the jumper installed.

The Pin 2 on IC 2 is still 2.473v, pin 3 was 3v and again as I hold the lead on the pin it slowly drains until it hits pin 2 voltage. Then it jumps down to 2.23v, then flashes to 2.34v, then jumps back to 2.49 and slowly goes back down to 2.42 and back to 2.49 over and over. IF I leave the lead off the pin for awhile and then reattach it, it shows that the voltage slowly rises on its own to over 3v again (depending on how long its powered up and the pin is not connected to ground through the meter).

[Perry Babin]

Remove IC2. Leave the jumper in place between pins 4 and 14 on the 7500. Post the voltage on all of the pads for IC2.

[Deadly Sones]

K, will do... to be continued tomorrow after work. Thanks Perry.

[Deadly Sones]

OK! I have the following readings with IC2 removed and the jumper from pin 4 to pin 14.

Pad 1: 8.42v (high?)
Pad 2: 2.473v
Pad 3: 0.028v (not fluctuating like it was, but every time I check it, keeps climbing. .058v, .090v, .126v, .151 right now - about 15 min powered up with no IC2)
Pad 4: 0.000v
Pad 5: 1.233v
Pad 6: 3.270v
Pad 7: 8.41v (high?)
Pad 8: 12.5v

For easy comparison... my old readings with IC2 installed were:

IL393
Pin 1: 6.60 (high)
Pin 2: 2.473
Pin 3: Started out @ 4+v and as I held the lead on it, the voltage slowly went down to 2.43v (lower than pin 2) then will jump up above to around 2.6or 2.7v then slowly go back down over and over. climb and drop, climb and drop. Whats up with this?
Pin 4: 0.00v
Pin 5: 1.025v
Pin 6: 3.096v
Pin 7: 0.118v (low?)
Pin 8: 12.64v

So basically Pin/pad 1 went even higher and pad 7 went from low to just as high as pin 1??? and pin/pad 3 dropped drastically. I just checked the voltage on pad 3 again, now its up to 0.370v and if I hold the lead on it, it does start to drain down the voltage...