Help with repair of Turbo Express

[thesteve]

both sides?
to ground..........
so you lost a ground

[jelloslug]

both sides?
to ground..........
so you lost a ground

Positive lead on each of the the capacitor leads, negative lead on the negative lead from battery connection.

[thesteve]

lol
you need to be checking + lead to - lead on each cap

[jelloslug]

lol
you need to be checking + lead to - lead on each cap

I'm sure I did that too and got nothing.  I'll be home in 20 minutes or so and I can take a look at it then.  I'm really suspect of the area where the power comes in from the AC jack and the battery connection.  The AC jack was toast and had burnt the board and ruined the pads where it was soldered on.  I removed my repair from the area just to be sure that it was not shorting out anything but there was no change.

[jelloslug]

It does seem like I have indeed lost ground.  I'm assuming that all the shielding is hooked to ground.  Are one of those pads a safe place to hook up a temporary ground to test with? I don't want to compoud the problem by nuking something else.

[thesteve]

yes the shields are ground
power comes in, goes through filter, to power jack, to filter, to fuse, to switch.
from switch it splits to 5V supply, -24V supply and backlight inverter

[jelloslug]

yes the shields are ground
power comes in, goes through filter, to power jack, to filter, to fuse, to switch.
from switch it splits to 5V supply, -24V supply and backlight inverter

With the new ground I now get the backlight and light static in the headphone jacks and nothing else.  Also, transistor Q502 gets really hot very fast.  I'm thinking that there still is a dead short somewhere.

[thesteve]

new ground?
can you temporarily remove the transistor

[jelloslug]

new ground?
can you temporarily remove the transistor

I ran a temporary ground wire from one of the shielding points back to the battery pack wiring until I can fix the damage around the AC adapter jack.  Yes, I can remove the transistor.

[jelloslug]

IT LIVES!  I powered it back up and used in IR thermometer to see if anything else was getting hot.  Capacitor CC901 was getting hot very quickly also so I removed it from the board and powered it back up and everything worked.  I don't know if was shorted under the cap or if the cap is bad.  The unit works without the cap so what is the function of that cap?  I also need to fix the AC power jack so if someone knows the pinout of the jack on the board that would be great.

[HercTNT]

Outstanding!! good to hear!

[jelloslug]

Outstanding!! good to hear!

I was getting worried that I had fried it some how....

[thesteve]

if the cap was heating, the cap was shorted.
CC901.......900 series is backlight i think
may be backlight control 5V

[jelloslug]

if the cap was heating, the cap was shorted.
CC901.......900 series is backlight i think
may be backlight control 5V

It's the 22uF 6V in the cap replacement chart:

[thesteve]

lol, i checked the chart before responding.
everything with a 900 number relates to backlight
500 is power supply Q506, C506, VR500 -24V/ VR501 +5V
700 series is logic/chipset ect