Help with repair of Turbo Express

jelloslug · 10/03/2012, 09:33 PM

I working on a TE that needed a full cap replacement. Everything was going well, all the caps went in OK and all the standard issues were repaired. I closed it back up, powered it up and the first thing that happened was that the brightness wheel no longer worked but the brightness was still OK. Very shortly afterward the backlight started flickering and the unit shut down. It would power back for for no more than half a second and then it was all dead. The 1 amp fuse was blown so I check the board over for shorts and replaced the fuse. With the fuse replaced the backlight would come on and that was it. The new fuse does not blow but nothing else works. And pointers on where to looks would be great.

Keith Courage · 10/03/2012, 09:39 PM

Try using new batteries or an ac adapter. Typically when the contrast wheel doesn't work it's because the batteries are low.

jelloslug · 10/03/2012, 10:14 PM

The batteries are not it, I put a fresh set in with no change. Everything was working fine until I closed it up then everything stopped working right.

thesteve · 10/03/2012, 10:46 PM

check the 5V regulator for system function, and the 24V supply for the brightness issue.
the 5V can be found on most caps.
the 24V on 1 cap and 1 pin on the display

jelloslug · 10/03/2012, 11:07 PM

Quote from: thesteve on 10/03/2012, 10:46 PMcheck the 5V regulator for system function, and the 24V supply for the brightness issue.
the 5V can be found on most caps.
the 24V on 1 cap and 1 pin on the display

I have 5V at every cap but I could not find 24V anywhere.

thesteve · 10/03/2012, 11:20 PM

controller must be connected for 24
pin3 of the screen is -24V

turbokon · 10/03/2012, 11:24 PM

You have a short somewhere, also double check polarity.

turbokon · 10/03/2012, 11:32 PM

Also check to see if the controller ribbons are connected probably.

HercTNT · 10/03/2012, 11:35 PM

Hoping for another happy ending, were pulling for you jello

jelloslug · 10/03/2012, 11:43 PM

Polarity is good and the controller ribbon is fine. I'm not getting 24V at the video connector and the system still appears to be dead.

jelloslug · 10/03/2012, 11:57 PM

I went over both sides of the board looking for dead shorts and I could not find anything. What caps have to be replaced when a unit usually won't power on?

thesteve · 10/04/2012, 12:01 AM

any sound?

jelloslug · 10/04/2012, 12:17 AM

Quote from: thesteve on 10/04/2012, 12:01 AMany sound?

Nothing. Not from the speaker or the headphone jack, not even a pop when you turn the system on. Both the speaker and the headphone jack were working properly before the problems started.

Also, just to clarify, when the system failed for the last time the game started and then just froze up after about a second, then the next few times when you turned it on you got just the backlight and then lastly nothing happened. I had to replace the AC jack so I'm wondering if I might have damaged some of the components under the gray glue on the back side of the board near where the pins on the AC jack poke through.

thesteve · 10/04/2012, 01:04 AM

the chipset and sound should work without the 24, its for the screen only.
the pop is from the amp, not the chipset.
what caps did you use?
and please check them for voltage (meter across cap power on)

jelloslug · 10/04/2012, 08:06 AM

Quote from: thesteve on 10/04/2012, 01:04 AMthe chipset and sound should work without the 24, its for the screen only.
the pop is from the amp, not the chipset.
what caps did you use?
and please check them for voltage (meter across cap power on)

The caps were a kit I bought specifically for the TE. There is 5V on both sides of all the caps.

thesteve · 10/04/2012, 03:00 PM

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

jelloslug · 10/04/2012, 04:47 PM

Quote from: thesteve on 10/04/2012, 03:00 PMboth 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 · 10/04/2012, 04:54 PM

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

jelloslug · 10/04/2012, 05:00 PM

Quote from: thesteve on 10/04/2012, 04:54 PMlol
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 · 10/04/2012, 05:40 PM

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 · 10/04/2012, 06:53 PM

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 · 10/04/2012, 07:55 PM

Quote from: thesteve on 10/04/2012, 06:53 PMyes 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 · 10/04/2012, 08:07 PM

new ground?
can you temporarily remove the transistor

jelloslug · 10/04/2012, 08:12 PM

Quote from: thesteve on 10/04/2012, 08:07 PMnew 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 · 10/04/2012, 08:42 PM

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 · 10/04/2012, 10:12 PM

Outstanding!! good to hear!

jelloslug · 10/04/2012, 10:13 PM

Quote from: HercTNT on 10/04/2012, 10:12 PMOutstanding!! good to hear!

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

thesteve · 10/04/2012, 10:41 PM

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

jelloslug · 10/04/2012, 10:59 PM

Quote from: thesteve on 10/04/2012, 10:41 PMif 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 · 10/04/2012, 11:44 PM

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

jelloslug · 10/05/2012, 08:13 AM

Quote from: thesteve on 10/04/2012, 11:44 PMlol, 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

Cool. How about the pin out for the board side of the AC adaptor jack? The traces are really bad in that area on mine so I can't really see how to fix that at this point.

turbokon · 10/05/2012, 10:47 AM

One time I had a TE that was acting up like yours. I smell something burning. I opened it up , fired it on and saw smoke coming from the transistor near the cap you mentioned. I had a short across that cap. Sure enough I saw a piece of solder wedged between two contacts of the connector that the controller pcb connects to. I remove the solder piece and that cap no longer shorted. Funny thing the fuse didn't blow and it works just fine after that.

Xenogears · 11/01/2017, 04:22 PM

My TE Video has died. I changed the Caps as I had the Dark Screen issue. Now everything is unchanged after a complete Recap. The Unit works, Sound is there but the Backlight is only very dark, Constrast Adjustment does nothing. I decided to create a "Check your GT Testpoint-Values" Spreadsheet. Here are my values - Excel-Sheet on Fileupload:

GTCHECK.xlsx

The Chart is not complete yet, so please feel invited to add working Values and fault Values. Maybe we could create a Quick-Test System: If TP 50X shows that Value, Part no XXX is broken/trace is dead.

I need to find out, why -24V are missing and why Q500 / CC501 /L500 are getting hot...