Also, try for the following voltages at these Test points:
TP500 30v
TP501 -24v
TP502 5v (ish, you will see it from 4.8 to 5v depending on factory)
The 2x Variable Resistors adjust the supply rails:
VR500 LCD Voltage Adjust (-24v)
VR501 System 5v Adjust
Check the traces+connections for both 4.7UF capacitors and the two 100UF caps near them. Make sure the same voltages are going through the via holes since these are what normally short out from old cap leakage.
That sucks.
I have a freshly recapped machine here that is fully working so I checked the voltages you have above. Most are the same, but a few are different.
- Positive side of CC503 (22uf cap) should show 24.2v
- The vias that you note are fluctuating should show 7.3v
I would test the transistors around the red backlight connector and also check and double-check the traces and vias in that area as I think your problem lies there.
The good news is if it's just the backlight, you can work around this by replacing the LCD with a modern one.
Since you confirmed no voltage on the backlight power connector I think it's safe to say it's just the backlight (it would be pretty unusual for the video to go too) - you could try shining a torch at the LCD while it's connected to see if you can make out any pixels but this is kinda tough to see in my experience.
... but just FYI, that red connector is probably for supplying power to the CCFL backlights of the LCD. IDK what voltage and current those would require with this being a handheld device, but even small CCFLs in 13-15" LCD monitors still run at 500-700V AC. So I expect the small CCFLs in this screen to still be running at relatively high voltage and probably a few mA of current or less (with total power possibly under or around a Watt.)
For this reason, don't expect to be able to measure any voltage on the red connector - not with a regular multimeter anyways. The voltage will likely be high voltage and high frequency AC. It can even damage some cheap multimeters.
That is true, CCFLs use high voltage circuits - however, the voltage on the positive terminal on that red connector should show a nominal voltage when running (4-6v - I just tested it). So you can check that. I assume the voltage is stepped up within the LCD unit itself (if you open it up, you'll see a circuit board with a high voltage warning on it).
Edit: Does the screen look like this when you turn it on?
If you can't find the problem, the system would still be a good candidate for a 3.5" LCD screen upgrade since the replacement screens have their own back lights.
Pins to lift marked(https://i.postimg.cc/hvXYyzzF/pings-marked.jpg) (https://i.postimg.cc/x8dQ01Xg/pings-marked.jpg) | Lifted and Connected (I noticed the wonky cap at this point; I had apparently "repaired" it in the past and the connection was loose. I replaced it with another later on)(https://i.postimg.cc/xTb7LmVM/lifted.jpg) (https://i.postimg.cc/KYrhBMLJ/lifted.jpg) | Grounded(https://i.postimg.cc/x8B4WfMX/lifted-and-grounded.jpg) (https://i.postimg.cc/m2t4Jhfg/lifted-and-grounded.jpg) | Grounded Alt View(https://i.postimg.cc/4dLMQb3b/lifted-and-grounded-2.jpg) (https://i.postimg.cc/9XxVLZkk/lifted-and-grounded-2.jpg) |
Done. Overhead(https://i.postimg.cc/FRs8SnhH/all-done-big.jpg) (https://i.postimg.cc/4dPZk9xm/all-done-big.jpg) | Video Board(https://i.postimg.cc/8zR00V5C/all-done-close.jpg) (https://i.postimg.cc/gkQpWdmq/all-done-close.jpg) | LCD Board w 5V mod(https://i.postimg.cc/YStscyGz/lcd-board.jpg) (https://i.postimg.cc/NjXcGV0h/lcd-board.jpg) | Pin 20 Connection(https://i.postimg.cc/cLyzhJdj/zoomed-20.jpg) (https://i.postimg.cc/wBdd1Vt1/zoomed-20.jpg) |
Pin 26 and Nearby Cap Connections(https://i.postimg.cc/jq1mWXmR/zoomed-26-and-cap.jpg) (https://i.postimg.cc/76H8VZnD/zoomed-26-and-cap.jpg) | Pin 26, 33 and 40 Connections(https://i.postimg.cc/W3HWkN95/zoomed-40-33-26.jpg) (https://i.postimg.cc/wvwKbYwN/zoomed-40-33-26.jpg) | Pin 33 and 40 Connections(https://i.postimg.cc/C11r5B4Z/zoomed-40-and-33.jpg) (https://i.postimg.cc/7hRFwM8Y/zoomed-40-and-33.jpg) | Mod Board Pin Connections(https://i.postimg.cc/yWqLLfC9/zoomed-board-pin-connects.jpg) (https://i.postimg.cc/wjLCYmWg/zoomed-board-pin-connects.jpg) |
Mod Board 5V and Cap(https://i.postimg.cc/2jPmprzd/zoomed-board-5-V-and-cap.jpg) (https://i.postimg.cc/ZYDt8ZBt/zoomed-board-5-V-and-cap.jpg) | Mod Board Resistors (https://i.postimg.cc/d3ZWRbpw/zoomed-board-resistors.jpg) (https://i.postimg.cc/J00ffYF2/zoomed-board-resistors.jpg) | LCD Board Pin 1 5V Connection(https://i.postimg.cc/3w9b3C25/zoomed-lcd-board-pin1.jpg) (https://i.postimg.cc/7YGvXc0C/zoomed-lcd-board-pin1.jpg) | LCD Board VR 5V Connection(https://i.postimg.cc/sfBy0vRD/zoomed-lcd-board-power-reg.jpg) (https://i.postimg.cc/gkfC7DHg/zoomed-lcd-board-power-reg.jpg) |
As you can see, all 4 signal pins should be connected together after passing through their resistors. On your board they are not doing that. Also, 3 of your signal pins(20,26,33) are going to a spot with no transistor installed.
(https://i.postimg.cc/Z5hstT3W/pcegt-pcb.jpg) (https://i.postimg.cc/JzWXPSLc/pcegt-pcb.jpg) | (https://i.postimg.cc/qMKD5ttf/pcegt-composite-pcb-connections.jpg) (https://i.postimg.cc/X75FK4TY/pcegt-composite-pcb-connections.jpg) |
I've never seen a HU6260 chip produce absolute no video at all. If bad, the colors or graphics are generally just all messed up.
I'm not saying it couldn't happen where the chip is dead altogether and won't produce any picture whatsoever. I've just never come across one that has done that.
The 75ohm resistor is just to lower the Brightness slightly but I think that's mainly just needed for other transistors that amp the signal more. I've noticed that the 8050 transistor has the correct brightness without one and will be too dark with one.
I have gotten all of the parts in for the AV boards, so I'm hoping to tackle this project again this weekend. I have 2 options for my Composite AV Board, I can build one with your (Keith's) schematic on prototyping board, and/or I can populate one of the boards I ordered from OshPark.
The boards from OshPark include an additional AV hookup on the board for doing an AV Out mod. Does anyone know of any guides on doing AV Out? I'd love to know how to repurpose the com port for this, if that's possible? I've tried searching these forums and the internet in general, but haven't been able to find any guides on this. :'(
(https://i.postimg.cc/mkTgKBXN/HOORAY.jpg) | (https://i.postimg.cc/d1P1m8Gf/game-close.jpg) |
(https://i.postimg.cc/gktqNNsr/Keith.jpg) (https://postimg.cc/N9zHKdsQ) | (https://i.postimg.cc/Jzy3gZYx/Ninja.jpg) (https://postimg.cc/Cd98YrrN) |