PCE GT Lithium Battery Mod Guide

[userofapples]

i got it working but it was way too bright even though i tried to adjust the brightness dial down.  after a certain point the screen just turned off, at the lowest setting when working the type of game that i was trying to select was not visible.  not worth the effort for my system at least.

[lamb2k]

This is great. Where did you find the resistor? I'm having trouble chasing down the exact part here in the US.

[MasterofBiscuits]

This is great. Where did you find the resistor? I'm having trouble chasing down the exact part here in the US.

If you mean the 1.8mohm resistor for the Powerboost board, I usually buy my components from Farnell, although there are lots of similar online stores (RS Online, Mouser etc).

https://www.newark.com/c/passive-components/resistors-fixed-value/chip-smd-resistors?resistor-case-package=0805-2012-metric-&resistance=1.8mohm

Any of these should be fine.

[kattare]

Really cool mod. Could you do this and still use the original adapter instead of USB power?

IE, split the original circuit at the regulator output. Route the regulator output into the 1000c 5v input. Then route the 1000c 5v output to the board where the regulator used to feed it?

Is the OEM adapter's 700mA too low to charge the batteries & run the system at the same time?

[lamb2k]

His second reply/post has a schematic for using the original adapter port for charging.

[kattare]

His second reply/post has a schematic for using the original adapter port for charging.

He's still using a USB power supply - just adding a barrel plug.

For charging I'm using a USB cable that has changeable barrel ports: https://www.amazon.co.uk/gp/product/B07GTKBVKN/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

I asked if you could use the original AC adapter. The USB adapter is 5v whereas the original adapter is 7v, so you'd need to pass through the regulator before feeding the charging board.

My concern would be the current draw when charging and playing. Not sure the original adapter could supply both at once.

[MasterofBiscuits]

Really cool mod. Could you do this and still use the original adapter instead of USB power?

IE, split the original circuit at the regulator output. Route the regulator output into the 1000c 5v input. Then route the 1000c 5v output to the board where the regulator used to feed it?

Is the OEM adapter's 700mA too low to charge the batteries & run the system at the same time?

Hmm, techically you could since it would be a regulated 5v coming out of the original regulator, but as you suggested the 700ma is too low to power when playing & charging, which needs around 1.3a when the battery is at its lowest, and I recommend at least a 1.5a USB source.

The real question is why would you want to when there are so many better options. Nobody should be using the original unregulated PSUs from the 90s, they are old and inefficient. Just get USB cable with a barrel jack and you're done.

[kattare]

Hmm, techically you could since it would be a regulated 5v coming out of the original regulator, but as you suggested the 700ma is too low to power when playing & charging, which needs around 1.3a when the battery is at its lowest, and I recommend at least a 1.5a USB source.

Bummer

The real question is why would you want to when there are so many better options. Nobody should be using the original unregulated PSUs from the 90s, they are old and inefficient. Just get USB cable with a barrel jack and you're done.

Agreed that the old supplies are inefficient, but I've found newer switching supplies to be pretty hit or miss with regard to how clean the power is.  At one point I went through all my gear swapping in switching supplies so I could leave more stuff plugged in and not worry about it - but after a while realized that for several systems it had introduced static or rolling distortion in the picture. I went back to my old setup with a remote-based master on/off switch on the power strip where the transformers are plugged in.

I have found that not all switching supplies are like that - but it's easier (and cheaper, since I already have them) to just use the OG supplies than it is to iterate through brands trying to find good switching supplies.

Interference on the express probably wouldn't be an issue but USB supplies have the same issues - very hit or miss with specs and quality - look no further than the number of bricked TG/PC Engine mini's: https://www.reddit.com/r/TurboGrafx/comments/gojsub/my_second_pc_engine_minis_usb_ports_have_stopped/

Cheers

[lamb2k]

Thanks for this Master of Biscuits.

A few questions:
1) Where exactly does the wire for USB go for the scenario of aftermarket LCD with stock charging port?
2) Do you have any tips for removing Q502's resistor without damaging the PCB? Same for removing the resistor on the Adafruit. Th

[MasterofBiscuits]

Thanks for this Master of Biscuits.

A few questions:
1) Where exactly does the wire for USB go for the scenario of aftermarket LCD with stock charging port?
2) Do you have any tips for removing Q502's resistor without damaging the PCB? Same for removing the resistor on the Adafruit. Th

1) Not sure I understand the question, could you explain a bit more about what you're trying to do? Aftermarket LCDs can be powered from the Powerboost board, the USB input for the Powerboost should go to wherever your USB power is attached to the console.
2) Q502 can easily be removed with a soldering iron, just add flux and a bit of extra solder to the large end, hold for a few seconds, then put your iron across the pins on the other side. Just keep getting heat on there and it will just slide off in no time.
The resistor on the Powerboost is a bit trickier, ideally you need hot air. If you don't have one, add some leaded solder on both sides and use a large iron tip to heat both sides at once and push it off. Shouldn't be too difficult, the hardest part is actually getting it off as the board is so crowded.

[MLA]

Just need to remove Q502 and wire the 5v to the large pad, hook up the USB charge input to the rear pin of the dc adapter (I wired it around the board, but you can just remove the grey silicone and connect to the pin) and the ground goes on TP510.

Very nice work MasterofBiscuits 

I am modding a PC Engine GT and have a couple of questions if you have a moment to spare and help out:

1) I have tried wiring the stock brightness wheel to the LCDDRV board as described in this thread, but it did not work very well, and in the end it fried the fuse on the GT motherboard. I was going to give up on this part of the mod, but just noticed in your photo above that you are using some resistors to wire the stock brightness wheel? does this work better, would you have any info to share? I do not want to risk that the person for whom I am modding the GT ends up frying the fuse again, so I hesitate to hook up the stock brightness wheel if it is not reliable/safe.

2) for the LEDs could you please share what values you are using for the current limiting resistors?  Also, I suppose that you drilled a little hole on the shell for the second red/ orange LED?

3) you mention that you use a USB cable for charging. So charging at 5V? The original charger for the GT is 7.5V so I suppose it is out of question to use the original charger at the risk of frying the Adafruit Powerboost?

Thanks in advance for the advice/answers! 

[MasterofBiscuits]

Just need to remove Q502 and wire the 5v to the large pad, hook up the USB charge input to the rear pin of the dc adapter (I wired it around the board, but you can just remove the grey silicone and connect to the pin) and the ground goes on TP510.

Very nice work MasterofBiscuits 

I am modding a PC Engine GT and have a couple of questions if you have a moment to spare and help out:

1) I have tried wiring the stock brightness wheel to the LCDDRV board as described in this thread, but it did not work very well, and in the end it fried the fuse on the GT motherboard. I was going to give up on this part of the mod, but just noticed in your photo above that you are using some resistors to wire the stock brightness wheel? does this work better, would you have any info to share? I do not want to risk that the person for whom I am modding the GT ends up frying the fuse again, so I hesitate to hook up the stock brightness wheel if it is not reliable/safe.

2) for the LEDs could you please share what values you are using for the current limiting resistors?  Also, I suppose that you drilled a little hole on the shell for the second red/ orange LED?

3) you mention that you use a USB cable for charging. So charging at 5V? The original charger for the GT is 7.5V so I suppose it is out of question to use the original charger at the risk of frying the Adafruit Powerboost?

Thanks in advance for the advice/answers! 

1)IIRC that pic shows a composite modded machine, so different wiring than the LCDDRV. I tend use the RGBDRV boards so don't have much experience of the LCDDRV, I've only done a couple of them.
2)A 1k resistor on each should be fine, that's what I usually use. I drill a 3mm hole in the shell, measure 1cm away from the centre of the power jack hole. I fit one of these from the inside  with the end snipped off: https://uk.farnell.com/bivar/plp1-125-f/light-pipe-single-3-2mm-panel/dp/2748704
3) Yes charging at 5v, that's what the adafruit board needs. You cannot use the original power brick (why would you, when you can use USB! )