piscope looks interesting, too bad it can only sample at max of 100kbps.....
I'm not sure about the rate but I'll try to determine it somehow.
Got a tip for us?
Let us know
Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
iMac G3 mod - Video Connector
- Thread starter ym58
- Start date
- Sort by reaction score
I'm not sure about the rate but I'll try to determine it somehow.
I figured out how to turn on my second iMac CRT without the logic board. I think this method is the most generic
way of turning on the CRT and can be applied to my other iMac. Have to connect PFW + LP + 5V trickle and leave connected. Send the second init script and voila!
Here is a video
way of turning on the CRT and can be applied to my other iMac. Have to connect PFW + LP + 5V trickle and leave connected. Send the second init script and voila!
Here is a video
Oh man, I love this! I wonder if you could run an i9 9900T off the 150 watt power supply!
I moved my tray loader mod write up here if anyone is interested: http://whatdoyouguyswannado.com/Zotac_Powered_Grape_iMac_revD/
I moved my tray loader mod write up here if anyone is interested: http://whatdoyouguyswannado.com/Zotac_Powered_Grape_iMac_revD/
You could use a pick power supply to power a small atx board. They need very little space
[automerge]1582146106[/automerge]
Something like this would work http://www.mini-box.com/picoPSU-160-XT
I was actually looking at those the other day and they seem like they would do the job but
they still require a 12v supply.
If the down converter board really is 150W , we could use that and it already mounts
to the chassis. I actually wired it to both the J20 connector and the J22 connector the other night
and it worked really well. It turns on when the CRT came on and turns off when it was
powered off.
What do you think?
If you use the down converter board thats one less thing you need to remove from the chassis and we know it works for the CRT. On the other hand the Pico PSU is really small and would give more space for installing an atx system. Also easier to find and replace a Pico PSU than a now 21 year old PSU that is no longer manufactured and is only available second hand.
I'd say an alternate power supply is the better option if you have the budget
I'd say an alternate power supply is the better option if you have the budget
That's a good point so then we would need to rectify the 24V AC coming from J22 that powers the
down converter board and then step it down to 12V DC in order to feed the pico PSU. I'm sure
there's something out there that already does that and it would have to be able to provide around 14 amps.
Just have to do some searching....
Also, now that I've rung out the dual headphone board, I think I have enough info on the chassis connectors that I can start making schematics to take advantage of things.
I want to be able to use the following.
1 - speakers
2 - power switch & LED
3 - mic
4 - dual headphone board
I want to embed a couple of atmega328pu chips, one powered by the trickle voltage supplied by J20
and the other powered by the voltage supplied via the VGA connector when a computer plugs into it.
I haven't decided if I want to turn the G3 into an external monitor where the VGA connector comes out of the back where
the current VGA connector is or embed a computer like a raspberry pi inside of it.
If I use it as an external monitor I would have to route the mic , speaker,dual headphone jacks and power button connectors to the side of the case.
If you anyone has any ideas please let me know and I'll try an incorporate them(always trying to make it inexpensive of coarse).
down converter board and then step it down to 12V DC in order to feed the pico PSU. I'm sure
there's something out there that already does that and it would have to be able to provide around 14 amps.
Just have to do some searching....
Also, now that I've rung out the dual headphone board, I think I have enough info on the chassis connectors that I can start making schematics to take advantage of things.
I want to be able to use the following.
1 - speakers
2 - power switch & LED
3 - mic
4 - dual headphone board
I want to embed a couple of atmega328pu chips, one powered by the trickle voltage supplied by J20
and the other powered by the voltage supplied via the VGA connector when a computer plugs into it.
I haven't decided if I want to turn the G3 into an external monitor where the VGA connector comes out of the back where
the current VGA connector is or embed a computer like a raspberry pi inside of it.
If I use it as an external monitor I would have to route the mic , speaker,dual headphone jacks and power button connectors to the side of the case.
If you anyone has any ideas please let me know and I'll try an incorporate them(always trying to make it inexpensive of coarse).
Using the trickle voltage provided by the J20 connector to power an arduino nano to detect button presses
and turn on the CRT and the power-LED.
Here is a video.
and turn on the CRT and the power-LED.
Here is a video.
I have a really cheap DIY audio amplifier project that needs soldering together... I bet I could use that to run the speakers. Like £5 on eBay.
I would work on a single board that allowed it to work independently as a monitor. Would you be able to wire up the edid and init arduinos to a single prototyping board with the power switch? From there we can simplify the board down to a couple of headers and a VGA female port. That would reduce the necessity of cutting wires altogether and you could just plug a couple of cables into the base of the iMac and into the board then plug your VGA cable into the female connector. If we get a diagram together for that we can have a couple of prototype pcbs put together. Maybe later try to add or create an audio DAC that can be added to the board and wire in the speakers.
Once that's done we have a single board that can be connected to any iMac and you can plug any tiny pc into the case.
If you wanted to add a small pc you would get a Pico PSU and find a way to power the CRT and mobo from that instead of the PAV so we aren't running a modern pc on an old power board (age issues, inconsistent power issues, energy inefficiency)
I would work on a single board that allowed it to work independently as a monitor. Would you be able to wire up the edid and init arduinos to a single prototyping board with the power switch? From there we can simplify the board down to a couple of headers and a VGA female port. That would reduce the necessity of cutting wires altogether and you could just plug a couple of cables into the base of the iMac and into the board then plug your VGA cable into the female connector. If we get a diagram together for that we can have a couple of prototype pcbs put together. Maybe later try to add or create an audio DAC that can be added to the board and wire in the speakers.
Once that's done we have a single board that can be connected to any iMac and you can plug any tiny pc into the case.
If you wanted to add a small pc you would get a Pico PSU and find a way to power the CRT and mobo from that instead of the PAV so we aren't running a modern pc on an old power board (age issues, inconsistent power issues, energy inefficiency)
Actually and fortunately, the analog board and the CRT don't depend on the down converter board, you can use the CRT without it. J22 provides the 24 VAC that powers the down converter board and J20 has a control line that turns it on and
off(I think). All we have to do is power something like the down converter board from J22.
Something like the one in the link below but capable of providing more current.
AC 24V to DC 12V Power Supply Converter
Wire it like
PAV board
[automerge]1582256581[/automerge]
I've played around with my second G3 and I think the sequence I'm using now will work for your G3.
1 - connect 5V TRICKLE to PFW and LPIACT and keep it connected.
2 - boot the pi 4 using "init_ivad_2.py" instead of "init_ivad.py" (remember to make it executable)
Turning on the CRT
Here's a video of it working with other G3
Last edited:
So what kind of power and draw does the CRT need to work? If i were to power the CRT from the wall socket in my house it outputs 240v AC i would need to convert that to 12v DC or 24v AC? and then supply power through Pins 23 and 24 or 25 and 26? and this will power the CRT without using any of the internal power components? What kind of Amperage or or wattage would be required?
I will be able to put some time into getting it working on my pi tomorrow and update you, once ive got that i will look at driving the speakers but i think this will be relatively easy to do.
Here's how things get the power they need(at least on my models)
1 - 120 VAC (240 VAC in your case) from the wall socket directly into the back of the iMac. This goes straight into the analog board.
2 - The analog board(top board) converts the input voltage to power the CRT and provides 24VAC via the J22 connector
and provides the 5V trickle voltage via the J20 connector.
3 - When the logic board(bottom board) is plugged in, the 24VAC is routed through one side of the logic board via the J22 connector to the other side of the logic board and into the down converter board via the ATX style connector.
4 - The down converter board converts the 24VAC to the typical mother board voltages 12 VDC , 5 VDC and 3.3 VDC
and then sends it right back into the logic board via the same ATX style connector in order to power the logic board.
So pins 23 through 26 provide the 24VAC to the logic board and it's just routed through don to the down-converter board.
5 - The analog board provides the 5V trickle voltage via the J20 connector to power a micro controller on the logic board.
The micro controller monitors button presses, sends the initialization sequence to the IVAD board, and turns the CRT on with PFW and LP . It does this via the J20 connector right back to the analog board. This is the basic functionality I'm
trying to implement with an arduino micro controller.
This seems like a really odd design to me and it took me a while to wrap my head around it.
It's what we have.........
Can't wait to see your progress!
I just finished reassembling my 1st iMac after replacing the bulging capacitor and tested it with
the initialization script captured from my second iMac.
The 2nd initialization script although different, works with my original iMac so I've decided to replace the 1st init sequence
with the second one on my repo. No sense in keeping two different ones if one works with them both.
Link to repository
the initialization script captured from my second iMac.
The 2nd initialization script although different, works with my original iMac so I've decided to replace the 1st init sequence
with the second one on my repo. No sense in keeping two different ones if one works with them both.
Link to repository
playing around with the pcb layout. here is a pcb for the j20 connector.
I still need to add some stuff including pins for the on switch.
I still need to add some stuff including pins for the on switch.
Rockyhill, just wanted to say a massive thank you for documenting all those pinouts. I'm currently in the process of doing a complete conversion (similar to this one but different mounting locations) on a slot-loading G3, and those pinouts on your github repo will be a huge help to get everything hooked up.
Back on topic, I also have a low end tray loading and a low-end slot loading G3 that are begging for a PieMac/NUC mod. If you end up doing a batch of these conversion PCBs, I'd love to buy a couple and test them out.
>Yes, those are the arduino chips but might remove one for rev 1.
Is it possible to run both the IVAD board init and edid simulation off a single ATMEGA?
Back on topic, I also have a low end tray loading and a low-end slot loading G3 that are begging for a PieMac/NUC mod. If you end up doing a batch of these conversion PCBs, I'd love to buy a couple and test them out.
>Yes, those are the arduino chips but might remove one for rev 1.
Is it possible to run both the IVAD board init and edid simulation off a single ATMEGA?
Last edited:
Thanks, I was looking at your project on github, very nice.
I can't wait to see it finished.
As far as the PCB's go, I'm sure we could come up with something.
I'm also planning on publishing the PCB gerbers on my repo so it might actually be
cheaper if you ordered them yourself from some place like oshpark.com but we'll see
what the best option is later on I guess.
I've tried to get everything working with just one Arduino but I have had mixed results. Sometimes
it works great, sometimes it kind of works and sometimes it doesn't all. I might have to find a chip
that has two i2c ports and is easy to install.
Thank you for all your work on this, Rockyhill. Haven't had much time to work on this as of late, but tonight I tried it with the updated configurations and got the same results. Increasingly convinced the CRT no longer works, so I will put the logic board back in this week and report back.
I2C is a bus so the device at the remote end needs an address in order to run them individually on a single chip. Are you running it in sequence or with interupts?
Good find and we could definitely go that route but I sort of wanted to make the boards using a micro controller with
supported open source tools so that anyone can program them without having to buy a compiler.
Also the packaging on that chip would make it extremely difficult to solder onto a board.
That said, Microchip does have many chips available in DIP package form and they do offer a free limited C compiler for some of these.
The same goes for the STM chip on the arduino DUE which also has dual i2c ports, the packaging would make it extremely difficult to solder.
There are smaller chips with i2c pins in the atmel family of mcu's but the atmega328p is the most popular one and chances
are that most arduino enthusiasts have the arduino uno which means they can program the chip right one the arduino uno,
pop it out, and place it on the iMac board.
I know the board will look clunky with two atmega328p's but I think it will make it easier to work with in the long run.
I could make the whole thing with surface mount components making it smaller and nice looking but then that would really
make it extremely difficult for most people to assemble.
[automerge]1582815732[/automerge]
Well, I've tried it several ways, trying as both slave and master on the same bus and played with a couple of libraries that create a software i2c bus that can be used on almost any two pins.
The latter is the configuration I've had the best results with but it just isn't reliable. Sometimes it works and sometimes it doesn't.
I do do this at night when I'm tired so I could be missing something.
Last edited:
I agree with you here this should be simple to build. Get the board printed, add the connectors, add the resistors and chips and be ready to rock.
-Audio
I looked at my mini solder project amp and found it needs a power supply i dont own so i went onto the bay and found a really small 5v 3w stereo amp and should arrive monday/tuesday (Stupid China). Looking at the board pinouts i should be able to power it from J7 3 and 4 and use J22 4,9 and 10 for the audio input H1 to test the audio. you can use the front 3.5mm mic port for input direct to speakers and have a really cool looking Jukebox with lovely harman kardon sound.
H1 and H2 can be wired to the analog audio port on a Mobo if you go that route. then you would need either a secondary internal audio header to connect the amp to or a 3.5mm from the motherboard external IO back into the amp inside the case but thats ugly. The RPi option is to get an HDMI to VGA + Audio adapter and hide it inside the case or just use the audio out and wire to the amp.
I cant be much help with the screen at this point other than testing and reporting back to you because you're pretty much in the refining stage. But i can and will get the audio sorted and work a way to integrate this with your board