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Pi2Jamma Display Corruption

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sapporo46 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sapporo46 Quote  Post ReplyReply Direct Link To This Post Topic: Pi2Jamma Display Corruption
    Posted: 14 Mar 2019 at 10:48pm
But this problem first happened when everything was in the cab, connected to an arcade switching PSU.

Although as I said in my first post, it was at 5.5V - maybe feeding that through the GPIO was too much. 

As for the ATX PSU, I'd used that setup for testing several times before and that never happened.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote John Bennett Quote  Post ReplyReply Direct Link To This Post Posted: 14 Mar 2019 at 7:11am
Ah, I hadn’t realised it wasn’t a wide-range voltage input to the PI (strict 5V) and it seems you bypass protection if you power it via the GPIO header and not the USB.
So the above suggestion to change PSUs is good one.
All funny sort of things could happen if on-board regulators misbehave and there’s external circuitry.
http://www.philwip.com -sibling 'fix-off' (I’m losing by miles).
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Digimon Quote  Post ReplyReply Direct Link To This Post Posted: 14 Mar 2019 at 6:21am
the Problem is the ATX.

It has no regulation and to much power for the pi

Just try a typical arcade switching power supply..


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Post Options Post Options   Thanks (0) Thanks(0)   Quote sapporo46 Quote  Post ReplyReply Direct Link To This Post Posted: 13 Mar 2019 at 11:21pm
Yes the speaker is OK. I only took those photos yesterday... when the first Pi was damaged it was approx 7 seconds before I could cut the power. Second time round about 2 seconds, and the display corruption wasn't as bad.

It still seems to me that somehow the Pi2JAMMA had driven 5V through some of the GPIO pins, but I found this post on the Raspberry Pi forums. The OP refers to WiringPi which can apparently check the GPIO pins.

I ran it on my Pi, expecting it to report faults. But no... Confused


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Post Options Post Options   Thanks (0) Thanks(0)   Quote John Bennett Quote  Post ReplyReply Direct Link To This Post Posted: 13 Mar 2019 at 7:38am
Hmm. Well, power-wise, it’s
ATX -> JAMMA - > Pi2JAMMA -> Pi

So it’s as if the PI has pulled too much power, which isn’t the case.

The speaker is OK in the cab? I hadn’t appreciated that it’s a little power audio amp on the Pi2JAMMA (enough for an arcade speaker).

What did you do when you were getting the screenshots before to stop it smoking, or had it burnt out all it could by then?

All I can think is that there’s a bad connection somewhere or the audio amp/speaker is bad, but just early ideas.

http://www.philwip.com -sibling 'fix-off' (I’m losing by miles).
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sapporo46 Quote  Post ReplyReply Direct Link To This Post Posted: 12 Mar 2019 at 11:22pm
For info, here is how the supergun is setup.

This photo shows how the Pi2Jamma PCB connects to the Pi itself. In the cabinet, the Pi2Jamma PCB plugs into the JAMMA harness the same as on the supergun.

Here is another image of how the audio cable connects.

To answer your earlier question: according to this info, the audio cable *does* go to an amplifier.

I now have no confidence in plugging this stuff in, is the adapter board zapping the GPIO somehow? It must be, but how? Cry
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Post Options Post Options   Thanks (0) Thanks(0)   Quote John Bennett Quote  Post ReplyReply Direct Link To This Post Posted: 12 Mar 2019 at 12:43pm
I find that a bit confusing as JAMMA is amplified audio for driving big 8 ohm speakers - that’s why you’ve got amps on game boards with heatsinks on them. I’d have imagined something intended for headphones will toast itself if you stick speakers on to it.

I need to read up on the circuits to be honest though - I can’t imagine it would be like that!
http://www.philwip.com -sibling 'fix-off' (I’m losing by miles).
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sapporo46 Quote  Post ReplyReply Direct Link To This Post Posted: 12 Mar 2019 at 10:53am
I'd have to check, but it connects from the standard 3.5mm jack on the Pi and ultimately it sends the audio to whatever GPIO pins go to the JAMMA speaker connections. So it may not be related, I don't know.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote John Bennett Quote  Post ReplyReply Direct Link To This Post Posted: 12 Mar 2019 at 9:39am
What does the audio go to? An amplifier somewhere?
http://www.philwip.com -sibling 'fix-off' (I’m losing by miles).
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sapporo46 Quote  Post ReplyReply Direct Link To This Post Posted: 12 Mar 2019 at 8:16am
Certainly in terms of the GPIO connector, yes

I'm gutted, was going to buy another Pi and problem solved. The only common factor is that the damage occurs when the audio cable is plugged in. When I first tested the other Pi yesterday I didn't connect the audio cable until after it had booted.

Is this a factor somehow??

I'll upload a photo ASAP.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote John Bennett Quote  Post ReplyReply Direct Link To This Post Posted: 12 Mar 2019 at 6:20am
So it’s two trashed Pi’s?

Without knowing the circuit (any chance of an aerial photo showing all the boards and cables?), I’d be looking at the power supply area. Sounds a bit like it’s putting the ground power connection through the audio/video, although I’m not sure how that’s possible (interesting failure if so).
http://www.philwip.com -sibling 'fix-off' (I’m losing by miles).
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sapporo46 Quote  Post ReplyReply Direct Link To This Post Posted: 11 Mar 2019 at 11:10pm
An update of sorts: I borrowed a Pi and tested it out. All looked good!

I have to return it tomorrow so checked it one more time, about 30 mins ago. The audio cable smoked and the same thing has happened

I switched it off quicker this time but WTF?? I definitely didn't have it plugged in the wrong way this time, now I'm wondering if I ever did.

Bearing in mind that this was a supergun running off an ATX power supply too...

Edited by sapporo46 - 11 Mar 2019 at 11:23pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sapporo46 Quote  Post ReplyReply Direct Link To This Post Posted: 10 Mar 2019 at 9:48am
Ah, I follow you now. I'd tested the GPIO pins on the Pi2Jamma card. Electronics is not my thing
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Post Options Post Options   Thanks (0) Thanks(0)   Quote John Bennett Quote  Post ReplyReply Direct Link To This Post Posted: 09 Mar 2019 at 4:53pm
It was actually for the PI, for the GPIO driving the resistor circuit on the pi2jamma.

So you’ve tested something else using the same pins to VGA?
http://www.philwip.com -sibling 'fix-off' (I’m losing by miles).
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sapporo46 Quote  Post ReplyReply Direct Link To This Post Posted: 09 Mar 2019 at 4:08pm
Sorry John - the diode test is for the Pi2Jamma PCB, yes?

The Pi is OK - I booted it off the NOOBS for Raspberry Pi image (Raspbian OS) and it looked fine on the TV.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote John Bennett Quote  Post ReplyReply Direct Link To This Post Posted: 08 Mar 2019 at 10:03pm
You can actually do it four ways for every pin if you want to get a fuller picture:

Black to 5V, red to pin.
Black to pin, red to 0V

Red to 5V, black to pin.
Red to pin, black to 0V.

The first two are the key tests to do. I've no idea what a PI would give, but, for example 600mV is a typical reading.
However its' when one pin is radically different to the others (e.g. zero or well over a thousand) that you want to look a bit further.
Having said all this, you have got a ladder-DAC of resistors on the pins, so that might make them read differently. Maybe unplug the PI from the JAMMA thingy to test it.
http://www.philwip.com -sibling 'fix-off' (I’m losing by miles).
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sapporo46 Quote  Post ReplyReply Direct Link To This Post Posted: 08 Mar 2019 at 9:56pm
@John - I did do that test last night but wanted to double-check I was doing it properly (electronics isn't really my thing). However I did get substantial differences, I think - I'll do it again over the weekend.

If that is the case and the GPIO connector is damaged, then it's new board time I guess.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fantazia2 Quote  Post ReplyReply Direct Link To This Post Posted: 08 Mar 2019 at 6:40pm
Originally posted by sapporo46 sapporo46 wrote:

So do you think it's still possible that it's those other ones (12k and 6.8k measuring 9.02 and 5.43) that are failing?

They are only for the controls and not part of the video circuitry.

If all the controls work I wouldnt worry about them too much.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote John Bennett Quote  Post ReplyReply Direct Link To This Post Posted: 08 Mar 2019 at 4:32pm
That diode test I suggested is good for testing for blown processor I/o. Do it with the power off. Should get similar readings for the pins - if one is duff, you’ll see a big difference.
http://www.philwip.com -sibling 'fix-off' (I’m losing by miles).
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sapporo46 Quote  Post ReplyReply Direct Link To This Post Posted: 08 Mar 2019 at 4:25pm
So do you think it's still possible that it's those other ones (12k and 6.8k measuring 9.02 and 5.43) that are failing?
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