MSXmakers support

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By RayneX

Rookie (32)

RayneX's picture

23-06-2022, 16:01

Thank you for the detailed description, but unfortunately your first test failed on my switch. In the OFF position, there is no continuity between any terminal. When I switch it the ON position, 2 of the Terminals do have Continuity. Here's the switch I'm using. Maybe I got the wrong one?
https://www.amazon.com/dp/B07QH5NSCJ?psc=1&ref=ppx_yo2ov_dt_...

By msxmakers

Champion (453)

msxmakers's picture

23-06-2022, 16:07

RayneX wrote:

U2 IC - Pin 6 (PPI_CS) - 4.6V (my friend said this should be 0V based on his understanding of the quick reading of the schematics)
U2 IC - Pin 6 (PPI_CS) - No frequency reading on the scope.
U12 - Pin 14 (PPI_CS) - Same as U2 results. No frequency reading on scope
My friend is asking what actually activates the PPI_CS. Do you know?
Does this help you narrow down where the issue could be?
Does it seem to narrow it down that the 82c55 could be bad?

PPI_CS is the chip select signal for the PPI chip, the PPI chip is the 82c55, so if you never put it low (zero) it's never active. this chips is in charge to control the slots, by the end the ROM&RAM access.
It's controled by the "chip select" gal.
So, you can have a bad solder at U12. Input or output.
you can also have a mistake on the GAL program, as easy as take it out of the omega and simulate it inputs to get the right output (if works).
/PPICS = /IORQ * M1 * A7 * /A6 * A5 * /A4 * A3 * /A2
the pin definition say:
WR IORQ A7 A6 A5 A4 A3 A2 A0 GND
M1 PRTDATWR PRTCMDCS PPICS PAGECS RTCCS RTCADWR VDPCS PSGCS VCC
so, if it's programed properly, you can put those pins
2, 11, 3, 6, 5, 4, 3 & 2.
that way
0, 1, 1, 0, 1, 0, 1 & 0
... and you should obtain "0" at pin #14
Don't forget to put +5v at vcc and 0v at gnd.
If that works as expected we'll follow looking for.

By msxmakers

Champion (453)

msxmakers's picture

23-06-2022, 16:12

ahmsx wrote:

Hi,
I did the wiring in the following way.
I put the switch in the OFF position and using a multimeter checked which of the non-middle terminal legs of the switch had continuity with the middle terminal leg of the switch. That terminal leg is the OFF terminal leg, and the remaining non-middle terminal is the ON terminal leg.
Then I wired the switch middle terminal leg to the terminal block pin number 2 (the middle pin of the terminal block), the switch OFF terminal leg to the terminal block pin number 1 (the terminal pin in the terminal block which is closer to the discharging resistor R1) and finally the switch ON terminal leg to the terminal block pin number 3 (the remaining pin on the terminal block).
This is the board before the assembly and cabling.

And this is the board after (a quick and careless...) assembly and cabling.

Such a good job :P

By RayneX

Rookie (32)

RayneX's picture

23-06-2022, 16:18

msxmakers wrote:
RayneX wrote:

U2 IC - Pin 6 (PPI_CS) - 4.6V (my friend said this should be 0V based on his understanding of the quick reading of the schematics)
U2 IC - Pin 6 (PPI_CS) - No frequency reading on the scope.
U12 - Pin 14 (PPI_CS) - Same as U2 results. No frequency reading on scope
My friend is asking what actually activates the PPI_CS. Do you know?
Does this help you narrow down where the issue could be?
Does it seem to narrow it down that the 82c55 could be bad?

PPI_CS is the chip select signal for the PPI chip, the PPI chip is the 82c55, so if you never put it low (zero) it's never active. this chips is in charge to control the slots, by the end the ROM&RAM access.
It's controled by the "chip select" gal.
So, you can have a bad solder at U12. Input or output.
you can also have a mistake on the GAL program, as easy as take it out of the omega and simulate it inputs to get the right output (if works).
/PPICS = /IORQ * M1 * A7 * /A6 * A5 * /A4 * A3 * /A2
the pin definition say:
WR IORQ A7 A6 A5 A4 A3 A2 A0 GND
M1 PRTDATWR PRTCMDCS PPICS PAGECS RTCCS RTCADWR VDPCS PSGCS VCC
so, if it's programed properly, you can put those pins
2, 11, 3, 6, 5, 4, 3 & 2.
that way
0, 1, 1, 0, 1, 0, 1 & 0
... and you should obtain "0" at pin #14
Don't forget to put +5v at vcc and 0v at gnd.
If that works as expected we'll follow looking for.

Thank you for the reply. I resolved this yesterday. I replaced the 82c55 with the exact one from the BOM and it booted up like a champ. Got to play a game, test the keyboard (keyboard had a bad switch and a bad LED, so I swapped those out), and everything seems to be working so far. The mystery is finally solved.

By msxmakers

Champion (453)

msxmakers's picture

23-06-2022, 16:21

RayneX wrote:

Omega MSX Build
Here are semi-high resolution shots of my build. (Ignore the masking tape on the GAL chips. I left it on by mistake on the Chip Select; it is programmed correctly for Chip Select). My friend who finally was able to start the Smoke tests also has the exact same error at Smoke Test 4.

thanks trying to supply pictures but you will need to add light, about 10 the current you are. also you should clean the solder side, please, take isopropil alcohol, some kitchen paper and an old teethbrush and fight with it until it glow.
We won't be able to see a problem below the flux, neither you.
I don't like soldering legs in diagonal way but it's your choice.
:hannibal:

By msxmakers

Champion (453)

msxmakers's picture

23-06-2022, 16:28

this is another way to mount the mini-dc board, that way it does not touch with floppy drive or any other device because we can put it any place. As you can see its not pluged on the motherboard:

and still another way, with the power switch in the rear:

By ahmsx

Supporter (8)

ahmsx's picture

23-06-2022, 18:01

Hi,

It looks like your switch is a single pole single throw (SPST) switch with a led/light, which has 3 legs but works differently: the gold leg is usually the GND leg for the led, the other two silver legs are usually the "normal" legs of a switch (you connect one leg to VCC and the other leg to the load). So using a multimeter you will just get continuity when testing the two silver legs with the switch ON (just as you noticed).

The DC Adaptor board expects AFAIK a SPDT (single pole, dual throw) switch in order to be able to use the discharge circuit when off.

Cheers.

By RayneX

Rookie (32)

RayneX's picture

23-06-2022, 19:06

ahmsx wrote:

Hi,

It looks like your switch is a single pole single throw (SPST) switch with a led/light, which has 3 legs but works differently: the gold leg is usually the GND leg for the led, the other two silver legs are usually the "normal" legs of a switch (you connect one leg to VCC and the other leg to the load). So using a multimeter you will just get continuity when testing the two silver legs with the switch ON (just as you noticed).

The DC Adaptor board expects AFAIK a SPDT (single pole, dual throw) switch in order to be able to use the discharge circuit when off.

Cheers.

Yep, I did order the wrong ones then. Doesn't seem to be a common switch as I had to order from Digikey just now. I avoid Aliexpress when I can due to long shipping times. If time wasn't so much a factor, I'd just order from the links. Thanks for the help. Smile

By RayneX

Rookie (32)

RayneX's picture

24-06-2022, 00:53

Was the original acrylic case modified in any way to take into consideration the mounting of the DC12V adapter? I'm seeing major issues right now and I'm not quite there yet with assembling the case. Is there enough room to mount that board somewhere? I don't think it's possible cause the barrel plug opening in the acrylic is set to the original location.

By RayneX

Rookie (32)

RayneX's picture

24-06-2022, 03:25

msxmakers wrote:

this is another way to mount the mini-dc board, that way it does not touch with floppy drive or any other device because we can put it any place. As you can see its not pluged on the motherboard:

and still another way, with the power switch in the rear:

I'm pretty sure I'm going to have to do something like this in the original acrylic case. I just have to find a spot for that and the up converter. There's just no way else to mount it. My bracket is only useful in certain cases then. Dang it, it works really well too. Just tested its functionality and plugging it in and unplugging it was completely solid.

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