1088XEL Atari ITX Motherboard DIY Builders Thread

[Lavalamp]

Finally got the 1088XEL assembled but it turns out my 5V Adapter from Digikey was DOA, I'll source one locally, does the 1088XEL require 2A? I cant seem locate a match. I tried a 5v 1A I have, but I get no power on LED, just flickering LED son the USB/SIO board. :/ Thanks in advance.

[+MacRorie]

Finally got the 1088XEL assembled but it turns out my 5V Adapter from Digikey was DOA, I'll source one locally, does the 1088XEL require 2A? I cant seem locate a match. I tried a 5v 1A I have, but I get no power on LED, just flickering LED son the USB/SIO board. :/ Thanks in advance.

 

 

Be very careful, 5v DC power supplies other than the one specified have shown to get some odd results.

[Lavalamp]

 

 

Be very careful, 5v DC power supplies other than the one specified have shown to get some odd results.

 

I understand a 2A USB Power Adapter will work?

[+MacRorie]

 

I understand a 2A USB Power Adapter will work?

 

 

It probably will. I am just saying that even power supplies that are of the same specifications as the one in the BOM have shown to be a little odd in its results. quite a few were tried.

[+mytek]

I understand a 2A USB Power Adapter will work?

No most USB adapters are really more of a charger, than meant to act as a standalone PSU, meaning that they depend upon the battery to smooth things out.

 

What MacRorie is referring to was associated with the early beta version of the 1088XEL where there were problems with some standalone PSUs, but that got remedied by improving the DC filtering on board, so most any 2 Amp or greater supply with a center positive and the correct size plug should work fine now.

[Lavalamp]

No most USB adapters are really more of a charger, than meant to act as a standalone PSU, meaning that they depend upon the battery to smooth things out.

 

What MacRorie is referring to was associated with the early beta version of the 1088XEL where there were problems with some standalone PSUs, but that got remedied by improving the DC filtering on board, so most any 2 Amp or greater supply with a center positive and the correct size plug should work fine now.

 

Thanks I have identified a local power adapter https://www.jaycar.co.nz/27w-3-12vdc-switchmode-plugpack-with-usb-outlet/p/MP3316

Edited March 26, 2018 by Lavalamp

[AtariGeezer]

Okay, I have a perplexing problem with the sound output:

 

I have key click sounds coming out on both channels, so the buffer amps are working.

I don't have the sound from Pokey appearing on the same outputs.

I do have sound from Pokey on each pin #1 of RN3 and RN4.

All 3 resistors in RN3 and RN4 read 100k...

 

Any thoughts?

[+DrVenkman]

Okay, I have a perplexing problem with the sound output:

 

I have key click sounds coming out on both channels, so the buffer amps are working.

I don't have the sound from Pokey appearing on the same outputs.

I do have sound from Pokey on each pin #1 of RN3 and RN4.

All 3 resistors in RN3 and RN4 read 100k...

 

Any thoughts?

 

Something to do with the Stereo settings in the BIOS?

[AtariGeezer]

I have Stereo Pokey Disabled and Pokey-2 IRQ Disabled so that only Sound from the Left Pokeyis used.

[+mytek]

Okay, I have a perplexing problem with the sound output:

 

I have key click sounds coming out on both channels, so the buffer amps are working.

I don't have the sound from Pokey appearing on the same outputs.

I do have sound from Pokey on each pin #1 of RN3 and RN4.

All 3 resistors in RN3 and RN4 read 100k...

 

Any thoughts?

 

So with key clicks being heard, as you said that confirms that the buffer amps are indeed working. And if you have Pokey sound on pin #1 of the resistor networks, but nothing coming out of the buffer amps, then it's beginning to sound like you have the wrong type of networks (bussed instead of isolated). Not much else could be wrong unless a pin or two of the resistor networks isn't soldered, or bridged to ground.

 

Bottom line is that we know the design as is works, and has been proven so by many people now. So it's got to be either wrong part or a soldering issue.

 

Just out of curiosity, if you put this into stereo mode and play a stereo Pokey tune, do you hear anything? If not then it's really leaning towards the wrong type of resistor networks being used.

 

1088XEL Schematic (look at page 4)

[AtariGeezer]

Both RN3 and RN4 have the ( 3 ) 100k resistors as shown on the schematic and have been ohmed out to verify.

Also checked for shorts.

[+mytek]

Both RN3 and RN4 have the ( 3 ) 100k resistors as shown on the schematic and have been ohmed out to verify.

Also checked for shorts.

 

Hmm... well that certainly makes for a mystery. Not much else springs to mind, but obviously something isn't correct in your build that is at the root of the problem. I just don't know what that would be at this point. I wish I could be of more help, but remote troubleshooting is difficult at best.

[AtariGeezer]

Yep, it's perplexing

Could you tell me what voltages you have on Pins 1, 2, 3 and 6 on either RN3 or RN4 ?

[+mytek]

Yep, it's perplexing

Could you tell me what voltages you have on Pins 1, 2, 3 and 6 on either RN3 or RN4 ?

 

I dob't have access to a 1088XEL at the moment, but I'll check that tomorrow and post the information (assuming no one else beats me to it).

[flashjazzcat]

Yep, it's perplexing

Could you tell me what voltages you have on Pins 1, 2, 3 and 6 on either RN3 or RN4 ?

 

c. 0.67V on pins 1, 2, and 3, and 3.3V on pin 6 (both networks).

[AtariGeezer]

 

c. 0.67V on pins 1, 2, and 3, and 3.3V on pin 6 (both networks).

Thanks Jon

[AtariGeezer]

Made some progress with my sound problem, First I had a bad Right Pokey and the Second problem appears that Q4 has a bad B-E junction where 0.6 volts is always seen on Q4's Base and Pin #2 on U9 (Pulled U9 to verify ).

 

So in Mono Mode, that 0.6 volts passes through to Pin #15, thus disabling Q3 and no Sound from the Right channel.

 

Tomorrow I swap out Q4 and with a bit-o-luck, it will work as it should

[Lavalamp]

It turned out my DIGIKEY 5v/2amp was working fine, but I get no 5v LED, what would I check next?

[+mytek]

It turned out my DIGIKEY 5v/2amp was working fine, but I get no 5v LED, what would I check next?

 

The LED might be backwards. If you check the power bus with a volt meter do you see 5 VDC when you press the power switch? This can be checked on one of the 14 pin HCT series chips (pin 7 = GND, pin 14 = 5 VDC). You also need to have the 555 timer installed to be able to switch on the power.

 

Also check out this link: http://atariage.com/forums/topic/272817-1088xel-atari-itx-motherboard-diy-builders-thread/page-11?do=findComment&comment=3938060

[Lavalamp]

 

The LED might be backwards. If you check the power bus with a volt meter do you see 5 VDC when you press the power switch? This can be checked on one of the 14 pin HCT series chips (pin 7 = GND, pin 14 = 5 VDC). You also need to have the 555 timer installed to be able to switch on the power.

 

Also check out this link: http://atariage.com/forums/topic/272817-1088xel-atari-itx-motherboard-diy-builders-thread/page-11?do=findComment&comment=3938060

 

Hang on, so the square pads for LEDs are negative,but elsewhere on the board its positive?

[flashjazzcat]

Square pads often signify pin 1. This does not necessarily imply polarity.

[+mytek]

 

Hang on, so the square pads for LEDs are negative,but elsewhere on the board its positive?

 

It is unfortunate that the square pad which is being used to represent positive for the electrolytic capacitors , turns out to be the negative lead instead for the LEDs. But the square pad usage is correct, since it denotes the cathode connection of the LED, and is also the same usage for the 1N914 diodes on the board as well. However most people would usually not know the difference and instead follow the board's silk screen which does correctly and quite clearly show the proper orientation of the LED. Always best to go by the silkscreen representation when assembling PCBs.

 

 

So if you look around the net, you'll see that square pad usage is most often used for the cathode on diodes and LEDs, + on a capacitor, and to designate pin one on a connector, header, or a SIP resistor network. I have followed this convention. Sorry if that caused any confusion.

 

Reference

 

Edit: BTW any place else that an LED connection is depicted to a header, the pin 1 marking of the header takes precedence, and in no way confers polarity.

[Lavalamp]

 

It is unfortunate that the square pad which is being used to represent positive for the electrolytic capacitors , turns out to be the negative lead instead for the LEDs. But the square pad usage is correct, since it denotes the cathode connection of the LED, and is also the same usage for the 1N914 diodes on the board as well. However most people would usually not know the difference and instead follow the board's silk screen which does correctly and quite clearly show the proper orientation of the LED. Always best to go by the silkscreen representation when assembling PCBs.

 

 

So if you look around the net, you'll see that square pad usage is always for the cathode on diodes and LEDs, + on a capacitor, and to designate pin one on a connector, header, or a SIP resistor network. I have followed this convention. Sorry if that caused any confusion.

 

Reference

 

Edit: BTW any place else that an LED connection is depicted to a header, the pin 1 marking of the header takes precedence, and in no way confers polarity.

 

 

Thanks for that! Every day is a school day!

[+mytek]

Thanks for that! Every day is a school day!

 

I made a small correction in my last post from 'always' to "...most often used for...", since I'm sure there will be some people doing it differently.

[+DrVenkman]

Not to berate Lavalamp, but as a note/warning/reminder to folks who later begin a build, it’s probably worth telling everyone who starts to at least scan through the (many!) pages of the entire thread - at this point, 4+ months since people began building, there’s a good shot someone has already had the same assembly issue or made a mistake they might avoid.

 

E.g., I installed my power LED’s backwards waaaaay back in January (and many pages earlier!) and all this was covered there. I hate for Michael to feel like he has to repeat these lessons every time one of us has made a mistake.