Atari Schematics Lost?

[Dropcheck]

I agree that the 1450XL could stand improvements galore,  in most of the subsystems in fact.  It's a prototype for sure.  For instance there's no Chroma connection on the monitor output jack.  There's a ton of upgrades/fixes I'd like to do.  I've already got a list of those on my to do list.  😀 

 

But I think my biggest hurdle right now is getting a functioning board.  😔

 

The first time should expose most of the really stupid mistakes and physical fit issues.  The second time should allow a functioning board with a few non-fatal errors to correct.  The third time is the refinement and nitpicking board.  At least that's been my experience such as it is.  I hope there won't be a fourth.  A $150 board manufacturing cost each time is not sustainable beyond 3 or 4 tries.  🤕

 

This board is a big one, measures out about 351mmx242mm.  Is four layers and is all TH parts for right now.   But with the rapid EOL of a lot of TH parts, it's likely I'll have to redesign a partially SMT board pretty soon so that it has some kind of life span once I release the project to PD. 

 

uh oh.... Weather coming in.  I'll post again hopefully later this afternoon

 

 

[+mytek]

4 hours ago, Dropcheck said:

A $150 board manufacturing cost each time is not sustainable beyond 3 or 4 tries.  🤕

We've all waited this long to have a 1450XL(D), I'm sure a bit longer won't hurt anyone. So instead of another attempt at a stock motherboard, maybe it's better to take your time and integrate whatever changes you wish to do in the 2nd revision. That way you can perform a full test of everything. Most likely there would still be a need for one more revisions beyond that, but that would only be to fix minor issues, with that 3rd revision being golden.

 

Usually I can knock it out of the park by my 3rd revision. Only rarely does it go beyond that. Keep in mind that there are a lot of proven open source motherboard designs floating around out there. So borrow whatever circuits you want from those, knowing that it has been shown to work. I do this all the time myself.

[reifsnyderb]

For what it's worth, I am in favor of making an exact replica first.  After that works, upgrades can commence.

[Overange]

12 hours ago, mytek said:

 

 

And if you wish to stick mainly to THT devices, there is a THT equivalent for all except the FMS6400 Video Buffer/Combiner. That chip gives very fine quality composite video output as well as separate Luma and Chroma for S-Video, without creating any bleed issues between the signals. However it's obsolete, but not a problem to purchase as NOS from eBay or AliExpress, and really not subject to being faked like some other popular chips.

 

 

Talking about the FMS6400 and it being obsolete / hard to find etc etc, I was looking at this project for the c64:-

 

https://www.pcbway.com/project/shareproject/Commodore_64_128_RF_Video_modulator_bypass_replacement_Jail_bars_removal_long_sh_6e44f5bb.html

 

 

The video amp is still available:-

 

https://www.mouser.co.uk/ProductDetail/Texas-Instruments/THS7316DR?qs=6RlL8P85hLFYQz9iBjivBA%3D%3D

 

Have you seen it before and do you think it could work with in the UGV?

 

 

[+mytek]

4 minutes ago, Overange said:

Have you seen it before and do you think it could work with in the UGV?

I've used its cousin the THS7314 in a different project. However it appears to have a fixed 6 db gain factor built-in, whereas the FMS6400 in the UGV has been set to 0 db gain. In the early development days I had tried the FMS6400 set to 6 db gain and found it introduced too much noise. Also although the package size is the same, the pin-outs are not. Bottom line is that it wouldn't be a drop-in replacement, and would require some R&D to ascertain if it was suitable. Oh and lastly it has no built-in summing aspects to be able to create the composite signal, so that would need to be done externally while having the possibility of introducing bleed into the S-Video aspect.

 

Good find though, and at an inexpensive price point.

[+kheller2]

17 hours ago, mytek said:

Well just my 2 cents - the Atari engineers didn't always know what they were doing, and as such made some design decisions that either made things worse or were totally unnecessary when moving from one model to the next.

 

If the 1450XL(D) board was a 4-layer type, then you are far better to dedicate one plane completely for the GND bus and another for the +5V. What does matter more than independent GND and +5V regions, is to simply isolate analog from digital circuits. So for instance if at all possible, all analog should be located grouped together and as far away from high-speed digital clocking circuits.

 

 

 

So something like this?

 

https://atarimuseum.ctrl-alt-rees.com/computers/8bits/1200xl/documents/better_1200_memo-10NOV82.pdf

 

[+mytek]

5 minutes ago, kheller2 said:

 

So something like this?

 

https://atarimuseum.ctrl-alt-rees.com/computers/8bits/1200xl/documents/better_1200_memo-10NOV82.pdf

 

That looks like a 2-layer board because of the old style gridded ground plane from back when PCB manufacture was a subtractive process, which saved etch-chant. But the separation of analog and digital is indeed what I was referring to.

 

EDIT: When using a solid inner ground plane on a 4-layer board, the resistance is nil across the plane, thus between any two points you will have a good ground path, and there is very little chance of creating a ground loop.

[Dropcheck]

Update:

 

Major Fail.  GND and +5V are tied together on the new boards.  Didn't discover it until I had most of the board populated with the sockets and passives.  Soldered in a couple of transistors wrong and after removal, went to ohm out the holes to make sure I hadn't boogered them and noticed that probing +5V and GND were giving me 0 ohms.  A dead short.  Tested a bare new board.  Same.  Worthless. 🥹

 

Trying to figure out if it was me or JLCPCB.   

[reifsnyderb]

1 hour ago, Dropcheck said:

Update:

 

Major Fail.  GND and +5V are tied together on the new boards.  Didn't discover it until I had most of the board populated with the sockets and passives.  Soldered in a couple of transistors wrong and after removal, went to ohm out the holes to make sure I hadn't boogered them and noticed that probing +5V and GND were giving me 0 ohms.  A dead short.  Tested a bare new board.  Same.  Worthless. 🥹

 

Trying to figure out if it was me or JLCPCB.   

Are they tied together at a single location (or two) that can be found and broken?

[+kheller2]

How would you find that!?!?

[Dropcheck]

1 hour ago, reifsnyderb said:

Are they tied together at a single location (or two) that can be found and broken?

In Diptrace, looking at both my schematic and board layout, I'm not seeing both signals lighting up when I click on one or the other.  So as far as the program is concerned, I have not tied them together.  The next step is checking the routed board layout. 

[reifsnyderb]

3 hours ago, Dropcheck said:

In Diptrace, looking at both my schematic and board layout, I'm not seeing both signals lighting up when I click on one or the other.  So as far as the program is concerned, I have not tied them together.  The next step is checking the routed board layout. 

I just happened to think about a problem I once had with JLCPCB.  On a 4 layer board, I had made, they once drilled through a power trace on the 3rd layer.  This resulted in a chip not having power.  My solution was to run a short bodge wire.  The next time I had that board made, I moved the power trace so they could drill the holes.

 

I remember some talk about the Tong board possibly being 4 layers.  Is this a 4 layer board?  If so, JLPCB drills some sort of alignment holes in at least 2 corners of a 4 layer board.  Hopefully this is something similar?  Hypothetically, if this is the issue, one of those holes could be shorting +5 and ground.

[+selgus]

10 hours ago, reifsnyderb said:

I just happened to think about a problem I once had with JLCPCB.  On a 4 layer board, I had made, they once drilled through a power trace on the 3rd layer.  This resulted in a chip not having power.  My solution was to run a short bodge wire.  The next time I had that board made, I moved the power trace so they could drill the holes.

 

I remember some talk about the Tong board possibly being 4 layers.  Is this a 4 layer board?  If so, JLPCB drills some sort of alignment holes in at least 2 corners of a 4 layer board.  Hopefully this is something similar?  Hypothetically, if this is the issue, one of those holes could be shorting +5 and ground.

Are you sure they drilled extra holes that weren't listed in your gerber files? I make 4-layer boards all the time with JLCPCB and never have they added extra holes I didn't specify. This could cause all sorts of problems with middle layers, etc.

 

I do have mounting holes in each of my designs, so maybe they just use those for whatever type of alignment you were referring to. Do you have non-plated holes in your boards for mounting?

 

One of the steps in the manufacture process at JLCPCB is to do a flying probe electrical test, which I assume would find errors with the manufacturing verses what the gerbers specify.

[Dropcheck]

Routed Board layout is clear.  So far does not appear to be something I did wrong.  Still checking, never say never. 

 

The bare prototype 1450 board I have on loan appears to be a four layer board.  My version is also four layer, with GND and +5V plane layers sandwiched between the top and bottom layers.  Could a knee-jerk ground copper pour I do on both the top and bottom layers have inadvertently tied the +5V and GND signals together when JCLPCB drilled holes?

[reifsnyderb]

36 minutes ago, selgus said:

Are you sure they drilled extra holes that weren't listed in your gerber files? I make 4-layer boards all the time with JLCPCB and never have they added extra holes I didn't specify. This could case all sorts of problems with middle layers, etc.

 

I do have mounting holes in each of my designs, so maybe they just use those for whatever type of alignment you were referring to. Do you have non-plated holes in your boards for mounting?

 

One of the steps in the manufacture process at JLCPCB is to do a flying probe electrical test, which I assume would find errors with the manufacturing verses what the gerbers specify.

I just checked a 4 layer board I had made recently and it didn't have the holes.  Maybe JLCPCB changed their procedure?  I know that older 4 layer boards had two extra holes drilled, one in each opposite corner, that I believe they used for aligning the boards.  I distinctly remember chasing a failure, for hours, only to find out one of these tiny holes were drilled through a trace then having to solder a small jumper in place to fix the problem.  Some of these boards are even out in the wild.  My latest boards don't have these holes.  I'd still check for the holes in the corners just to make sure.

[reifsnyderb]

40 minutes ago, Dropcheck said:

Routed Board layout is clear.  So far does not appear to be something I did wrong.  Still checking, never say never. 

 

The bare prototype 1450 board I have on loan appears to be a four layer board.  My version is also four layer, with GND and +5V plane layers sandwiched between the top and bottom layers.  Could a knee-jerk ground copper pour I do on both the top and bottom layers have inadvertently tied the +5V and GND signals together when JCLPCB drilled holes?

Normally, there are clearances between any vias and unconnected planes.  I don't know how Diptrace works, but KiCAD will find such a short.  I assume Diptrace would as well. 

[Dropcheck]

I believe I have a possible reason and it maybe a misunderstanding on my part how to do four layer boards in Diptrace.  I don't do that many and usually they are months and sometimes a year or two apart.  What i learned then I am forgetting now.  I can only keep so much in my head anymore and then it starts leaking out.  🙃

 

I'm going to do a test four layer board to verify my theory.   So until I get these boards back and test them out, this project is going on hold.  Hopefully no more than two weeks or so.

[+mytek]

On 6/5/2024 at 6:08 AM, selgus said:

Are you sure they drilled extra holes that weren't listed in your gerber files? I make 4-layer boards all the time with JLCPCB and never have they added extra holes I didn't specify. This could cause all sorts of problems with middle layers, etc.

Ditto. I've never had an extra hole that wasn't specified in the drill file that accompanies the gerbers when having JLC manufacture boards for me. And even though @reifsnyderb has made a lot of boards in the last couple of years, I'm sure I've got him beat for the time being

 

21 hours ago, Dropcheck said:

I'm going to do a test four layer board to verify my theory.   So until I get these boards back and test them out, this project is going on hold.  Hopefully no more than two weeks or so.

Or to save yourself some money, download and install gerbv to visually inspect each layer.

 

Here's an example using that program to analyze the 2 middle layers inside of one of my 4-layer boards.

 

Upper middle layer clearly showing the GND power plane connections

 

Lower middle layer clearly showing the +5V power plane connections

[Dropcheck]

19 hours ago, mytek said:

Ditto. I've never had an extra hole that wasn't specified in the drill file that accompanies the gerbers when having JLC manufacture boards for me. And even though @reifsnyderb has made a lot of boards in the last couple of years, I'm sure I've got him beat for the time being.

 

Or to save yourself some money, download and install gerbv to visually inspect each layer.

 

Here's an example using that program to analyze the 2 middle layers inside of one of my 4-layer boards.

 

Upper middle layer clearly showing the GND power plane connections

 

Lower middle layer clearly showing the +5V power plane connections

 

Unfortunately I've checked my gerbers  in both gerbv and Diptrace and GND and +5v pins seem to be indicated properly signal wise.  I'm beginning to think that Diptrace's "update all copper pours" was not used before I created the the gerbers and so any contamination of the various copper pours on the layers as it was routing was not cleaned up.  I'm still sending a test four layer board out to test that theory.  If only to more cheaply nail down the 1200 Style cartridge shroud and joystick holes.  They were still off in the last batch of boards.  

 

[Dropcheck]

Test boards came back and seem to confirm my suspicion.  Apparently I did not update the copper pours before I created the gerbers for the 2nd proto board.  I got into a hurry.  My cat's ears are still smoking.  😔

 

But I was able to more precisely nail down the cartridge shroud and joystick holes.  This time I'll go ahead and consolidate all the GNDs.   And then before I send the order out I'll check and then check and then check again.

 

Freaking impatience gets me every time. 

[Dropcheck]

First attempt at power on with a populated board, (well minus the modem jumper closed and the speech chip installed)

 

No display.  U16(CPU) and U17(Antic) are getting warm to nearly hot after a few minutes.   Most of the rest of the chips are cold.

 

I did do a cursory +5V chip power check with empty sockets.  But obviously something isn't right. 

 

I am unsure about the three PAL chips.  I was not able to program the PAL chips I had with the programmers I currently have.  Jurgen sent me PAL2GAL conversions to test.  So if someone actually has the ability to burn those PAL chips, I can send you some to burn for me.

 

 

 

In the meantime since more eyes the better I am posting my current schematic.  IT IS NOT FOR GENERAL RELEASE and LIKELY CONTAINS ERRORS!

1450XL_v1_3.pdf

[AtariGeezer]

@Dropcheck  Where did you get the pinout for the power supply??? Or did you change it on your build?

[Dropcheck]

3 hours ago, AtariGeezer said:

@Dropcheck  Where did you get the pinout for the power supply??? Or did you change it on your build?

 

I'll double check my schematic against the Atari made bare board traces and the connector and power plug/ps I'm using.  I may have mis-numbered the pins on my schematic for the power connector.

 

 

 

 

 

Edited September 5 by Dropcheck

[Dropcheck]

10 hours ago, AtariGeezer said:

@Dropcheck  Where did you get the pinout for the power supply??? Or did you change it on your build?

It appears that the power connector in my schematic is mis-numbered per this ps.  If I were using this power supply my board and chips would probably be toast. 

 

But this is not the ps I am using.  I am using a Mean Well RT-65A with a fully wired SDS-80J power plug that should be wired correctly for the connector.

 

 

 

I'll make the necessary changes to the schematic to reflect the 'correct' wiring of the power cable per the Atari PS.  It should be a simple re-connection at the MeanWell ps for the correct voltages per plug pin.  🙂

 

As I indicated the schematic released is not ready for production, only for testing at this stage.

[AtariGeezer]

2 hours ago, Dropcheck said:

It appears that the power connector in my schematic is mis-numbered per this ps.  If I were using this power supply my board and chips would probably be toast. 

 

But this is not the ps I am using.  I am using a Mean Well RT-65A with a fully wired SDS-80J power plug that should be wired correctly for the connector.

I'll make the necessary changes to the schematic to reflect the 'correct' wiring of the power cable per the Atari PS.  It should be a simple re-connection at the MeanWell ps for the correct voltages per plug pin.  🙂

 

As I indicated the schematic released is not ready for production, only for testing at this stage.

Cool, okay..  Just wanted to make sure you didn't accidentally get +5 and +12 backwards.  That would have been a real mess...

 

I looked at Brads site last night and don't see the PAL-A or PAL-B listed anymore.  I know I have 4 more PAL-C's (made by @bob1200xl 12 years ago), but will have to locate my 1450XL spare parts box in storage to see if I bought spares of the 2 other PAL Chips.  I usually try to buy at least two of most parts for the Atari builds.  I also have a spare speech chip in storage too that I was hoping to use in a 2nd build of the 1450xl if any more boards surfaced...