AY-3-8912 for the Coleco ADAM..?

[CharlesMouse]

Hmm, I seem to be posting a lot for a confirmed lurker... I promise I'll stop soon.

 

I mentioned on the other thread I started that I was looking in to doing an AY sound chip upgrade for the ADAM.

 

Why?

Well, there's some marvellous SGM games to be played but I don't have a SGM. Also, as I understand it, the ADAM will run a good deal of the SGM catalogue... quietly! (I added an extra 64k to mine a while ago)

 

As my main interest in old computers is tinkering with them I thought I'd take a crack at a SGM-compatible sound board to stick in my ADAM. I guess it would work in a Colecovision too, but without the extra RAM I don't know how useful it would be...

 

The plan:

-Come up with an AY-based design that won't be too hard to make

-Do it on the cheap, so try to stay away from expensive or hard to find components

-I really don't like having bare PCBs dangling out of my machines

 

With these thoughts in mind I decided to leave the expansion port alone and see if I could make a board that would fit in place of the Z80 as (nearly) all the required lines should be there and DIL-40 sockets aren't exactly rare.

The only required line that I'm aware is missing at the Z80 is the Audio-in to be found on Pin 31 of the expansion connector, so that will have to be a flying lead - either to be soldered somewhere suitable or as a separate line-out.

(As an aside when I did a Mockingboard clone for my Apple IIs I made sure to keep the dual AYs outputs separate for stereo but as the ADAM has only one audio-in that I know of this early prototype is mono)

 

I've attached screen-shots of my first attempt at a schematic and PCB layout. I should point out I'm aware space around the Z80 is a bit tight and so far I've only eye-balled it for space...

...um, I'm also very new to the ADAM so the schematic may have some serious errors. I'd welcome advice and suggestions if anyone has them to share.

[chart45]

it will be a painfull job to install this board since you have to unweld the z80 to install a socket... if its a personal project good

[Geoff Oltmans]

If you wanted to do this internally, depending on what expansion cards you have you may be able to do it through one of the internal slots.

[CharlesMouse]

Thanks for the feedback. :-)

 

Yep, using an expansion slot would be an easier upgrade and if there's a general wish among others for me to go that route I certainly can... I do this stuff largely for my own amusement but if my 'designs' prove useful to others I'm always pleased and so am happy to take suggestions.

 

FWIW: My current reasoning runs as follows

-Fun hardware project, so it doesn't bother me if I have to desolder and socket the Z80

-I like to at least try to keep things neat and relatively stock-looking, hence using the Z80's lines

-I try to stick with cheap and easy to source parts, mostly because I am cheap and lazy

-With the plans I currently have I'm going to need all the available expansion ports

 

-Oh, Having actually measured I'll likely need to re-do the above layout as it will interfere with a bunch of passives SW of the Z80. Either that or it's board re-work time as well as socketing the CPU. Not a biggie, but the above layout came together so well it's a shame to abandon it.

 

Um, while we're on the subject of proper expansion slots does anyone have the pin-outs for J5 and J6..? As far as I can tell the TRM lists the signals but not the pins and I'm not sure I wholly trust/understand the schematic I have.

 

 

PS

I guess I'll never get my hands on an F18a so:

a) Does anyone have access to the schematics / gerbers / system files required to DIY one?

failing that

b) I know d*mn-all about the Ti9918 and as I'm asking questions, and lazy, does anyone know how 'compatible' the later (Yamaha) versions are?

-Software and pin-compatible - awesome

-Software compatible - ok, that's an adaptor board and maybe some wiring

​-Neither - give up, I'm a rotten coder

 

Thanks again.

Edited March 19, 2019 by CharlesMouse

[Tursi]

b) I know d*mn-all about the Ti9918 and as I'm asking questions, and lazy, does anyone know how 'compatible' the later (Yamaha) versions are?

-Software and pin-compatible - awesome

-Software compatible - ok, that's an adaptor board and maybe some wiring

​-Neither - give up, I'm a rotten coder

 

Thanks again.

 

They are "reasonably" compatible from a software interface only... pinouts are different and normally they host more than 16k of RAM (but it looks like 16k is legal). Software that uses undefined register bits tends to have problems (and in the TI world, we found there was more than we expected). Most stuff will likely work out of the box.

[NIAD]

Aside from the fact that you would prefer an internal option for the AY-3-8912 sound chip, have you seen the extrernal version that chart45 has already designed that is detailed in this thread:

 

http://atariage.com/forums/topic/285129-missing-sound-chip-for-adam-computer/?hl=%2Badam+%2Bsound+%2Bchip&do=findComment&comment=4159023

 

Not all ADAMs are created equal and can play SGM games sans AY sound output without the Opcode SGM connected. I have one that will and one that won't.

[mr_me]

...

 

PS

I guess I'll never get my hands on an F18a so:

a) Does anyone have access to the schematics / gerbers / system files required to DIY one?

failing that

b) I know d*mn-all about the Ti9918 and as I'm asking questions, and lazy, does anyone know how 'compatible' the later (Yamaha) versions are?

-Software and pin-compatible - awesome

-Software compatible - ok, that's an adaptor board and maybe some wiring

-Neither - give up, I'm a rotten coder

 

...

I thought an f18a mk2 update is planned. Did you ask? http://atariage.com/forums/topic/280138-f18a-mk2/

 

You're probably busy, not lazy.

Edited March 20, 2019 by mr_me

[Geoff Oltmans]

A while back I was starting to do schematic capture for a Yamaha 9938/9958 upgrade board. I'd like to do one using SRAM instead of DRAM (using a CPLD to demux the DRAM addressing) to reduce part count and use more modern RAMs.

 

I used to have a TIM board for my ADAM that I scavenged from a TI 99/4A, it worked, mostly. The first hurdle is that you must program the palette registers used by the older video modes as by default all the colors are set to black, so nothing would display. There were some other gotchas, but I like the idea of using a 9938 or 9958 on the ADAM, and I think a DIY project could be pretty inexpensive.

[CharlesMouse]

 

They are "reasonably" compatible from a software interface only... pinouts are different and normally they host more than 16k of RAM (but it looks like 16k is legal). Software that uses undefined register bits tends to have problems (and in the TI world, we found there was more than we expected). Most stuff will likely work out of the box.

 

Thanks for the reply, and info. :-)

I guess that's at least hopeful, I shall have to pull my finger out and take a proper look myself & see if I can do it.

 

Of course I'd much prefer an F18a at some point. I got the impression they were pretty-much permanently out of production, but I'd be very happy indeed to be proven wrong. More Googleing required...

 

Back on topic:

After further measurement my initial take on a Z80-socket AY board won't fit the Delta board of the ADAM without messing about with some caps. I've yet to check clearances in the Colecovision itself as I've just remembered the Expansion Module 3. So I've done an update for that, that will fit and happily the West pin of C88 looks to be a good spot to hook-up the AY's output.

Oh, and I quite understand that if there is anyone interested in following along they may not be that charmed about desoldering the Z80 from their precious, and likely delicate, ADAM so I've come up with two further options:

1) I've done a spin on the board that should work in the side-expansion socket

2) It would be easier (but permanent) to first solder my Z80 board's pin-headers to the shoulders of the Z80 and then solder the otherwise completed board to them. I really, really wouldn't do that until I've at least proven this design actually works!!!

 

Please find attached piccies of my schematics and boards. I'll zip-up the Eagle files and post Gerbers if anyone's interested. I don't know when I'll get round to having the Z80 board made, but will at the least let everyone know how it goes...

 

PS

Yes, the boards have good VCC and GND fills (for two layer boards) but not shown in the images as as not to obscure the traces.

Edited March 23, 2019 by CharlesMouse

[Tursi]

Of course I'd much prefer an F18a at some point. I got the impression they were pretty-much permanently out of production, but I'd be very happy indeed to be proven wrong. More Googleing required...

 

Don't buy into the rumor mill. I work with the guy who makes them and we talk almost daily about it. V2 is coming. Hobby projects are just subject to real life interference.

[CharlesMouse]

@Tursi:

Thank you very much for the most welcome information. If it's not too cheeky for me to ask would you mind letting the chap who makes these I'd really like one, along with an ADAM adaptor board if the new version requires that, when v2 is out?

 

Many thanks and do please pass on my sincere thanks for his efforts on this excellent project.

 

News:

I'm about to send off the Gerbers to Seeed Studio (my favourite DIY PCB fab house) to do a board or two based on my attempt. I'm having the Z80 socket version made as that's the one I'm interested in but I've also produced the necessary files for any who want to make their own but would rather go the side-expansion route...

...please be advised that if anyone is interested in making their own I would wait until I've reported back to (hopefully) say the design actually works. (Seed Studio usually turns jobs around in about 2 weeks) Also while the side-expansion version is all-but identical to the Z80 socket board I've no intention of making one of those myself so any who do go with that one will be using an untested design!

 

Gerbers for both are attached.

Coleco_AY_Z80_v2.zip

Coleco_AY_SidePort_v1.zip

[Tursi]

@Tursi:

Thank you very much for the most welcome information. If it's not too cheeky for me to ask would you mind letting the chap who makes these I'd really like one, along with an ADAM adaptor board if the new version requires that, when v2 is out?

No worries, but he uses his waiting list for that, so just make sure you're signed up at his page

[CharlesMouse]

No worries, but he uses his waiting list for that, so just make sure you're signed up at his page

Thank you again - I have now left a message.

[soviet]

Cool i could love to see this working

[CharlesMouse]

Update time:

 

I've constructed the board and attached it to my ADAM, see piccies.

 

Given my track record you may be wondering what I messed up this time?

 

As it happens so far nothing directly to do with the board, but here's a good one:

A while back I made a clone of the Mockingboard sound card for the Apple II - a very rare, very sort-after, and so very expensive device. It uses two AY chips for 6 channels of stereo sound.

I think I've still got about four of them left that I never got round to selling...

I designed the ADAM's AY board with the AY-3-8912 in mind because it's smaller than the ...8910 and while I intended it to go in my ADAM I wanted to see if I could get it to fit in a Colecovision too. I thought I had a bunch of ...8912's kicking about but when it came to fit one to my board what I actually have are ...8913's. Still fully compatible, but a smaller package than the ...8912 that I used.

 

-insert rude words here-

 

I briefly considered attacking the board with Kynar to make the ...8913 fit but as it's for my ADAM and will be a proper pain to replace once the machine is buttoned up that left me with two options:

1) Redesign the board - No. I'm tired of doing that now, and I'd have to wait on the new boards.

2) Go on to fleaBay and buy an overpriced ...8912 from a UK seller so I didn't have to wait too long.

 

What did I do? I went for option 3) of course.

I found a ...8912 in Bulgaria for a sensible price, but that would be a while coming so I de-soldered my Amstrad CPC612's ...8912 and put a socket in it's place. It's chip can go in the ADAM so I can play now and the 6128 can have the IC from Bulgaria when it arrives.

 

 

So does it work..?

I don't know. After pulling the IC from one computer, soldering in a socket, soldering a socket to the shoulders of the ADAM's Z80, checking I hadn't killed it, fitting the board over the Z80 and connecting up the audio line, then checking the RF shield still fits, I lost the will to live. I also added a switch for the 64k piggy-back mod in my ADAM so if for any reason I'm stuck without a RAM card I can just push a button and hey-presto!

I don't like doing this stuff when it's late and I'm in a bad mood, I'm making enough mistakes as it is. Testing tomorrow - wish me good fortune.

 

PS

For any that are interested there are a few ways to attach this board to the Z80 socket. The 'proper' way would be to replace the Z80 with a socket, solder some turn-pin headers to the sound board, pop the Z80 in to said board, and plug the lot in to the new Z80 socket.

Needless to say I didn't do that. Partly because life's too short, partly because I don't want to mess with an elderly CPU soldered to an equally elderly motherboard, partly because there's an easier method, and mostly because male turn-pin headers are for some reason stupidly expensive unless you wait on a shipment from China - yes, I'd run out of those too.

 

The plan:

-Spread some quality flux over the shoulders of the Z80's legs - important, it's an old IC and getting solder to stick might be an issue.

-Take a 40 pin socket, preferably of the turn-pin variety, and solder directly to the shoulders of the Z80's pins - actually not hard, just go easy and try not to apply too much heat to that old chip

-Fit another socket in the usual way to the sound board - a wire-wrap socket with longer legs would be lovely but they go for crewel prices too!

-Take third socket (most important that it's the turned-pin variety) and carefully sand down the plastic sides until the shoulders of the pins are exposed.

-Apply more flux to the wells of those pins and also to the previously soldered pins of the socket you fitted to the sound board

-Offer one up to the other and solder the two together trying hard not to melt the plastic too much - solder doesn't like it.

-Make sure the test for continuity and bridges on all pins

 

The board will now plug quite securely in to the Z80 without resorting to major PCB surgery or wasting money on carpet-bagging b_ggers on eBay.

 

For info my retro computing background is the BBC Micro and it's descendants. Possibly the best series of 8bit machines ever made, but I'll not argue about it. If they have a down side it's that internal upgrades need to be plugged in to sockets. After 40 years the chances are any old upgrades you find will have had some connection pins snapped off, so you learn how to repair them.

Edited May 9, 2019 by CharlesMouse