Plus Cartridges and custom EPROMs

[arnoldemu]

Well, I programmed an EPROM (when I found one that was actually blank - damn Chinese eBay sellers!).

And guess what.  I doesn't work.

So I guess I'm going to have to check all the solder connections on my board?
Or have I fecked the ASIC like Bryce said I would?  I only used a 12w soldering iron as per the CPC Rulez.  But I didn't cut the legs of the original ROM (as they didn't either). 

I get nothing on Plus boot-up, just black screen of the pink with lines that you get when ASIC doesn't connect.

I think Bryce meant the eprom.
But I think you are worried about the ACID?

Well, difficult to know what's happened.

[Bryce]

Oh, that doesn't sound good. Are you sure that the image you burnt to the EPROM was a good one (with the header removed etc) and did you verify that it was properly burnt to the EPROM? These would also cause the CPC to react that way.

If all is OK with the EPROM, then you probably have fried the ACID chip, which would be rather annoying.

The 12W specification of the Iron isn't really the important factor, the temperature of the iron is very importantant and also, that you don't hold it on any pin for more than around 2-3 seconds. Too hot or too long will definitely destroy any IC.

Bryce.

Edit: @Arnoldemu, It was the ACID that I cautioned he might destroy, which is why I suggested cutting the EPROM off to reduce the time required for de-soldering.

[redbox]

Oh, that doesn't sound good. Are you sure that the image you burnt to the EPROM was a good one (with the header removed etc) and did you verify that it was properly burnt to the EPROM? These would also cause the CPC to react that way.

Yes, I tried the AMSDOS/ParaDOS image and the Switchblade one.  I converted both from CPR to BIN using CPR Tools.  I then programmed them and verified them using the programmer and all came up ok.

If all is OK with the EPROM, then you probably have fried the ACID chip, which would be rather annoying.

Sh*****************t!  I did try to have the iron on the pin for as little time as possible, but I did muck it up a couple of times, so maybe that's when it happened.  I will have to get another one.

It was the ACID that I cautioned he might destroy, which is why I suggested cutting the EPROM off to reduce the time required for de-soldering.

I'm not worried about destroying the ROM, just the ACID.  I thought you suggested cutting the ROM legs so that I didn't conduct heat through the circuit and up to the ASIC, or am I getting this wrong?  Is it just so I can get it out quicker?

[Bryce]

I assume you mean the ACID when you say ASIC (the ASIC is in the CPC so it shouldn't be effected). The reason for cutting the EPROM off is so that each pin can be removed very quickly and the heat doesn't spread over to the ACID through the PCB tracks. If you try to get the EPROM out in on go, then you have to put the iron on each pin several times, which will most likely destroy the ACID from the excessive heat. Which I think you've just found out

Bryce.

[redbox]

I assume you mean the ACID when you say ASIC (the ASIC is in the CPC so it shouldn't be effected). The reason for cutting the EPROM off is so that each pin can be removed very quickly and the heat doesn't spread over to the ACID through the PCB tracks. If you try to get the EPROM out in on go, then you have to put the iron on each pin several times, which will most likely destroy the ACID from the excessive heat. Which I think you've just found out

Thanks for the explanation Bryce and I know I should have listened to you in the first place!  I also watched some YouTube videos about doing similar things and they all cut the chip legs first like you suggested.

The reason I tried to get the ROM out whole is because I wanted to put it straight back into the socket to check it as I didn't have the programmer setup when I started (but I put paid to that myself by breaking a pin on it anyway) and also because I saw they'd done it on CPC Rulez - I expect that they did it a lot quicker and are much more experienced than me though.

Anyway, I'll get another cartridge and try again.  The Willem EPROM programmer is really good btw and I would love to make some stuff with it in the future - hardware is cool!

I had a thought about the custom EPROM cartridge: wouldn't it be good it there was a cartridge extension cable with an edge connector (to plug into the Plus) linked to a socket on the other end that you plugged the cartridge into.  This would mean that on the cartridge you could use a ZIF socket (which you can't on a normal plug straight in cartridge because of the height restriction) and rest it on top of the Plus.  I saw the same blue ZIF that's in my Willem on eBay for a couple of quid and if you combine this with one of the IC sockets I'm trying to solder in it gives you the clearance you need over the ACID to put it straight on top...  What do you think?  Or is it hard to get the edge connectors wired up etc?

[Bryce]

No, now that I have a plus too, I was thinking of doing something similar, but my plan was to make a card with 1 ACID but 4 normal Sockets and a Dip-switch to choose which ROM is activated. That way I can have my 4 favourite titles on hand without having to do much IC switching. The only slightly difficult bit is that it has to be a double-sided PCB.

Bryce.

[TFM]

Well, for one of the four sockets you should use a Textool-socket, since the "favorite" ROM can change after some time ;-)

[Bryce]

A Texttool / ZIF socket is a very expensive part (€11.70 for 1 = €46.80 for 4!!!) just to swap the EPROMs occassionally. On an EPROM burner they make sense, but not on a Multi-cartridge system.

Bryce.

[TFM]

A Texttool / ZIF socket is a very expensive part (€11.70 for 1 = €46.80 for 4!!!) just to swap the EPROMs occassionally. On an EPROM burner they make sense, but not on a Multi-cartridge system.

Bryce.

Fair enought. I was just thinking how it would be in my case. I would burn my four favorites, but after using them a while .... well, you long for something new then.

Right, thery are expensive. But one of them probably could make sense :-) Imagine you meet a friend of go to a CPC meeting and you intend to show somebody the 20 Plus games that you have on EPROM ;-)  I mean ... come on ... one textool equals three beers ;-)

[redbox]

A Texttool / ZIF socket is a very expensive part (€11.70 for 1 = €46.80 for 4!!!) just to swap the EPROMs occassionally. On an EPROM burner they make sense, but not on a Multi-cartridge system.

There are ZIF sockets on eBay for £3.50.  I hope to use one on my cartridge when I stop frying ACIDs     

Got my new cart today to try again.  So I am guessing I should cut the legs first (looks difficult as the ROM is low in the PCB with not much leg exposed - any ideas?) and then desolder/pump really quickly (under 2-3 seconds per pin), put IC socket in then re-solder really quickly... is this right?

[Bryce]

Cut the legs as close to the chips body as possible so that the remaining pins are as long as possible. When the chip has been completely cut free, mount the PCB in a vice or PCB holder. To remove the pins, grip them on the chip side with a small pliers, apply the soldering iron and pull the pin with the pliers at the same time. This way you should only need to apply the soldering iron for a second or less and nothing should get damaged.

If you want to be really really sure, you could add a binder clip (like this one:  http://www.istockphoto.com/file_thumbview_approve/420111/2/istockphoto_420111-binder-clip.jpg ) on top of the ACID pins to absorb any heat that does make it to the ACID.

Bryce.

[redbox]

Great tips Bryce, thank you, will be sure to do that this time.

When I remove the old solder left after removing the ROM, should I just be really quick again with the soldering iron and pump?

And when I solder the IC socket back onto the PCB, I'm assuming be really quick again?  And what size solder would you recommend...?

[Bryce]

Exactly, always make sure the heat is there for the minimum amount of time and pause between pins to give it time to cool back down. The exact solder size isn't all that important as long as it's not way too large. I normally use a 0.75mm solder - Leaded! Because this whole ROHS thing is a joke and CPCs weren't ROHS to start with anyway.

Bryce.

[redbox]

I have started with another cartridge and taken all the precautions this time...!

But I have come across another problem: on the pin holes where I have removed all the solder, when I try to resolder the IC socket pins, the solder won't stick.  It only sticks on the pin holes where some of the old solder remains for it to join to.

I bought a flux pen and tried applying that but the solder still won't stick.  Any ideas?

[Bryce]

Either it's not getting hot enough (ie: the iron is touching the pin but not the pad) or it's a problem due to trying to mix unleaded and leaded solder.

Bryce.

[redbox]

Ah I see, my solder is lead-free and I'm guessing the 1990s Amstrad solder is leaded...

Maplin didn't have any lead solder.  Probably some bullsh*t EU law about that!

Will get the iron hot and make sure I'm touching the base and report back.

[redbox]

It won't solder because the metal circle at the pinhole on the PCB I want to solder is missing.

I think it became removed when I unsoldered the pins.  So all that is left is the PCB board which the solder won't stick too.

[Bryce]

No, problem, depending which pin it is, you can either scratch the solder-mask off the track and solder a piece of wire to the pin and track to bridge the gap (if the track only goes to the edge connector) or if it's a pin that goes to a different component, then solder a wire bridge to the next solder point.

Bryce.

[redbox]

Looks a bit difficult (for a hardware n00b like me) as it's a double-sided PCB but will give it a try!

I think I might have pulled the metal circles at the pinholes (solder point?) off when removing the ROM legs that might not have been completely unsoldered, will have to be more careful (again).

[redbox]

I got another (!) cart, took all the precautions (including bulldog clip on the ACID) and... it seems to have worked.

Only slight snag is the only EPROM I have blown is a borked copy of the   normal Plus cartridge, but I think it was enough to prove the ACID is   working.

Thanks for all your help Bryce, really appreciated.  I will be back here when it breaks 

I now need my EPROM eraser to turn up so I can get some proper software on there!

[Bryce]

Congratulations. Pity you had to destroy some good ones to get there, but it's all experience gained and any future mods will be done with more confidence and hopefully success on the first attempt.

Bryce.

[arnoldemu]

Congratulations. Pity you had to destroy some good ones to get there, but it's all experience gained and any future mods will be done with more confidence and hopefully success on the first attempt.

Bryce.

talking about destroying cartridges.

I have two cartridges, both have EPROMs. Both didn't work to well so I stored them in a box along with other electronics (z80's, old 3" disc drive motors).
Have I damaged them by storing them with the motors? And have I damaged the other stuff in the box?

Anyway, I tried them out. One turns the screen black like it tries to execute something but the rom is blank, the other shows some corrupted lines and the usual pink/purple background, like it tried to initialise the crtc and failed.

So are they stuffed, or could they be reprogrammed to work?

(I wish I had an eprom eraser and programmer btw - perhaps it is time to invest in one)

Is there any way I could tell if the acid is responding by putting a basic multimeter on one or more pins or similar?

I would like to repair them if possible, or at least re-use them for a future project.

[TFM]

Well, you can replace the EPROM by a socket, then get a burned new EPROM and see it it works.

[Bryce]

Other than obvious physical damage, there are only two things that can damage the cartridge PCB:

1) Strong UV light (direct sunlight is enough) can and will delete or corrupt the program on the EPROM.

2) A static electrical dis-charge could damage either the EPROM or the ACID permanently.

Magnetism (from the motors magnets) has no effect on either of the ICs. There are other factors however, that could cause the cartridge to malfuntion. Oxidised contacts will cause crashes / non-starts and is very easy to solve, you just need to clean the edge connection. Slightly more difficult are dry joints. This is when a crack appears in the solder joint. Under a microscope they are obvious but not always visible with just the naked eye.

If you're not sure and afraid you'll only damage them worse, send me them and I can check them out.

Bryce.

[redbox]

Anyway, I tried them out. One turns the screen black like it tries to execute something but the rom is blank, the other shows some corrupted lines and the usual pink/purple background, like it tried to initialise the crtc and failed.

These are exactly the kind of things I was seeing with my attempts at customising the cartridges with EPROMs.

After speaking to Bryce, I'm hopeful that it's just oxidised contacts or dry joints (my dodgy soldering!) and that the ACID isn't fried.

I wish I had an eprom eraser and programmer btw - perhaps it is time to invest in one

If you want some EPROMs programmed to test your boards, PM me and I'll send you a couple.