Poorly Atari 1040STE

[rubber_jonnie]

Well all checked for shorts and none found. Which is good I guess. I have checked with my 'cheapy scope' and can see the signal on the /OE pin is going high from switch on. The /CE line isn't moving. When I check the /CE line with a multimeter the reading is 0v. When I check the /OE pin with a multimeter I get a reading of 5.17v. the /OE pin on the ROM is supposed to be active low but it's showing a voltage and when scoped I can see the pin is always HIGH.

I have checked the RESET pin on the MC68000 too and found that this pin is running high too from switch on, the XHALT pin as well is running high too.

So what else would I need to check from here.

Regards,

Brett

I think the cheapy scope is going to hinder you TBH, you really need to see what's actually happening on /CE and /OE. Did you check /CE and /OE at the PLCC socket?

I'd have to check my own machine to see what's going on, but I won't be able to until later in the week I'm afraid and you aren't going to really get a picture with a multimeter. It might register 5v, but it doesn't have the ability to tell you if it's going low as well

If /HALT is high on the CPU that's fine, it is active low. /RESET can easily be tested by pressing and holding reset and using the multimeter to probe it. It should drop to 0v with reset held and jump to 5v on releasing reset.

I still think something is broken tracewise somewhere, you just need to find what.

[BrettRogersUK]

I think the cheapy scope is going to hinder you TBH, you really need to see what's actually happening on /CE and /OE. Did you check /CE and /OE at the PLCC socket?

I'd have to check my own machine to see what's going on, but I won't be able to until later in the week I'm afraid and you aren't going to really get a picture with a multimeter. It might register 5v, but it doesn't have the ability to tell you if it's going low as well

If /HALT is high on the CPU that's fine, it is active low. /RESET can easily be tested by pressing and holding reset and using the multimeter to probe it. It should drop to 0v with reset held and jump to 5v on releasing reset.

I still think something is broken tracewise somewhere, you just need to find what.

Yeah I did check them at the PLCC. Without knowing where the /OE gets its signal from on the ROM Switcher board I don't have anywhere to try and find continuity to.

I can't see anything happening on /CE on the scope. I have checked with the scope and there's no movement at all on the /CE pin, I check it with a meter and check the voltage and I'm seeing 0v on the /CE pin (pin 3). The /OE pin is showing 5v when probed with a meter and I can see the signal going high when on the scope. Some reference images would be nice so I can check against what I'm seeing on the cheapy scope.

When checking the Reset pin on the 68000 chip can I see on the scope that when I press the reset button I can see it going low and then it rises again after I've released the switch so it would seem that all is ok there. I think the main problem is somewhere around the TOS switcher board but I can't find anywhere else to check. I've done all the checks suggested and they've all come back OK.

Can anyone clarify for me if the output pins on the PLCC chip on the switcher board all correspond to the data pin/lines that go to the Atari? A0-A17 address lines and O0-O15 Data lines? If they do then I can check continuity from the PLCC to the HI / LO pins themselves.

If there isn't continuity between any of the pins on the PLCC to the HI / LO rom pins that go to the motherboard then what should I do?

Thanks,

Brett

[rubber_jonnie]

Yeah I did check them at the PLCC. Without knowing where the /OE gets its signal from on the ROM Switcher board I don't have anywhere to try and find continuity to.

I can't see anything happening on /CE on the scope. I have checked with the scope and there's no movement at all on the /CE pin, I check it with a meter and check the voltage and I'm seeing 0v on the /CE pin (pin 3). The /OE pin is showing 5v when probed with a meter and I can see the signal going high when on the scope. Some reference images would be nice so I can check against what I'm seeing on the cheapy scope.

When checking the Reset pin on the 68000 chip can I see on the scope that when I press the reset button I can see it going low and then it rises again after I've released the switch so it would seem that all is ok there. I think the main problem is somewhere around the TOS switcher board but I can't find anywhere else to check. I've done all the checks suggested and they've all come back OK.

Can anyone clarify for me if the output pins on the PLCC chip on the switcher board all correspond to the data pin/lines that go to the Atari? A0-A17 address lines and O0-O15 Data lines? If they do then I can check continuity from the PLCC to the HI / LO pins themselves.

If there isn't continuity between any of the pins on the PLCC to the HI / LO rom pins that go to the motherboard then what should I do?

Thanks,

Brett

/OE is at pin 24 on the headers into the mainboard.

I'm not 100% sure the pin layout at the PLCC socket, I'd need to look at a schematic for it, which I don't have.

You're starting to get into remove it all territory now, because you could spend literally weeks troubleshooting this and finding nothing, especially without a proper scope. At least if you remove it and fit sockets, you will have a better view of the damaged part of the mainboard before fitting the sockets.

This will need to be executed very carefully to prevent further trace and via damage, but it is likely your only option other than send it to somebody to fix.

Unfortunately I can advise you of things I'd look at, but I can't impart my troubleshooting experience, and doing this sort of thing without having a machine in front of you is really pretty difficult.

All I can really say at this point is, the symptoms shout ROM, you installed a ROM switcher and it broke. It's pretty unlikely to be anything other than that upgrade.

You don't know if the switcher worked in the first place, you can only surmise it should.

You do know the old ROMs worked, so you need to head back to the last working state if you can without damaging the machine further, and repairing the known damage along the way, and fitting sockets.

If you can restore it to working with the original ROMs in sockets, then you can remove the ROMs and plug in the switcher to the sockets. It should work like that, and if it doesn't then it's possible the switcher or ROM has a problem.

[exxos]

Have you looked at the STE schematic ? You can easily see where everything goes then .

CE on the TOS board is driven from the large SMT chip on the motherboard. Just use continuity test on your meter and hold one end on the TOS board and gently wipe the other end around the SMT chip. You don't even need to trace anything , if you get a beep, its probably fine. You can do the same with address and data bus to the CPU.

Check in CE on power up needs a good scope and can be hard to capture. You need to use reset as the trigger for you scope and CE on the other probe. Keep pressing reset so you see it trigger, you will see a couple of CE pulses low regardless of the ROM board. If you don't, your scope isn't good enough or the CPU isn't running , in which case, aside from a bad CPU, you might have simply killed your board.

[BrettRogersUK]

Ok,

I've had one more look at this. It seems I'm just going round in circles at the moment. Until I can get some sockets fitted and try and revert it back to original spec I won't be doing anymore with it now.

/OE on the PLCC seems to be connected to the CE pin of the headers (the one marked CE). /CE on the PLCC appears to be connected to GND. I've metered it and beeped it out through continuity.

Pin 3 of the PLCC is the /CE pin and Pin 22 of the PLCC is the /OE. All the data and address lines are beeping out using continuity from the headers to the PLCC chip.

I've also checked continuity from the CE header pin and PLCC to pin 9 of the SMT chip. I think it's U400. And that checks out as a continuity check.

As I have, by all accounts, a crap scope it's all I can really do at this point. Until my sockets arrive there's not a lot more I can do to be honest. I have done all I can up to this point. All address and data lines all check out where they go and all Voltages seem to be correct across the board too.

There's obviously a reason why it's only booting to a white screen and going no further but unfortunately it's not making itself obvious!

Thanks,

Brett

[rubber_jonnie]

Ok,

I've had one more look at this. It seems I'm just going round in circles at the moment. Until I can get some sockets fitted and try and revert it back to original spec I won't be doing anymore qith it now.

/OE on the PLCC seems to be connected to the CE pin of the headers (the one marked CE). /CE on the PLCC appears to be connected to GND. I've metered it and beeped it out through continuity.

Pin 3 of the PLCC is the /CE pin and Pin 22 of the PLCC is the /OE. All the data and address lines are beeping out using continuity from the headers to the PLCC chip.

I've also checked continuity from the CE header pin and PLCC to pin 9 of the SMT chip. I think it's U400. And that checks out as a continuity check.

As I have, by all accounts, a crap scope it's all I can really do at this point. Until my sockets arrive there's not a lot more I can do to be honest. I have done all I can up to this point. All address and data lines all check out where they go and all Voltages seem to be correct across the board too.

There's obviously a reason why it's only booting to a white screen and going no further but unfortunately it's not making itself obvious!

Thanks,

Brett

As I said, all it took with mine was a single broken pin. The problem is in there somewhere, but stepping back is always a sensible option. You'll probably slap yourself when you find it, just be careful with desoldering the switcher.

[BrettRogersUK]

As I said, all it took with mine was a single broken pin. The problem is in there somewhere, but stepping back is always a sensible option. You'll probably slap yourself when you find it, just be careful with desoldering the switcher.

Thanks for your help and suggestion pal. Much Appreciated as always.

I will be very careful when removing the switcher. I've got some good quality solder wick on the way too to help me sucking remnants of solder away before I even think of lifting the board out. I'm gonna take plenty of photos as well of the back of the board so I know where all my 'bodge wires' go so I can put them back once the sockets are back in.

When you get chance would you be able to get me some readings from your STE. Voltages on /CE and /OE on the PLCC mainly and see what happens with yours. Just so I have something to compare to.

No rush now. Only when you get chance.

Regards

Brett

[rubber_jonnie]

As I said, all it took with mine was a single broken pin. The problem is in there somewhere, but stepping back is always a sensible option. You'll probably slap yourself when you find it, just be careful with desoldering the switcher.

Thanks for your help and suggestion pal. Much Appreciated as always.

I will be very careful when removing the switcher. I've got some good quality solder wick on the way too to help me sucking remnants of solder away before I even think of lifting the board out. I'm gonna take plenty of photos as well of the back of the board so I know where all my 'bodge wires' go so I can put them back once the sockets are back in.

When you get chance would you be able to get me some readings from your STE. Voltages on /CE and /OE on the PLCC mainly and see what happens with yours. Just so I have something to compare to.

No rush now. Only when you get chance.

Regards

Brett

No worries Brett, hope you can get there :)

[BrettRogersUK]

Well......... as expected, when removing the switcher using my new desoldering gun, more tracks lifted (I don't know why, I was being very careful) when removing it. It was mainly the links between the address lines on the HI/LO rom sockets that lifted. So I traced these and put them right.

I have put these right with wire on the underneath connecting each one together as it would be originally but with wire on the underside of the board. I have put sockets in now where the roms should go and made all the connections good again. Checked for shorts and checked all connections to CPU, DMA, BLITTER just about every chip that as the address and data lines going to it has been checked. Every address and data line checked across the board and getting continuity all over. Getting 5.17v across the board.

And guess what........... still the white screen, no floppy drive activity (despite the gotek being plugged in and usb stick fitted), no 'pip' sound when pressing any keys on the keyboard, ABSOLUTELY NOTHING! I've even tried pressing the reset button but that doesn't make it spring into life.

I have no idea what to try now. The PSU has been replaced. I've even put the original TOS ROMS back in. I've put the original 1MB of ram in (4x256k). PSU is a brand new one from Exxos store.

I've got a diagnostic cartridge but with nothing showing on the screen except a load of whiteness I'm not sure it'll be much help.

I'm not sure where to go from here as by all accounts a white screen is good and shows that things are working (in a fashion) but doesn't give any indication at all where a fault may lie.

Thanks,

Brett

[derkom]

I've got a diagnostic cartridge but with nothing showing on the screen except a load of whiteness I'm not sure it'll be much help.

Have you got any diag cart output over serial?