800XL Blue screen with a cursor.

[Beeblebrox]

Just now, psykix said:

BREAK didn't do anything. I tried blasting the Pokey with hot air but nada... Just waiting on replacement chip to arrive.

 

see my post directly above.  

[psykix]

Yeah, I replied as you did!

 

Don't think it's CTIA because I don't get any cassette loading sound. Plugging the 1050 in however.. that gives a whole load of Boot Error messages iirc.

 

Which chip is the PIA?

Edited April 29 by psykix

[Rybags]

The CPU is worth a look also.  If the IRQ pin isn't connected you can have trouble.

You could just check continuity between the CPU IRQ pin and Pokey and PIA.

PIA is a 6520, though could be labelled as 6820 - "Atari part # CO14795 or CO12298 - sometimes no Atari number, Hitachi HD68B21, GTEu G65SC21P" (from AtariMax Jindroush site mirror)

Edited April 29 by Rybags

[psykix]

I've socketed the PIA - no difference. I have continuity between CPU IRQ & Pokey & PIA.

 

I've checked power to the CPU, PIA & Pokey and have 5v.

 

I'll see what happens now when replacement Pokey turns up.

 

[Beeblebrox]

5 minutes ago, psykix said:

I've socketed the PIA - no difference. I have continuity between CPU IRQ & Pokey & PIA.

 

I've checked power to the CPU, PIA & Pokey and have 5v.

 

I'll see what happens now when replacement Pokey turns up.

 

if it turns out to be your Pokey chip that is bad - don't throw it away. It will likely work fine in a dual pokey chip stereo upgrade as the secondary pokey chip as the music function still works, it's the other fucntions that have just failed. Done that a few times now with such chips.  

[psykix]

Becoming a bit of a saga this.. Replaced Pokey and it is still the same...

 

I have no power LED now but I did previously.

 

The function keys are the only keys that work on the keyboard.

 

Still blue screen white cursor.

 

Also where Star Raiders would go to a black screen previously, now the computer just stays on blue screen white cursor. I do have power to the cartridge slot but not sure what to test beyond that.

 

Diagnostic cart works - audio test, RAM, ROM all pass. Keyboard test doesn't work apart from function keys, and although it recognises the OPT key, it says error.

Edited May 4 by psykix

[Beeblebrox]

41 minutes ago, psykix said:

Becoming a bit of a saga this.. Replaced Pokey and it is still the same...

 

I have no power LED now but I did previously.

 

The function keys are the only keys that work on the keyboard.

 

Still blue screen white cursor.

 

Also where Star Raiders would go to a black screen previously, now the computer just stays on blue screen white cursor. I do have power to the cartridge slot but not sure what to test beyond that.

 

Diagnostic cart works - audio test, RAM, ROM all pass. Keyboard test doesn't work apart from function keys, and although it recognises the OPT key, it says error.

Have you replaced the pia chip and or checked all inroads and out roads from pia, (traces, vias, sockets)? 

[psykix]

I haven't replaced the PIA but I did socket it. I'll take another look at it. I only have a multimeter so a little limited on the things I can check.

 

[Mq.]

I think you'd be better off giving this computer for repair to someone who has replacement chips and other motherboards for testing. Now, in my opinion, it is no longer possible to help over the internet. If you blindly replace all the integrated circuits one by one, you will spend a fortune. Maybe the problem is some cold solder, damaged track on the board, etc.

Edited May 4 by Mq.

[psykix]

I'm beginning to think that too!

[Beeblebrox]

14 minutes ago, psykix said:

I haven't replaced the PIA but I did socket it. I'll take another look at it. I only have a multimeter so a little limited on the things I can check.

 

No worries. It's just I fixed a 600xl with the same cursor issue last week and it was the pia and or it's socket that was to blame. Of course your machine could have multiple issues, (certainly with the issues with the power light), but worth making sure something you have socketed and the chip itself is OK. 

 

Could you post a hi res image of top and bottom of the board as it stands now? Also a hi res of the front and back of the pia socket, and solder work?

 

I am sure we can get to the bottom of it.

 

[psykix]

I've measured voltages on PIA and I've attached board photos.

 

Pin 1 -GND

Pins 2-10 - 5v

Pin 11 - NC

Pins 12-16 - 3.75V

Pins 17 & 18 - 5V

Pin 19 - NC

Pin 20 - 5V

Pin 21 - 4V

Pin 22 - 5V

Pin 23 - 4.65V

Pin 24 - 5V

Pin 25 - 1.97V

Pin 26 - 1.6V

Pin 27 - 1.4V

Pins 28-32 - 0.67V

Pin 33 - 0.6v

Pin 34 - 4.7v

Pin 35 - 3.4V

Pin 36 - 3.55V

Pins 37-40 - 5V

 

Some of those pins look a bit low going by the circuit diagram - I think 28-32 should be 1v?

 

[xrbrevin]

the PIA is an off-the-shelf part, not a custom chip so it is relatively inexpensive

further info here

[+kheller2]

Couple of thoughts….

keyboard not working: ribbon cable issues/ corrosion/ not seated right, goes through 4051s, then to pokey.  Silver keys go to other chips. You said you don’t have the power light coming on, check your ribbon and how it’s plugged in. 
 

how can you get boot error messages from the 1050 yet also a blue screen and stuck cursor?   Is the cursor only when not hooked to the 1050?  That sort of implies BASIC or MMU or PIA.   
 

however, can you boot with option down and run the self test…or is SALT the only thing working?
 

[TZJB]

2 hours ago, psykix said:

Becoming a bit of a saga this.. Replaced Pokey and it is still the same...

 

I have no power LED now but I did previously.

 

The function keys are the only keys that work on the keyboard.

 

Still blue screen white cursor.

 

Also where Star Raiders would go to a black screen previously, now the computer just stays on blue screen white cursor. I do have power to the cartridge slot but not sure what to test beyond that.

 

Diagnostic cart works - audio test, RAM, ROM all pass. Keyboard test doesn't work apart from function keys, and although it recognises the OPT key, it says error.

 

The power LED is fed from the keyboard connector pins 18 GND and 24 +5V via R95 220R

 

 

 

As the function keys are working via GTIA there must be a disconnect at R95 or J8 pin 24 as the power LED is unlikely to have blown (I say with confidence) 🙂.

 

The other keyboard keys are detected at POKEY through the 4051 multiplexers. As you have changed POKEY the J8 connector or the 4051 chips may be suspect.

 

 

 

Incidentally, I bought some Motorola 68B21P PIA chips a while ago and they work great. Make sure they have a B which indicates a 2MHz rating.

 

Plus, what @kheller2 said!

 

[psykix]

Thanks for the input. I should probably clarify the order of events, since I seem to have thrown some red herrings into the mix along the way. It's been a bit of a learning curve for me!

 

I got the Atari 800XL and 1050 out of the parents loft. Initially everything appeared to work fine, and I managed to load the first floppy disk that I tried. I went to load a 2nd disk and the 1050 appeared to have stopped working. I ended up replacing the 47uf caps in the 1050 and that appeared to come back to life. At least the drive motor was working again and the activity light was also behaving as it should.

 

I then went to try loading another disk and got a load of Boot Error messages scrolling down the screen. It was only later that I realised that I had the cable in the wrong port on the back of the 1050 which may have accounted for those errors.

 

I then tried a joystick and Star Raiders cartridge. The Atari booted to what I now know to be self diagnostics but I didn't realise at the time that the Star Raiders cartridge had self diagnostics on board.

 

I removed the cartridge and powered up the 800XL normally and this time it just went to blue screen and white cursor, and that's where I am at currently. Trying Star Raiders again, other than the first time just gave a black screen. Now however, it does nothing and the 800XL just stays on blue screen white cursor.

 

RE: the power LED.. this is a little embarrassing.. pin 24 on the ribbon cable had broken where it connects to the keyboard. I've repaired that with a little bit of kynar wire and have a working LED now.

 

Holding Option whilst booting does nothing. Holding Start whilst booting gives the buzz noise.

 

So that's where I am now!

[TZJB]

8 minutes ago, psykix said:

Thanks for the input. I should probably clarify the order of events, since I seem to have thrown some red herrings into the mix along the way. It's been a bit of a learning curve for me!

 

I got the Atari 800XL and 1050 out of the parents loft. Initially everything appeared to work fine, and I managed to load the first floppy disk that I tried. I went to load a 2nd disk and the 1050 appeared to have stopped working. I ended up replacing the 47uf caps in the 1050 and that appeared to come back to life. At least the drive motor was working again and the activity light was also behaving as it should.

 

I then went to try loading another disk and got a load of Boot Error messages scrolling down the screen. It was only later that I realised that I had the cable in the wrong port on the back of the 1050 which may have accounted for those errors.

 

I then tried a joystick and Star Raiders cartridge. The Atari booted to what I now know to be self diagnostics but I didn't realise at the time that the Star Raiders cartridge had self diagnostics on board.

 

I removed the cartridge and powered up the 800XL normally and this time it just went to blue screen and white cursor, and that's where I am at currently. Trying Star Raiders again, other than the first time just gave a black screen. Now however, it does nothing and the 800XL just stays on blue screen white cursor.

 

RE: the power LED.. this is a little embarrassing.. pin 24 on the ribbon cable had broken where it connects to the keyboard. I've repaired that with a little bit of kynar wire and have a working LED now.

 

Holding Option whilst booting does nothing. Holding Start whilst booting gives the buzz noise.

 

So that's where I am now!

 

Both ports on an Atari 1050 disk drive are connected internally so either can be used. Boot error usually means there is communication.

 

It sounds like your Star Raiders cartridge may have a fault as it should not bring up the internal self-test which is part of the internal operating system ROM.

 

This may have caused your OS ROM to smoke in this instance which might cause the 6520 pins D1-D5 28-32 to be low as they will be low on any chip on the DATA bus.

 

Further, I just checked an R6520 in a RamboXL machine and there are some discepancies with yours.

 

Both pin 11 and pin 19 should have pullup resistors and should be around the supply voltage level.

 

Here are the voltages I have pulled from my R6520 with a supply voltage of 4.95V, but disregard pins 12-17 due to RamboXL and the 800XL entering the self-test mode indicated by pin 17 low.

 

1 0.06V

2-9 4.86V

10 4.90V

11 4.90V

12 5.02V

13 5.08V

14 5.08V

15 4.92V

16 5.09V

17 0.178V

18-20 4.90V

21 3.72V

22 4.90V

23 4.73V

24 4.90V

25 1.776V

26 2.735V

27 1.944V

28 2.220V

29 2.358V

30 2.704V

31 1.691V

32 1.188V

33 0.572V

34 4.68V

35 3.59V

36 3.71V

37 4.91V

38 4.91V

39 4.86V

40 4.90V

 

I hope this may help.

 

 

[Beeblebrox]

Glad u sorted the power light. I've been there before. 

 

I would certainly focus on the pia at the mo. Rule that or it's socket, vias, etc. 

 

One other thing. Can I just check that at no stage have you plugged or unplugged the SIO cable whilst the Atari and or the drive has been powered on? They must always both be powered off. I've fried chips on the 1050 drive plugging and unplugging the SIO whist the drive was on. 

[psykix]

I do think it probably coincided with plugging the Star Raiders cart in tbh.

 

I'll go and have another look later or in the morning. I think I have an EEPROM programmer somewhere that is still new in the box from about 10 years ago if programming a replacement OS ROM is a thing?

 

I can't honestly say hand on heart that I haven't plugged or unplugged the SIO cable with anything powered on. I'd like to say I haven't but... /shrug

 

[Beeblebrox]

33 minutes ago, psykix said:

I do think it probably coincided with plugging the Star Raiders cart in tbh.

 

I'll go and have another look later or in the morning. I think I have an EEPROM programmer somewhere that is still new in the box from about 10 years ago if programming a replacement OS ROM is a thing?

 

I can't honestly say hand on heart that I haven't plugged or unplugged the SIO cable with anything powered on. I'd like to say I haven't but... /shrug

 

Sure. 

If you need an os Rom chip or mmu I have loads. Happy to post to you for free if you cover postage. £1.99 should cover it. I've some spare antistatic bags and mini cardboard boxes. 

[TZJB]

19 minutes ago, psykix said:

I do think it probably coincided with plugging the Star Raiders cart in tbh.

 

I'll go and have another look later or in the morning. I think I have an EEPROM programmer somewhere that is still new in the box from about 10 years ago if programming a replacement OS ROM is a thing?

 

I can't honestly say hand on heart that I haven't plugged or unplugged the SIO cable with anything powered on. I'd like to say I haven't but... /shrug

 

 

I imagined as such. Star raiders is probably toast too.

 

You may well be able to program an EPROM with the OS depending on your programmer. Anything similar to 28 pin 27128, 27256 or 27512 or EEPROM variants will work.

 

The ROM image is 16KB so will fit on any of those. With the latter two, just move the data to the end of the ROM space for the Atari to be able to access the ROM data without modifications.

 

A 800XL will need the XL/XE OS Rev.2, or Rev.3 which is available here:-

 

 

[psykix]

37 minutes ago, Beeblebrox said:

Sure. 

If you need an os Rom chip or mmu I have loads. Happy to post to you for free if you cover postage. £1.99 should cover it. I've some spare antistatic bags and mini cardboard boxes. 

That's extremely generous of you! I'll drop you a PM.

[flashjazzcat]

I just fixed the 'Black screen' 800XL from another thread and the repair was too trivial to charge money for, so if you get nowhere with this one and are in the UK, drop me a message.

[+kheller2]

The 1050 probably isn't loading anything anymore because  U1 LM3086 is fried (Easily happens) or the heads are dirty from reading your old disks (often happens).

Make sure your cartridge socket teeth are not bent and shorting.

You should be able to get into diags with option, that button goes right to the GTIA. Ground pin 12 of the GTIA should do the same thing.

Part of me thinks the BASIC ROM is toast. You could remove that, and it should boot w/o it.

Remember to give time during power cycles, at least 5 seconds.

If you can turn it on now with start down and hear the buzz, that at least signals part of the OS is still working.

Turn on the 1050, then the 800XL, do you still get boot errors? - again signs the OS is working.

 

StarRaiders doesn't have any diagnostic code (the self test is in the OS ROM).  Star Raiders is considered a "diagnostic cartridge" because it has bit set in its own ROM (the diagnostic cart bit) that bypasses much of the OS initialization.  SALT probably does too (but I'm not sure).

 

 

 

 

[psykix]

Cartridge socket teeth looked fine to me - the SALT works fine in it.

 

Option doesn't work.

 

Removed BASIC ROM - exactly the same blue screen white cursor.

 

No boot errors any more. The activity light comes on and I hear the drive motor going and then it just seems to keep going until I power the 1050 off.

 

I have dug out my unopened universal programmer. If I want to try to read the OS ROM any idea what I can select as the chip in the programmer? There's a massive list and this seems to be a Symbios Semiconductors which isn't in the list.