Help w/ 800XL and 600XL

[unixdude]

Hey Atari people!

 

A while ago, I bought an 800XL that turned out to be dead: it started up to a black screen.  In my troubleshooting process, I desoldered the OS chip, and probably destroyed it but I'm not sure.  In any case, the pins are dirty and bent, and I don't want to install it into the socket that I installed in its place.

 

This week, I checked the 800XL with a Sys-Check, and it identified a dead RAM chip.  I desoldered that and then installed a socket in its place and inserted a new RAM chip.  After that, the 800XL passed all Sys-Check tests with the 600XL's known good OS chip.  I was then able to play some cartridge games.

 

Maybe this was stupid, but I left the unit powered up.  When I returned to it a while later, I discovered a black screen and a strange smell.  Since then, the 800XL always boots to a blank screen, maybe a dark olive green color, even with the Sys-Check installed.  It doesn't matter which OS the Sys-Check is set to boot, it's always this blank, dark screen.

 

Also, my 600XL will no longer boot with this OS chip: it boots to black screen when I use the XL/XE OS chip.  Basically, the 600XL now does the same thing the 800XL does, if using the original Atari XL/XE OS chip.  (Using the Sys-Check in the 600XL has slightly different results, keep reading.)

 

Because of all of this, I suspect I might have killed the OS chip.  But, there's more: using the XL/XE OS in the Sys-Check, the 600XL starts by showing the normal blue screen with cursor, then it always switches to the self-test.  Unfortunately it's my only XL/XE OS chip, so I need to buy another two now... maybe I'll buy three.

 

Any thoughts about how to revive these systems?  I'd hope that an OS chip would revive the 600XL, but since it won't boot using the Sys-Check's XL/XE OS, I'm not sure what to think about that.  The 600XL boots the Sys-Check OS just fine, and of course it fails the RAM test.  It boots the QMEG OS, and the two XL/XE OSes always boot to self test.  I've googled for it and haven't figured out what makes an XL boot to self-test without any keys pressed.  Anybody here know why that would be?

 

For the 800XL, I'm suspecting it will require more surgery: maybe it will require the removal and replacement of of more (all?) RAM chips. Of course, I'll socket those rather than soldering the new chips.

 

Any and all help appreciated.

Edited March 5, 2020 by unixdude
To give more details about the 600XL boot

[JR>]

Does your power supply look like the one circled below?  If so, it could be damaging your systems.  When it fails it may output destructive voltage levels.

 

[unixdude]

No, I cut the end off of that one.  Mine looks like the huge black brick in the bottom left corner -- I bought it from Best.

[+Nezgar]

35 minutes ago, unixdude said:

No, I cut the end off of that one.  Mine looks like the huge black brick in the bottom left corner -- I bought it from Best.

Ok good. Now that we have ruled out the power supply that fails with a high voltage, I wonder if yours is failing with a low voltage? I have the left white power supply, and it had a 7805 voltage regulator that would drop voltage randomly, until I replaced that component... does it work OK on the other computer?

 

Check the voltage from the PSU unloaded, and then with the computer on - you can measure it from a joystick port, both ground and +5V are available there.

[MrFSL]

i had power supply issues and got a nice bit of kit to help me out. Like many people I have a whole bin full of old power supplies from various devices like old laptops and similar - none of which was 5V. I ended up spending $2 USD on a DC-DC converter. Then I grabbed an old high powered laptop power supply and wired them together. This link is similar to the one I bought (I bought a small quantity and got a much better discount though.)

 

https://www.amazon.com/watersouprty-Voltage-Regulator-Switching-Converter/dp/B07WFNW18Z

 

They make all types - some have nifty display panels, pre-soldered usb ports --- some convert down --- others convert up. My point is for two dollars its a nice piece of reusable kit that allows me the ability to use many different power sources I have laying around and get some additional protection as well.

 

https://www.amazon.com/s?k=DC+to+DC+Buck+converter&s=price-asc-rank

 

Personally I might purchase one with a LED in the future just for extra geek points. This one look neat enough:

 

https://www.amazon.com/DROK-Converter-5-3V-32V-Regulator-Transformer/dp/B078Q1624B

 

[+DrVenkman]

That weird smell you mentioned makes me wonder if one of the small electrolytic caps inside got hit with some heat by accident, or a solder bridge shorted one of them out. Inspect them all really closely, ideally under light and magnification, for any leakage or swelling. 

[xrbrevin]

you can create your own OS ROM chip if you have an EPROM burner

[unixdude]

4 hours ago, xrbrevin said:

you can create your own OS ROM chip if you have an EPROM burner

This sounds really interesting. I need to learn about this. Any suggestions on a good burner and good source of chips?

[unixdude]

11 hours ago, DrVenkman said:

That weird smell you mentioned makes me wonder if one of the small electrolytic caps inside got hit with some heat by accident, or a solder bridge shorted one of them out. Inspect them all really closely, ideally under light and magnification, for any leakage or swelling. 

Maybe so.  When you say "small electrolytic caps," do you mean the tiny ones next to the RAM, like C37?  Or do you mean other ones, like C22?  I assume you mean the ones next to the RAM -- C34-C41.  Thanks!

[unixdude]

11 hours ago, Nezgar said:

Ok good. Now that we have ruled out the power supply that fails with a high voltage, I wonder if yours is failing with a low voltage? I have the left white power supply, and it had a 7805 voltage regulator that would drop voltage randomly, until I replaced that component... does it work OK on the other computer?

 

Check the voltage from the PSU unloaded, and then with the computer on - you can measure it from a joystick port, both ground and +5V are available there.

It's possible I guess, I'm not super familiar with all of this.  I have the 2 XLs, but I also have an XEGS which I believe takes the same PS. I guess I could plug that up.

 

Prior to this week, the PS worked just fine on the 600XL.  As of now, the 600XL boots into Sys-Check, but it fails the RAM test of course (it isn't upgraded).  The 600XL boots to self-test if I use the Sys-Check as an OS switcher with the OS set to XL/XE OS.  The 600XL boots to black screen if I boot without the Sys-Check connected.

[xrbrevin]

The MiniPro TL866A is cheap and will serve 99% of your needs. I have one and havent been disappointed yet.

Many other members on here have the same and there is modded firmware available too ?

I get chips from ebay - they uber cheap if youre prepared to wait for a china delivery otherwise they are still good value if bought locally

[mimo]

don't forget to add a UV eraser , cheap ones are fine

 

https://www.ebay.co.uk/itm/ltraviolet-UV-EPROM-Eraser-Erase-Eraseable-Timer-110-240V-6/163690392062?hash=item261cb529fe:g:p9cAAOSwM-Zcz9-e

[SS]

52 minutes ago, unixdude said:

I have the 2 XLs, but I also have an XEGS which I believe takes the same PS.

The XEGS power supply is 5V 1A.  A XL requires a minimum of 5V 1.5A.  If you use a XEGS power supply on a XL machine, you are not getting enough amperage.  The reverse is OK though, it is perfectly fine to use a 1.5A PS on a XEGS machine. 

[unixdude]

50 minutes ago, xrbrevin said:

The MiniPro TL866A is cheap and will serve 99% of your needs. I have one and havent been disappointed yet.

Many other members on here have the same and there is modded firmware available too ?

Is the TL866II or Plus also a good choice? I’m on a Mac so I need something that will work with flashrom. Happy to try the TL866 if I can find a good one. Amazon has newer units, but I do see some 866A models on eBay. 
 

This could really be fun, getting into OS switching and trying out new OSes. 
 

Thanks!

 

And thanks to mimo for the suggestion about the eraser. I’ll definitely add that if I get a burner. 

[+DrVenkman]

1 hour ago, unixdude said:

Maybe so.  When you say "small electrolytic caps," do you mean the tiny ones next to the RAM, like C37?  Or do you mean other ones, like C22?  I assume you mean the ones next to the RAM -- C34-C41.  Thanks!

The tiny ones are usually ceramic and they very, very rarely go bad. The electrolytics on an Atari are usually the blue, cylindrical ones, with a white bar or stripe on side indicating polarity. You can inspect them under magnification to see if they’ve split, are bulging or seeping. 

 

But it would really help to see pics of the work done to see if experience eyes can spot anything else obvious.

[unixdude]

Okay, here are some pics. Usually I wouldn't post full-size pics, but that full resolution might be helpful here.  The work area was only the one chip -- desolder, then solder socket in place, and we had to add some traces because we broke a trace on the top side.  The other pics show the entire board, mostly so you can see the capacitors.

[unixdude]

Sorry that I forgot to rotate the motherboard pic.  Also, I just noticed that I replaced a 4264 with a 4164. Is that a problem?

[_The Doctor__]

that chip you've put in is 100 refresh rate chip instead of 150...

https://html.alldatasheet.com/html-pdf/102234/SAMSUNG/KM4164B-10/297/1/KM4164B-10.html

depending on the antic chip in the atari and how picky this page mode samsung chip is you might do better to pick a NEC chip etc at 150 or 120 etc...

the 600xl uses a different chip entirely btw....

 

double check your work and the voltages coming from the power supply, mt chip die often, I normally replace all mt memory chips once a bad one occurs...

Edited March 14, 2020 by _The Doctor__

[tane]

On 3/5/2020 at 2:56 PM, unixdude said:

Sorry that I forgot to rotate the motherboard pic.  Also, I just noticed that I replaced a 4264 with a 4164. Is that a problem?

 

10 hours ago, _The Doctor__ said:

that chip you've put in is 100 refresh rate chip instead of 150...

https://html.alldatasheet.com/html-pdf/102234/SAMSUNG/KM4164B-10/297/1/KM4164B-10.html

depending on the antic chip in the atari and how picky this page mode samsung chip is you might do better to pick a NEC chip etc at 150 or 120 etc...

the 600xl uses a different chip entirely btw....

 

double check your work and the voltages coming from the power supply, mt chip die often, I normally replace all mt memory chips once a bad one occurs...

 

The KM4164B-10 works good on 130XE, but not with 65XE and 800XL, even if you change all 8 chips. If you insert a KM4164B-10 in those systems, immediately it will heat up uncontrollably. For some reason, then if you replace the chips with the original ones, in some cases it won't work at the first time. But it doesn't mean that there is something damaged. You have to rotate them until it works.

 

You need a new RAM model.

 

This blog suggests to replace the chips with KM4164B-15 for a 800XL / 65XE.

 

However I'm confused. This post says that a 130XE with Antic C021697 requires a RAM with 256 cycle refresh or 4ms, and a 65XE & 800XL with Antic C012296 requires a RAM with 128 cycle refresh or 2ms. According to the KM4164B Datasheet, such model has a 128 cycle refresh, for all speeds KM4164B-10 and KM4164B-15 (100ns & 150ns). But I have tested that KM4164B-10 works with 130XE but not with 65XE.

 

Is there a table with RAM models and systems compatibility?

What is the best and fast RAM replacement for a 65XE?

What's the difference between 4164 and 4264 models? There is also a 41256 model.

 

Edited March 14, 2020 by tane

[Rybags]

The suffix isn't refresh it's access time.

An old Ram expansion article for the 400 mentioned 250 ns as being the maximum that would work, which equates to just under half a cycle which makes sense.

 

Required refresh rate for probably any chip you find to suit XL/XE will probably be close to double the time the Atari takes to do it.

When the chipset was designed they chose 9 cycles per scanline, later machines like C64 and Plus4 only use 5 as the DRams of the later time needed refreshing less often.

 

If you check pictures of XLs and XEs you'll notice they use DRams with access times usually in the 100-150 ns range.

I'm fairly sure I've even used ones with 90.  In theory there shouldn't be a minimum that upsets things, I don't think the DIP form factor had much under 70 in common use, by the mid 90s the smaller form factor ICs were dominant and usually mounted on SIMMs.

 

Referring to complete refreshes - 1 ms equates to just under 16 scanlines in PAL (which has slightly lower line rate than NTSC).

In a general worst-case scenario (which isn't the worst possible) with 2 badlines in Gr. 0 you should get 128 refresh cycles in that time, so close to double of what might be expected.

Edited March 14, 2020 by Rybags

[ClausB]

41xxx was a standard part number for bit-wide dynamic RAM. Some manufacturers used 42 or 81 or other numbers. Some had extra features that Ataris didn't need.

 

The xxx gives the size in K bits:

4116: 16 Kb

4164: 64 Kb

41256: 256 Kb

 

All these came in 16-pin DIPs with 13 pins compatible, making upgrades fairly easy.

[tane]

Fill the table with your RAM chips:

 

 

  

                        |   130XE   | 65XE / 800XE |  1200XL  |   800XL  |  600XL  |   800  |  400

-----------------|------------|------------------|-------- ----|-----------|-----------|--------|---------
KM4164B-10    |   Works    |          No           |                  |               |               |            |

MT4264-15      |                 |                         |                  |  Works   |               |            |

. . .                   |                 |                         |                  |               |               |            |

                        |                 |                         |                  |               |               |            |

                        |                 |                         |                  |               |               |            |

 

 

[+Nezgar]

The 42xx denotes that it has a page mode feature over the 41xx DRAM's. Page mode is not used by the Atari 8-bits, so both types will work. (Aside from access time)

 

And as far as the ANTIC variants go, if I have my notes right:

• C012296 (older) has a 7 bit refresh counter and works only with (older) DRAM with 128 cycle refresh. (2ms)
• C021697 (newer) has an 8 bit refresh counter and works with DRAM with both 128 & 256 cycle refresh. (4ms)

[ClausB]

Yep, but as Rybags said, ANTIC refreshes in about half that time.

 

 

Edited March 15, 2020 by ClausB

[R.Cade]

I see you still have Micron RAM on that board (MT). In my experience, those are almost always failed or failing.

 

Do I understand that this 800XL passes the self-RAM test (all green) but then still only boots back to the self test? If that's the case, then it could be a ROM problem or maybe possibly the MMU PAL/GAL.

 

Edited March 15, 2020 by R.Cade