Hi,

My 600XL will freeze 5 min after power up pointing most probably to a chip overheat. Leaving it turned on will then give a garbled screen with colored text in graphic 1/2 mode.
Unfortunately replacing the ANTIC did not solve the problem and I still have this weird video crash some minutes after power up (see pictures). I have then tried also to replace the GTIA but no changes. Tried also to replace both rams with 2 fresh new ones and no changes also.
Now what I can tell is that the problem has evolved a little bit. After the first crash (when the faulty chip is probably overheated), I cannot load a game with the OPTION key pressed to bypass the BASIC but I get a black screen. If I recycle the machine without the Option key pressed then I boot into Basic but will have the crash sooner or later. I have tried to cool down a TTL marked C061618 in U2 which is quiet hot compared too other but no changes. I have a freezing spray to test in case someone can point me chips to test.

2 things :

Either the CPU or PIA or POKEY is gone and I will know when I will get the replacements soon (thanks Rewindgames ) or either a TLL is faulty somewhere or finally this has nothing to do with a Chip but another component such as a capacitor or transistor or whatever which is gonna be a pain to find out.

Thanks

Hello,

Most likely it's the CPU.
And then the freeze spray will help, if cold it will work.

BR/
Guus

Hi Guus

Many thanks for your reply . I am waiting for a spare CPU and will see. I remember having cooled the CPU when trying to troubleshoot the machine but had still the crash (I remember though that the machine ran longer than before). Then I focused on the ANTIC and cooling it has extended the time a lot so I was suspecting logically this one but this is not the case. Maybe a simple coincidence

I will swap CPU and revert.

Thanks
Rick

Hi Guus

Sorry first post had a lot of typo errors and not very clear (do not know how to edit so I repost here)
***************************************************************

Many thanks for your reply . I am waiting for a spare CPU and will see result. I remember having cooled the CPU when trying to troubleshoot the machine and this had stopped the crash for a few moment (I remember that the machine ran longer than before but then crashed even when cooling the CPU). Then I focused on the ANTIC and cooling it has extended the time a lot so I was suspecting logically this one but this is not the case. Maybe a simple coincidence

I will swap CPU and revert.

Thanks
Rick

Hi Guys,

Ok I am back but not good news except that now I have a whole set of chips for spare . So I have swapped RAMS/ANTIC/GTIA/CPU/PIA and POKEY with no success. So I was really looking in the wrong direction. As Brenski said the problem is somewhere else now. I would exclude BASIC and OS ROMS as they do pass the TEST. Capacitors or transistors I do not think they give this weird video freeze. Now having said that I have a complete random behave of the machine. Sometimes I have a black screen at power up with OPTION pressed, sometimes it is a red screen and most of the time it will boot but crash miserably after a few minutes. I am testing with the case opened of course, I noticed that the power led sometimes blinks intermittently, when I push on the keyboard case to reseat it the led will light up and sometimes it will go off (bad contact?). I have also tried to push and move the power DIN connector and had a couple of freeze but now I do not know if this is a coincidence or if there is a problem there.
As Brenski from Atari Sector suggested, it could be in fact a bad solder joint somewhere or the PSU not delivering the correct power. Can I test with a standard PSU? how much is the voltage? 5v 1,5 Ampers?

Garbage on screen will appear a couple of minutes after the crash and the whole thing rolls rapidly up and down.

Hi again,

I have noticed the MMU is getting hot really quick and it is the hottest chip on the board. As far as I understood it has a function for video management so this can be at fault.
Marked C061618

Hi,

Pacman74 hat geschrieben:As Brenski from Atari Sector suggested, it could be in fact a bad solder joint somewhere or the PSU not delivering the correct power. Can I test with a standard PSU? how much is the voltage? 5v 1,5 Ampers?

Garbage on screen will appear a couple of minutes after the crash and the whole thing rolls rapidly up and down.

Yes, 5 volts. You need at least 1A, the 600XL without heavy expansions draws about 800 mA max.

You should analyze the timing relevant parts with a scope. If major part changement (CPU, ANTIC etc.) doesn´t help, then I would go on with checking the RAS, CAS lines, all parts around the 74LS375, 74LS51 parts and the delay line (CO64072). Some times I already had defective delay lines, so it´s worth a try.

Good luck, Jurgen

Hi,

Pacman74 hat geschrieben:I have noticed the MMU is getting hot really quick and it is the hottest chip on the board. As far as I understood it has a function for video management so this can be at fault.
Marked C061618

What´s the surface (top side) of this chip made of? If it´s a ceramic version, then this is a very old PAL and it´s normal. Also you should cross-check this chip with a well working one.

Jurgen

Hi Jurgen,

Yes the MMU has a white layer between the top surface and legs so I assume it is the ceramic version.
Well I will swap it if possible to check but if high temp fir ceramic IC's are common then chances are it is not faulty.
The PSU is checked and giving correct output +5v. The PSU is not part of the bad PSU series which could easily damage the computer.
All major chips have been swapped rams/GTIA/antic/PIA/pokey and CPU and no changes so all have to be considered as working and not part of the problem.
Still have to test the series of TLL's as you said. Problem may come from there.
Note that the 600xl is modded to 64k but was working good for days before starting to crash.

Hi Rick,

Pacman74 hat geschrieben:Yes the MMU has a white layer between the top surface and legs so I assume it is the ceramic version. Well I will swap it if possible to check but if high temp fir ceramic IC's are common then chances are it is not faulty.

Yes, that´s a ceramic one. These type of MMU gets quite warm - but you always should keep your fingertip on it after 5 minutes of operation. If it´s too hot to let the finger on it, then this is not normal - replace it.

Pacman74 hat geschrieben:Still have to test the series of TLL's as you said. Problem may come from there.
Note that the 600xl is modded to 64k but was working good for days before starting to crash.

Aaah, didn´t mention that. Ok, THEN absolutely first way is to take another two pieces of 41464 DRAM.

Which instructions for upgrading you´ve use?

Regards, Jurgen

Hi Jurgen,

I have already swapped the two 41464 rams with two others but no changes (all 4 are brand new rams).

The mod has been done using this tutorial on Atari Age
http://atariage.com/forums/topic/230722 ... hromaluma/

The mod as worked good since the beginning, problem started just a few days later.

EDIT : Sorry the link I sent you is for the S-video mod I did before and working very good.

This is the tutorial I use for the 64K Mod :

http://atariage.com/forums/topic/183694 ... -pictures/

Cheers,

Riccardo

I am doing another test at the moment. I have switched on the 600XL without the keyboard connected. The machine us now running since 40 minutes with the prompt screen changing colors randomly which is the normale safe function for the old CRT screens. At this time it should have already crashed after 10 minutes more or less.
I am wondering if the problems do not come from the keyboard inputs then. What is the controller which decodes the keyboard inputs? are the two ones in U22 and U23? The ceramic is hot yes but I can easily leave my finger on it.

The machine is running now for more than 1h30. I have connected the keyboard and loaded some games with the SIO2SD and all is running perfect!! I am running it without the metal shield inside.
I do not know what to think. The only difference now is that the power led is always off while before it was lighting up and off randomly because maybe of a loose contact.

Hi Jurgen,

Tested the 600Xl again today and running a cartridge for almost 2h.....without any issue
I do not understand what is going on but I may consider the metal shield as the source of the problem. It was probably short-circuiting somewhere maybe on the area where the 64k mod is.

I have to consider the machine back to life now !!

Pacman74 hat geschrieben:Hi Jurgen,

Tested the 600Xl again today and running a cartridge for almost 2h.....without any issue
I do not understand what is going on but I may consider the metal shield as the source of the problem. It was probably short-circuiting somewhere maybe on the area where the 64k mod is.

I have to consider the machine back to life now !!

Glad to read! Another fine example that sometimes the simplest reasons ARE the solution at all

And yes, the issues with instable 600XL is often located at the shields, in most cases the lower shield has some spurious contacts with some pins. This problem must already occur in the factory, in some cases Atari did use some duct tape to prevent having contact of the lower shield with any part of the solder´s side of the PCB.

BR Jurgen

Exactly. When the shield is loose it is very close to a row of resistors on the right low side and I think it may have shorcutted them when moving.

Problem solved!