130 XE - No Video Output / Boot Up

[xrbrevin]

its not unheard of for a freddie to fail - i needed to replace the one in my 130xe

[BeaglzNZ]

 

So check the Freddie chip in another motherboard, probably it is dead Freddie which is common damage.

By the way I told you past before, there is a clock problem if you have no reaction on video output at all.

 

 

Thanks for that - my working 130XE doesn't have the Freddie chip socketed so a bit of surgery required if I am to attempt to swap them.

Still learning about checking for the Clock signals - a lot of the suggestions have been around 'check for clock signal' but no real tips on how to actually do this and what readings to expect - all part of the fun of 'learning on the fly'.

Cheers.

[+DrVenkman]

 

Thanks for that - my working 130XE doesn't have the Freddie chip socketed so a bit of surgery required if I am to attempt to swap them.

Still learning about checking for the Clock signals - a lot of the suggestions have been around 'check for clock signal' but no real tips on how to actually do this and what readings to expect - all part of the fun of 'learning on the fly'.

Cheers.

 

Do you have an oscilloscope? If so, check pin 28 of the GTIA first. That's the system clock (NTSC or PAL) input into the computer and sets the overall timing for everything. If you're getting the right signal there, next check the clock input (Phi0) into SALLY at pin 37, and the two clock outputs (Phi1 and Phi2) from SALLY at pins (3 and 39 respectively). Phi2, in particular, sets the basic pulse of almost everything else in the Atari.

 

If you get a Phi2 signal at pin 39 of SALLY, next check the same signal at pin 7 of POKEY, pin 29 of ANTIC, and pin 25 of the 6520 PIA. The signals at POKEY, ANTIC and PIA should appear sharper and somewhat better defined than the raw signals off SALLY because they go through some buffering circuitry to try to create a sharper square-wave pulse.

 

If you don't have an oscilloscope, you can still check for clock pulses (though not measure them) with a <$20 logic probe. You should get fast pulses at all the pins I mention above.

[BeaglzNZ]

 

Do you have an oscilloscope? If so, check pin 28 of the GTIA first. That's the system clock (NTSC or PAL) input into the computer and sets the overall timing for everything. If you're getting the right signal there, next check the clock input (Phi0) into SALLY at pin 37, and the two clock outputs (Phi1 and Phi2) from SALLY at pins (3 and 39 respectively). Phi2, in particular, sets the basic pulse of almost everything else in the Atari.

 

If you get a Phi2 signal at pin 39 of SALLY, next check the same signal at pin 7 of POKEY, pin 29 of ANTIC, and pin 25 of the 6520 PIA. The signals at POKEY, ANTIC and PIA should appear sharper and somewhat better defined than the raw signals off SALLY because they go through some buffering circuitry to try to create a sharper square-wave pulse.

 

If you don't have an oscilloscope, you can still check for clock pulses (though not measure them) with a <$20 logic probe. You should get fast pulses at all the pins I mention above.

 

Thanks for the above - I don't have an oscilloscope but do have a logic probe. Have set it on TTL and connected to 5v and ground. Not getting Pulse signals - only high or low. Getting nothing on Pin 29 apart from a brief single pulse on ANTIC. Looking at the main ICs looks like the previous owner has done some work and damaged some pins. Will go back to the start and swap the ICs into my known working computer and see what happens.

Just about getting to the stage of selling as a 'repair project'!

[BeaglzNZ]

OK - so the progress today:

 

• Removed CPU, Antic, GTIA, PIA & Pokey and tested in my 800XL (equivalent ICs were already socketed) - They all appear to be working as in the computer booted up.
• De-soldered my Freddie IC from working 130 XE and installed a 40 pin socket - now that computer is reporting 8 bad memory chips - great!
• Put the Freddie from the 'dodgy' computer into working computer and no life.
• Put known working Freddie into 'dodgy' computer and now get a black screen - secondary problem somewhere. Interestingly the Sys-Check isn't initialising with the this configuration.

 

Progress of sorts today although now have a lot of memory chips to de-solder from the PCB - got a load of 41645 arriving Tuesday all going well, hope I ordered enough for 2 computers! Off to order a couple of Freddie chips and keyboard membrane as well.

[+DrVenkman]

OK - so the progress today:

 

 

• Removed CPU, Antic, GTIA, PIA & Pokey and tested in my 800XL (equivalent ICs were already socketed) - They all appear to be working as in the computer booted up.
• De-soldered my Freddie IC from working 130 XE and installed a 40 pin socket - now that computer is reporting 8 bad memory chips - great!
• Put the Freddie from the 'dodgy' computer into working computer and no life.
• Put known working Freddie into 'dodgy' computer and now get a black screen - secondary problem somewhere. Interestingly the Sys-Check isn't initialising with the this configuration.

Progress of sorts today although now have a lot of memory chips to de-solder from the PCB - got a load of 41645 arriving Tuesday all going well, hope I ordered enough for 2 computers! Off to order a couple of Freddie chips and keyboard membrane as well.

That would concern me. Before you do much else, at least verify continuity for every pin on your newly-socketed machine to the next component in line. You may well have damaged a pad or trace during your removal-and-socket procedure on that box. If youve damaged a FREDDIE connection, that will affect the validity of the test results. Edited April 28, 2019 by DrVenkman

[BeaglzNZ]

That would concern me. Before you do much else, at least verify continuity for every pin on your newly-socketed machine to the next component in line. You may well have damaged a pad or trace during your removal-and-socket procedure on that box. If youve damaged a FREDDIE connection, that will affect the validity of the test results.

 

Yep - double checked the continuity of the 40 pin socket and everything is good. No shorts either between pads.

Will have another closer look at it next weekend.

[apolkosnik]

I'm in a similar boat with 65xe, when I turn it on, I get black screen. Pressing reset button results in a little audible "pings".

I've added a socket under Sally (CPU) and it tested ok after transplanting in a perfectly good XL.

I tried a few game cartridges, nothing worked except Star Raiders. It actually uses the debug mode and it starts before the system. It's actually quite playable, and sound, graphics, joystick, and keyboard work.

I've added sockets under all memory chips, and I've got new ones arriving in a week just so that I can test them.

Star Raiders' sounds of engines, shots, explosions, alarms, etc. are algorithmically synthesized directly using the Atari POKEY sound chip's capabilities.

Just in case I've ordered a replacement OS chip. I'm not sure how to test FREDDIE other than with maybe SALT cartridge.

I was thinking to try the Ultimate cart, if it also can work as debug mode cart. Thanks!

[BeaglzNZ]

Still trying to track down the culprit with this 130 XE.

 

I have dropped in a new Freddie and that seemed to improve things - I now get some form of video output although it could be a black or red screen depending on how the pot trimmer on the motherboard is adjusted.

 

The Sys Check board still doesn't do anything on this computer so I dropped in a new ROM and that did nothing different. Have tried the CPU in a different computer and it works fine.

 

Found 1 damaged track on the underside and have fixed that but again no difference. Cannot see any other damaged tracks.

 

Swapped the MMU into a working machine and it worked fine.

 

Did a continuity check from the pins on the CPU socket and they are all good.

 

Just dropped a new ANTIC in and now getting some improved results - in fact, I think it is now cured! Just need to install new keyboard membrane. Memory test is all good as well!

 

Another one is brought back to life!

[xrbrevin]

congratz! tenacity will win through in the end!