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About BeaglzNZ

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    Space Invader

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    Auckland, New Zealand
  1. 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!
  2. 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.
  3. 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.
  4. 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'!
  5. 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.
  6. Programmed a GAL16V8 this morning and as far as I know it has programmed fine but no difference to video output. Dug for some more info on the Freddie chip and CLK seems ok on input but not pulsing on output. If it was a memory problem I thought the Sys-Check would bypass this and operate - DIP switches are set to do this.
  7. Yep - Sys_Check works fine on my other 130 XE. Tried monitor output as well as RF output and no signal. Slowly running out of components to check - will try the MMU tomorrow.
  8. Have just tried burning a new OS and that has made no difference either.
  9. Bit of an update (or plea for help rather): My Sys-Check 2.2 finally arrived and have plugged it into the 130 XE and .... no display! Bugger! Checked the 5v wire on the Sys_Check board and the 5v is there so some good news. I have confirmed that the CPU, ANTIC, GITA, PIA & POKEY are all good by swapping them into a working 130 XE. Can look at programming a GAL16V8 to replace MMU? Otherwise de-solder all the RAM and replace?
  10. This sounds interesting however not having any luck with the link. Any chance this can be updated?
  11. Great stuff - so much for trying to save some money this year and not ordering retro stuff!
  12. If I get a Sys-Check II will it run the tests despite no video output - does it run off its own memory so in effect bypassing the computer memory for boot up? Not really keen on spending NZ$100 for something that isn't going to help me. Best Electronics also have a diagnostic cartridge but is limited to the 65/130xe but also tests some other things.
  13. Tried to source some parts from Best Electronics but they have no CO70034 oscillators - bit of a long shot but does anyone have one available or suggest another supplier? Tried using a logic probe on the memory but not 100% sure what I am looking for - have at least confirmed that the 5v supply is good to all chips. Could possibly be the MMU or Freddie chip (5v good as is ground).
  14. So far I have swapped out the CPU, Antic, GTIA, PIA & Pokey with a working 800XL and they all work. Tried piggy backing a memory chip but no difference. Tried to burn a ROM onto a NEX 27128 but kept getting programming errors. No problems reading the blank chip. Tried to read the original OS Rom but again getting 3 pins with errors. Given it has zero video output could it be the MMU? Will look at getting a new 27128 and try programming that as a replacement ROM.
  15. Thanks for the tips so far - just need to get through the working week and have a look at it on the weekend. Cheers.
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