OJ's H5 A3 Troubleshooting

Share your building progress here!
Post Reply
User avatar
olivier.jan
Posts: 9
Joined: Mon Jun 01, 2020 8:00 am

OJ's H5 A3 Troubleshooting

Post by olivier.jan » Sat Nov 21, 2020 9:57 pm

Hi everyone,
As I wanted to get my A3 running before the B1 starts popping-up, I rushed the build this week and ended with a beautiful...black screen.
After checking a bit, I realised that IC6 was not properly re-soldered which I fixed and got a beautiful.. white screen.
Some more checks later, I got proof that beer and soldering together are not a good idea cause you end up with a CPU socket at 90º :oops:
Once the socket was re-soldered in the right position I finally got a ... white screen :(
Strangely, while display the white screen, my monitor tells me it's NTSC, not the usual PAL I get with my STF or STE...

I tested voltage everywhere and for shorts on all extensions slots pins, clock frequencies on all the ICs, and everything looks OK so far.
Latest troubleshooting today shows there's activity but it execute a few instruction, reset, execute instructions, reset, etc...

I've tested CPU, MMU and GLUE in another machine and all are good, so maybe the ROM as I have no way to test it (AT27C4096-55, with 1.04 and EMUTOS, both gives me a blank screen).

I ordered a new ROM and drag cart from Exxos today in order to do more troubleshooting (hopefully) next week. :)
In the meantime, if anyone has an idea for further troubleshooting, here are a picture of the board and 2 dumps of the first cycles after reset...
IMG_5781.jpg
IMG_5781.jpg (572.34 KiB) Viewed 120 times
Capture d’écran 2020-11-21 à 16.17.33.png
Capture d’écran 2020-11-21 à 16.17.33.png (136.58 KiB) Viewed 120 times
Capture d’écran 2020-11-21 à 16.23.05.png
Capture d’écran 2020-11-21 à 16.23.05.png (111.3 KiB) Viewed 120 times

stephen_usher
Trusted Guru
Trusted Guru
Posts: 1108
Joined: Mon Nov 13, 2017 7:19 pm
Location: Oxford, UK.
Contact:

Re: OJ's H5 A3 Troubleshooting

Post by stephen_usher » Sat Nov 21, 2020 10:13 pm

It's unlikely to be the ROM. Hopefully the Diag cart will help, especially with a terminal on the serial port.

The display will be "NTSC" until the ROM has managed to change the setting during the initialisation process.

It looks like it's reading the first few bytes of the ROM and then crashing. This could be not reading the ROM properly or not accessing RAM. Seeing as you aren't seeing what's on the other 8 data lines it's hard to see if any of those aren't working.

I've not verified the contents of those first few bytes of ROM, which should include the address of the base of the ROM.

You'd better check that all the address lines are busy.
Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.

User avatar
PhilC
Moderator
Moderator
Posts: 3780
Joined: Fri Mar 23, 2018 8:22 pm

Re: OJ's H5 A3 Troubleshooting

Post by PhilC » Sat Nov 21, 2020 10:30 pm

Are you saying that the H5 is resetting itself or are you resetting it? Recoding /halt is a better guide than /reset by the way.

One thing to check is to remove the CPU and check that the address and data lines are pulled up to 5v, same for R/W, BGACK, BERR etc. Its also worth checking this on the DMA and other chips to eliminate bad soldered joints.

Good luck.
If it ain't broke, test it to Destruction.

User avatar
Icky
Moderator
Moderator
Posts: 2602
Joined: Sun Sep 03, 2017 10:57 am
Location: UK
YouTube: https://tinyurl.com/yals4a3k
Contact:

Re: OJ's H5 A3 Troubleshooting

Post by Icky » Sat Nov 21, 2020 10:47 pm

@olivier.jan - Looking at your board JP13 is missing. You need to make sure that one is closed. This is the ROM_CE line so would explain why its not seeing the ROM

User avatar
olivier.jan
Posts: 9
Joined: Mon Jun 01, 2020 8:00 am

Re: OJ's H5 A3 Troubleshooting

Post by olivier.jan » Sat Nov 21, 2020 11:12 pm

Thanks for your replies.

Concerning JP13, it was actually plugged during my tests and got off when I removed the analyzer cables to take the picture.
I also checked all address pins and all data pins to try to spot the issue, but they’re all connected and have activity.
Tomorrow I will run some more tests, checking all the pull-ups as advised and again the data pins bit with UDS and LDS and a few other signals too.
I was reviewing the bytes captured and the sequence match the first few bytes of the rom, whic is strange as it should match only one out of two as I m only recording d0-d8...

I will also solder the cart port and serial, it will make using the diag cart a bit easier.

User avatar
exxos
Site Admin
Site Admin
Posts: 12604
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
YouTube: https://www.youtube.com/user/exxosuk
Contact:

Re: OJ's H5 A3 Troubleshooting

Post by exxos » Sat Nov 21, 2020 11:18 pm

Have a look here as well viewtopic.php?f=78&t=2362
https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.

Post Reply

Return to “H5 A3 USER BUILDS”