Jump to content
omf

PAL or SECAM BIOS replacement

Recommended Posts

I have in my possession a problematic SECAM board of which i have modified with 5volt ram, and it still does not work. i want to replace the bios chip with a new one on eprom.

 

looking at the guide here: http://console5.com/wiki/Colecovision_BIOS_Replacement it does not help me at all. the guide appears to not cater for the board types i have

 

even my PAL board does not have the same layout as described in the guide

 

both of the boards have similar layouts to the pictures i have attached, does anyone have any info i could use to replace these bios chips with new ones?

 

is there a guide that someone knows of that will describe the procedure for this board layout?

 

 

maybe someone has the pin layout of the bios chip used, i could then cobble something together myself that will work by matching the pins from the eprom etc

 

post-18126-0-96469700-1383089945_thumb.jpg

post-18126-0-39748400-1383089999_thumb.jpg

Share this post


Link to post
Share on other sites

If push comes to shove you can always buzz out the data lines and address lines from the Z80 CPU to the BIOS. At least you'd have a partial pin out to match against then.

Share this post


Link to post
Share on other sites

Don't forget that you will need a PAL BIOS for a PAL machine. I never bothered to check if there are any differences other than the region byte. But if that byte is wrong, some games won't work as intended.

 

Philipp

Share this post


Link to post
Share on other sites

Don't forget that you will need a PAL BIOS for a PAL machine. I never bothered to check if there are any differences other than the region byte. But if that byte is wrong, some games won't work as intended.

 

Philipp

Is there a dumped PAL/Secam bios anywhere?

Share this post


Link to post
Share on other sites

I don't think there is a specific SECAM BIOS. Latest CV sold in France were rebadged and RGB modded German units(you can recognize them by looking for the back sticker; either a French one cover the original one, or there is just the german one.)

And anyway, French units doesn't even output SECAM....

Share this post


Link to post
Share on other sites

I reticently became privilege to some new information which has ultimately led to me being able to remove the bios chip from the dead french colecovision machine in my possession and read the contents with my programmer..

 

the bios was suspect to be bad but now im not so sure this was the problem

 

after extracting the bios i have tried it in ColEm and it works as it should.

 

as there doesnt seem to be a french rgb machine bios out there that i could see and for those of you who would like it, the bios in question is attached.

 

for those of you in the know what do you think of this file?

 

would you say its fine or corrupt

french rgb bios.bin

  • Like 1

Share this post


Link to post
Share on other sites

I reticently became privilege to some new information which has ultimately led to me being able to remove the bios chip from the dead french colecovision machine in my possession and read the contents with my programmer..

 

the bios was suspect to be bad but now im not so sure this was the problem

 

after extracting the bios i have tried it in ColEm and it works as it should.

 

as there doesnt seem to be a french rgb machine bios out there that i could see and for those of you who would like it, the bios in question is attached.

 

for those of you in the know what do you think of this file?

 

would you say its fine or corrupt

 

Your BIOS is in perfect state :) Thanks for dumping it. :thumbsup: I'm sure Ikrananka will be delighted to see this.

 

I've made a comparison of your BIOS with the original USA BIOS and it has these differences:

  • Some unused space ($FF bytes in original) is filled with trash.
  • The $0069 byte contains $32 (so it means an European machine) first time I've seen confirmation of this.
  • The start delay in Colecovision screen is reduced.

BTW, the common procedure to detect faults in Colecovision is this:

  • Check power supply voltage.
  • Check activity in Z80 MREQ/IORQ pins, CLK input.
  • Check decoder 74LS138 for activity in PSG port output (if BIOS is read correctly, it will turn off PSG sound)
  • Check audio output of SN76489 with headphones (if BIOS is read correcly and 74LS138 works, it will be silent at boot-up, otherwise a tone will be heard)
  • Check decoder 74LS138 again for activity in VDP port output (if RAM works correctly, Colecovision will try to init VDP)

If there is activity in VDP port output then you could try a game that starts immediatly with sound and check with headphones. From there you can route and check if VDP chip is damaged or TV output doesn't work.

  • Like 3

Share this post


Link to post
Share on other sites

 

Your BIOS is in perfect state :) Thanks for dumping it. :thumbsup: I'm sure Ikrananka will be delighted to see this.

 

I've made a comparison of your BIOS with the original USA BIOS and it has these differences:

  • Some unused space ($FF bytes in original) is filled with trash.
  • The $0069 byte contains $32 (so it means an European machine) first time I've seen confirmation of this.
  • The start delay in Colecovision screen is reduced.

BTW, the common procedure to detect faults in Colecovision is this:

  • Check power supply voltage.
  • Check activity in Z80 MREQ/IORQ pins, CLK input.
  • Check decoder 74LS138 for activity in PSG port output (if BIOS is read correctly, it will turn off PSG sound)
  • Check audio output of SN76489 with headphones (if BIOS is read correcly and 74LS138 works, it will be silent at boot-up, otherwise a tone will be heard)
  • Check decoder 74LS138 again for activity in VDP port output (if RAM works correctly, Colecovision will try to init VDP)

If there is activity in VDP port output then you could try a game that starts immediatly with sound and check with headphones. From there you can route and check if VDP chip is damaged or TV output doesn't work.

i have just started to look at this again with my new cheap usb logic analyser, i have noticed that the IORQ doesnt really do a great deal, MREQ and CLK seem to produce what i would expect to see. but what i am asking is what kind of signal should i be seeing on IORQ?

 

if i start capturing data then turn on the system i seem to get some activity on IORQ but if the machine is already on and i start capturing data IORQ stays HIGH

Share this post


Link to post
Share on other sites

i have just started to look at this again with my new cheap usb logic analyser, i have noticed that the IORQ doesnt really do a great deal, MREQ and CLK seem to produce what i would expect to see. but what i am asking is what kind of signal should i be seeing on IORQ?

 

if i start capturing data then turn on the system i seem to get some activity on IORQ but if the machine is already on and i start capturing data IORQ stays HIGH

 

You should see a spike to zero in IORQ each time you press Reset, and if you see this spike, then should be also a spike to zero in 74LS138 output for SN76489 sound chip selection.

Share this post


Link to post
Share on other sites

OK so i am still working on this replacing chips and whatnot's trying to breath some life back into this thing. i have replaced the SN76489, both 74LS138's and the bios chip with a new, the thing still outputs a tone on the audio pin when powered up :(

 

i did notice something a bit questionable though on the solder side between u10 and u14 which are the ram chips that have been replaced with new +5v chips there is a solder pad connected to one of the chips, this is not present in my other colecovision which works, so i am thinking have i picked up a dead / broken board that actually never worked?

 

i removed as much solder as i could from this ram pin to see if it was bridged and after testing the traces do actually connect. can anyone help me out by letting me know if this is correct for a french rgb colecovision revision B board

 

post-18126-0-86930300-1432939927_thumb.jpg

Share this post


Link to post
Share on other sites

Hi sorry if this answer may be a bit late. I am in a similar position as you. I have a french CV which barely works. I have replaced all chips except the two 4066s, the Z80 and the bios chip. But none of this would fix anything.

BTW I confirm that the trace you mention in your last post is correct. This also results from schematics (the Dan Boris' ones, which are for NTSC CV, but the part around vram should be the same).

 

In the next few days I will try to replace the bios and CPU with ones from a working CV, see if that resurrects it. If that does not work then I am at a loss.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...