Videopac G7000 CPU needed

[xrbrevin]

Im new to these machines, im mainly an Atari 8bit-er but ive dabbled with other makes to a lesser extent. As a kid I was always intrigued by the Philips Videopac G7000 so I just took ownership of one that boots to a black screen with audio. It is the later revision PCB with internal PSU and hardwired joysticks.

I did a composite mod but the outcome is the same altho it does confirm a signal is being generated. 5v supply is good too. There doesnt appear to be a TEA1002 IC so im now inclined to swap out the CPU - until i found that they are a mask-ROM type and a generic one will not do. So I considered a 8748 instead as I have a TL866 programmer but it is not a supported device..!

Does anyone know where i can source another CPU or is a 'workaround' adapter available for the TL866 programmer to support the 8748?

Cheers!

 

[xrbrevin]

 

i have found this:

https://www.mattmillman.com/projects/hveprom-project/an-easy-to-build-mcs-48-8748-8749-8741-8742-8048-8049-programmer-reader/

might be worth a try if i can obtain the OS ROM file

[xrbrevin]

ok, ill continue this topic for what its worth. it may help people in future.

 

i built the EPROM programmer and it works fine. i read the EPROM part of my CPU ok, saved the .bin file and burned it to the 8748 ok too 🙃 (might mean my CPU is ok?)

i tried the 8748 in my G7000 but still just gives a black screen - gah!

 

i metered up the pins on the socketed ICs for continuity and noticed nearly all have dry solder joints. motivated with iron in hand, i reflowed all 3x sockets with fresh solder. in doing so i had managed to uproot the black ground wire at the motherboard end from the PSU. i proceeded to strip the insulation but the knife had a little beaded chain dangling down - it made contact with some part of the PSU (a cap?). i got a "fzzt" and now i dont have power..! this chain has now been removed... im hoping it is a fuse or something obvious.

 

so it continues. here is the OS ROM in case anyone needs it. it came from my G7000 - the type with hardwired joysicks, hardwired internal power transformer, hardwired RF.

 

G7000_os.bin

[jimj]

Only two posts (with a couple attachments), but someone faced a similar challenge here:

http://videopac.nl/forum/index.php?topic=3372

I noticed the g7400.bin file posted there is different than your bin file.

[xrbrevin]

On 12/19/2023 at 3:14 PM, jimj said:

Only two posts (with a couple attachments), but someone faced a similar challenge here:

http://videopac.nl/forum/index.php?topic=3372

I noticed the g7400.bin file posted there is different than your bin file.

thanks, but i cant see the attachments. do i have to be a member?

i have built my RGB mod board, just the cables left to do

[xrbrevin]

merry xmas !! 🎅

i built the cable but still got no display on my RGB SCART TV

but i remembered an additional low voltage signal needs to be included in the SCART connections to enable the RGB input. hmmm...

i then reached for my RGBtoHDMI device and pondered... i already have a 5pin DIN cable for this for my Oric so i deduced a compatible pinout, found a spare socket, powered up the iron, and set to. audio would have to catered for seperately but this is still the research stage..

 

it lives! its my oldest system and it has the newest display tech - the irony! 🙃

so, it was the display circuit all along. maybe the pal encoder or an issue in the modulator but for this survivor, it's getting a case mounted RGB DIN port with a 3.5mm audio next to it.

it'll be nice to have it permanently reassembled but i got xmas commitments impending!

 

i'll post again when it is in some semblance of order, need to address that " ELECT G ME" signal too

Edited December 25, 2023 by xrbrevin

[jimj]

You do need to be signed in videopac.nl (but accounts are free).

 

That's some impressive hardware hacking.    It's strange how some of the video output is missing though.  In addition to SELECT GAME, there should be text in the Speedway and Spin Out games.

[xrbrevin]

Hi,

thanks, its still a little janky!

i read somewhere that the blanking signal for SCART RGB enabling is taken from pin9 of the PAL encoder. so i decided i should fit a more suitable monitor port that has sufficient pins for this and audio too. then i can re-try using the SCART connection instead of the RGBtoHDMI device.

the green signal is the one thats amiss. when the parts arrive for the above, i will desolder the PAL encoder and fit a socket. if there is still no joy then i will get the oscilloscope out!