C64 Screen & Border, no text.

[Abbub]

I'm at my wit's end on this system.

Commodore 64 Breadbox, early rev. motherboard.

It's powering up just fine. Getting the normal Dark Blue screen with a light blue border. No text.

So far I've tried swapping out the:
VIC
PLA
6510
Both CIA
Kernel, Basic, and Character ROMS
Took the SID out just for good measure.

Makes no real difference. Same (infuriating) dark blue screen with light blue border, not text. I have one cart (a game) that just results in a black screen on this system.

I've tried it on two power supplies, both of which work with other systems.

What's next to look at? The memory, I suppose?

 

[dabone]

I'd try the socket for the basic rom. What cart are you trying?

Quote from Ray's Site.

U3 901226-01 BASIC ROM
Blank screen w/ border. Cartridge works.

You have been to this page for help right? http://personalpages.tds.net/~rcarlsen/cbm/c64-ic.txt

If you can make one, a dead test cart is great to have.


Later,
dabone

 

[Abbub]

Yeah, among countless other sites, I've been to that one.

Are there handy instructions somewhere for making a dead-test cart? My google-fu has failed me.

 

[carlsson]

Some utility cartridges bypass the RAM check, e.g. later versions of Action Replay and possibly also The Final Cartridge. If you are able to hack or make your own cartridge, you could try to program an EPROM which will cause a quick boot, bypassing the RAM check. If that one would make text appear, perhaps even the Basic prompt and the computer crash whenever you tried to assign a variable, enter a program line etc, I suppose RAM strongly was to suspect.

 

[dabone]

I've used a music composer cart and a clowns cart, any commodore cart that uses the 326173-01 board is easy to mod into a deadtest cart.

I've posted a how to over on lemon for the jumper settings, and you either use a OLD style eprom, or mod the cart for a 27256/512 eprom (like I do.)

Later,
dabone

 

[Abbub]

Turns out it was a bad BASIC ROM compounded by a bad 24-pin socket. The initial BASIC ROM was bad. I pulled it, and while it was out, I put a 24-pin socket in. Unfortunately, the socket itself wasn't sound, so when I put a *good* BASIC ROM in the system, it STILL didn't work.

Sadly, I didn't find this out until after I had swapped out about half the chips on the board. Live and learn.

As for making a test cart. The only carts I have here are a Cinemaware Warp cart (fastload) and the game 'Dragon's Den'. I'm not going to sacrifice the fastload cart, but I did pop open the game. There are three 24-pin ROM locations on it. Two are populated. The first is U1, which is labeled Bremen and has a 317012-02 (5283) ROM in it. U2 is labeled OPC and has a 317013-02 (5283) ROM in it. U3 is labeled ROM/ROM/RAM and is unpopulated.