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8032 Rom's in spare slot? bad screen display

P

polishedball

Experienced Member
Joined
Mar 21, 2010
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114
Kinda of confused as I thought Slots UD11 and UD12 were spares in basic 4.0. I recently got a 8032 board working that used a rom in UD11 and is Basic4.0 (it was a fat 40 conversion i did years ago). I ask this because I am still trying to repair the original board that I put all new roms in and am wondering if something is a miss with the images I used. They came from this site (http://zimmers.net/cbmpics/clpets.html) the 6 pack Kernal,Edit,Char and Basic.

I am now just questioning myself as it is stuck on this screen (see images below of boards and screen) Any ideas from the look of the screen?

Thanks for any explanation anyone might have.

s.jpg


ss.jpg

sss.jpg


Thanks
 
OK this screen of garbage may be due to bad video RAMS. There is sort of an even and odd look to it which indicates the odd and even video RAM chips have different stuck bits. The space character which should be on the screen is sometimes seen as a # character. This indicates a hex 23 instead of a corect hex 20. Two LSB bits seem stuck on. There may be other issues. Be careful as they are solderd-in. I think there are four chips total. Do you know how to use solder wick to remove the chips safely?

Don't worry about UD11 and UD12. Those are spare slots meant for user machine language code. Someone must have put some utility software at address A000H. After you get the machine fixed you can try a SYS 40960 to see what it does.
-Dave
 
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The chips are all ready in sockets and replaced. You are referring to the SRAM's correct? I have a nice Hakko808 desolder tool that does a great job without no worries of lifting a trace. should i go after the 74LS373's next?
 
Also a bit off topic, but a cassette unit that works on the pet should work on a c64? I have one working on my PET but it won;t work on any of my c64's. I want to move some games using unicopy so I can try em out on the working pet I have.
 
dave_m said:
Don't worry about UD11 and UD12. Those are spare slots meant for user machine language code. Someone must have put some utility software at address A000H. After you get the machine fixed you can try a SYS 40960 to see what it does.
-Dave
Click to expand...

That is actually the working board, the sys returns (c) piacs any ideas what it is?>
 
I replaced the 373 and 244's that are in the ram section as well, the screen now looks like this. Is it still showing the same thing? Sorry for my ignorance on this. It almost seemed more correct prior to the replacement. Also on occasion I need to hit the power switch twice to get this screen and the boot beeps. Even when it doesn't boot it has the Phi2 clock on the cpu.

ssss.jpg
 
polishedball said:
The chips are all ready in sockets and replaced. You are referring to the SRAM's correct? I have a nice Hakko808 desolder tool that does a great job without no worries of lifting a trace.
Click to expand...
Yes the 2114 SRAMs at UC4,5,6 and 7. Are you saying you put in the sockets or there were sockets there already? The board I have did not come with sockets.
 
polishedball said:
Also a bit off topic, but a cassette unit that works on the pet should work on a c64? I have one working on my PET but it won;t work on any of my c64's. I want to move some games using unicopy so I can try em out on the working pet I have.
Click to expand...

The cassette unit should work. There may be a head alignment issue with the C64 tapes and your drive. Try to load a tape written by this drive into the C64 as an experiment.
 
polishedball said:
I replaced the 373 and 244's that are in the ram section as well, the screen now looks like this. Is it still showing the same thing? Sorry for my ignorance on this. It almost seemed more correct prior to the replacement. Also on occasion I need to hit the power switch twice to get this screen and the boot beeps. Even when it doesn't boot it has the Phi2 clock on the cpu.
Click to expand...

It does look a little worse. A beep would indicate it initalized the video RAM but this looks like the boot did not get that far. I take it you have no blinking square cursor? This is getting curiouser and curiouser. Hang in there. There are lots of guys here that have seen this kind of problem.
-Dave
 
Where are you getting these spare parts from? They seem to be making things worse! Have you checked your newly-fitted sockets for continuity, dry joints, etc.?

My gut reaction also says it's something around the video RAM, but it would be a good idea to diagnose the problem properly before replacing any more parts. What kind of test equipment do you have access to? A scope or even a logic probe would be handy for this one.

Having to power cycle twice to get it to boot may indicate a problem with the reset circuit, although ISTR similar problems can be caused simply by not waiting long enough between switching off and on again.
 
The screen when it boots now looks like the original shot I posted, it bounces between the two shots actually in a random order.

The parts came from http://www.unicornelectronics.com

I ohm'd out all the sockets I have replaced for shorts or opens.

I have a scope, probe, meter etc.

There is no blinking cursor.
 
Sure looks worse... at least initially it got to a prompt and was probably a fairly straightforward video problem; hard to know where to start now. Does it "bounce" while it's on or do you mean that when you reset it comes up one way or the other and stays that way?

Not usually a good idea to just replace parts at random, especially more than one at a time.

The cassette drives are compatible, but there aren't many C64 games that will run on a PET; what are you trying to move?
 
Solved the whole cassette thing, I had jiffydos turned on on the c64. Was able to move and play pet games on my working machine.

I was planning on just socketing some of the most common failed parts, then swapping them if needed. After the fact I realized I couldn't use the original parts as the pins were flush cut on the board and would go into the sockets.

I figure since I have side by side machines with one working, i'll go after some signals with the scope and see what might be different.

The screen does not change while active only after a power reset. It comes up most often to the first example still occasionaly the second.
 
Atleast they look cool if not fully working yet. The 4016 PET, I converted to an 80 and added the memory so they are basically exact. I'll pull the 64K memory expansion and normal it up before beginning to troubleshoot.

counter.jpg
 
My asking where the parts came from was more of a rhetorical question - I don't want to cause any grief with actual suppliers! ;-)

I'd have a look what's happening at the CRTC (UB13). Pin 16 might be a good place to start considering the mix of regular and inverse video characters. Otherwise possibly the video RAM address MUXes (UC8, 9 and 10).
 
They do look cool indeed and it's just a matter of time before they both show working screens; I take it that either they're on that counter very temporarily or you're single?

So both states are stable? Does the screen change when you type some characters in both states? Does it beep when you hold down a key for about 6 seconds and you hit the right margin? Does it still come up randomly if you wait at least 10 seconds before powering up?
 
MikeS said:
They do look cool indeed and it's just a matter of time before they both show working screens; I take it that either they're on that counter very temporarily or you're single?

Does the screen change when you type some characters in either or both states? Does it beep when you hold down a key for about 6 seconds and you hit the right margin?
Click to expand...

My work bench is full, so it was the counter for now. Yep I heard about it already, but heck I took the pinball machines out of the living room.

Nope no beep.
 
cosam said:
My asking where the parts came from was more of a rhetorical question - I don't want to cause any grief with actual suppliers! ;-)

I'd have a look what's happening at the CRTC (UB13). Pin 16 might be a good place to start considering the mix of regular and inverse video characters. Otherwise possibly the video RAM address MUXes (UC8, 9 and 10).
Click to expand...

Thanks for the tips on where to start.
 
polishedball said:
My work bench is full, so it was the counter for now. Yep I heard about it already, but heck I took the pinball machines out of the living room.

Nope no beep.
Click to expand...
Geez, where else does a pinball machine belong if not in the living room???

I added a few questions; also, does it beep when it starts up (in either state)?
 
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