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View Full Version : 8032 Rom's in spare slot? bad screen display



polishedball
March 24th, 2010, 03:46 PM
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.

http://home.comcast.net/~polishedball/s.jpg

http://home.comcast.net/~polishedball/ss.jpg
http://home.comcast.net/~polishedball/sss.jpg

Thanks

dave_m
March 24th, 2010, 04:16 PM
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

polishedball
March 24th, 2010, 04:32 PM
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?

polishedball
March 24th, 2010, 04:35 PM
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.

polishedball
March 24th, 2010, 04:47 PM
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

That is actually the working board, the sys returns (c) piacs any ideas what it is?>

polishedball
March 24th, 2010, 05:29 PM
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.

http://home.comcast.net/~polishedball/ssss.jpg

dave_m
March 24th, 2010, 09:06 PM
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.
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.

dave_m
March 24th, 2010, 09:09 PM
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.

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.

dave_m
March 24th, 2010, 09:21 PM
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.

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

cosam
March 25th, 2010, 02:12 AM
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.

polishedball
March 25th, 2010, 04:09 AM
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.

MikeS
March 25th, 2010, 07:15 AM
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?

polishedball
March 25th, 2010, 07:39 AM
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.

polishedball
March 25th, 2010, 07:41 AM
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.

http://home.comcast.net/~polishedball/counter.jpg

cosam
March 25th, 2010, 08:08 AM
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).

MikeS
March 25th, 2010, 08:22 AM
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?

polishedball
March 25th, 2010, 08:25 AM
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?

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.

polishedball
March 25th, 2010, 08:25 AM
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).

Thanks for the tips on where to start.

MikeS
March 25th, 2010, 08:32 AM
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.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)?

mrmacca
March 25th, 2010, 10:06 AM
I think you should leave them right there. Thats Kitchen Chic that is :D

linuxlove
March 25th, 2010, 10:30 AM
I think you should leave them right there. Thats Kitchen Chic that is :D

But what if he's married? What would the wife say about the systems?
:P

polishedball
March 25th, 2010, 10:30 AM
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)?

Yes it does have the normal 4tone boot sound on power up.

mrmacca
March 25th, 2010, 10:39 AM
Yes it does have the normal 4tone boot sound on power up.

Good sign then :)

So.. Are you.. Married then..? If you are, respect is due :cool:

MikeS
March 25th, 2010, 12:17 PM
Yes it does have the normal 4tone boot sound on power up.It's really frustrating trying to remotely troubleshoot if you don't answer our questions...

Again:

- If you allow at least 10 seconds between power off and power on, does it still come up randomly in either of those two (and only those two) states?

- Once it's up, if you do nothing do both displays remain the same or do any locations change at all?

- If you type something or just hold down a typing key, do either of the displays change at all?
(I take it that even after holding the space key (for example) for ten seconds or so there is never a beep?)

and

- Which ICs did you replace?

polishedball
March 25th, 2010, 12:46 PM
It's really frustrating trying to remotely troubleshoot if you don't answer our questions...

Again:

- If you allow at least 10 seconds between power off and power on, does it still come up randomly in either of those two (and only those two) states?

- Once it's up, if you do nothing do both displays remain the same or do any locations change at all?

- If you type something or just hold down a typing key, do either of the displays change at all?
(I take it that even after holding the space key (for example) for ten seconds or so there is never a beep?)

and

- Which ICs did you replace?

With 10sec between power ups it 9/10 comes up onto the first screen. These screens never change and there is no active data in them, they remain the same. There is never a beep and nothing changes if typing or holding down a key till what would usually reach the end.

I replaced all the DRAMS, SRAMS, the 74LS244's in ram section and the 373's in the RAM section. This made no change in the screen. I also swapped the 6502 no difference, and the character rom no difference.

Thanks

MikeS
March 25th, 2010, 06:27 PM
With 10sec between power ups it 9/10 comes up onto the first screen. These screens never change and there is no active data in them, they remain the same. There is never a beep and nothing changes if typing or holding down a key till what would usually reach the end.

I replaced all the DRAMS, SRAMS, the 74LS244's in ram section and the 373's in the RAM section. This made no change in the screen. I also swapped the 6502 no difference, and the character rom no difference.

ThanksLooks like it's more than just a video problem then; if you still get the Commodore BASIC message that the first screen shows but the keyboard isn't recognized then I'd suspect one of the ROMS. Looks like it passes the RAM test but goes off into never-never land some time afterwards.

Sounds like you've got a programmer; if you've double-checked all the sockets and pins maybe it'd be worth while to read them and make sure they match the correct numbered images on Zimmers. You show both systems; I take it that this is the one with the EPROMS? 2532s except for a 2716 in UD7 (E0-8 )?

polishedball
March 25th, 2010, 06:54 PM
Sounds like you've got a programmer; if you've double-checked all the sockets and pins maybe it'd be worth while to read them and make sure they match the correct numbered images on Zimmers. You show both systems; I take it that this is the one with the EPROMS? 2532s except for a 2716 in UD7 (E0-8 )?

I'll read them back and compare checksums again. They were right when prg originally, but worth a check again. I used the images from zimmers making these. Thanks for the help, hopefully this weekend i'll have some time to really dig in and actually troubleshoot the board.

polishedball
March 25th, 2010, 07:59 PM
OK made some progress swapping out UC8, 9 and 10 as suggested, I also replaced the remaining caps that hadn;t been on the board. It now boots everytime and comes up to a cursor blinking and some can almost read text. When holding down space it moves the cursor and it beeps when hitting the end of the line. This is an updated picture. If anyone could give any more ideas on what to look at next. Thanks so much for the help so far. The garbage appears on the screen prior to the basic prompt comming up if that can help at all. Id did swap in some new SRAM again and it made no difference. The ram I am using is a replacement sub though part number AM9114CDC can anyone confirm that this can be used?

http://www.home.comcast.net/~polishedball/pg.jpg

polishedball
March 25th, 2010, 08:04 PM
I did swap the character rom and the edit rom with known goods this didn't make any improvement. Doing a checksum check on the remaining roms.

polishedball
March 25th, 2010, 08:15 PM
Verified programmed checksums to remaining roms all tested good.

MikeS
March 25th, 2010, 09:14 PM
OK; looks like we're sort of back where we were; I'd suspect UC6 and/or UC7.

Edit: I see that you did replace the video RAM; did you replace all 4 and nothing changed? 9114 should be an OK replacement.

If you did indeed replace all 4 and there was no change then I'd suspect UB6, UB7, UB8 and UC3 in that order.

What does it look like with UC6 and UC7 removed?

polishedball
March 25th, 2010, 09:37 PM
OK; looks like we're sort of back where we were; I'd suspect UC6 and/or UC7.

Swapped them with what I believe to be known good still have the same issue. If it is an sRAM issue would something change if I swapped UC4&5 with UC6&7. I'll also double check the socket work on them and ohm them out tomorrow. Gotta be to work in 5 hours. Any other ideas? Thanks again for your help and my apologies for the newbie mistake of not answering directly earlier your questions.

polishedball
March 25th, 2010, 09:50 PM
OK; looks like we're sort of back where we were; I'd suspect UC6 and/or UC7.

Edit: I see that you did replace the video RAM; did you replace all 4 and nothing changed? 9114 should be an OK replacement.

If you did indeed replace all 4 and there was no change then I'd suspect UB6, UB7, UB8 and UC3 in that order.

What does it look like with UC6 and UC7 removed?
UB6, UB7, UB8 are all socketed. I'll check them in my IC tester shortly. UC3 is not and as fate would have it I do not have a 74LS138 in my stock.
The screen looks like this with them removed.
http://www.home.comcast.net/~polishedball/eo.jpg

polishedball
March 25th, 2010, 09:58 PM
I'd suspect UB6, UB7, UB8 and UC3 in that order.


Ding Ding we have a winner, UB6 when tested in my checker came back as a 74LS185 not a 74LS244. Swapping this fixed it up. It now displays properly! Thanks so much for your guiding me through this.

John

mrmacca
March 25th, 2010, 10:22 PM
Another Pet Saved
:danceparty:

tezza
March 25th, 2010, 10:53 PM
Well done!

Another Pet rescue!

Tez

MikeS
March 25th, 2010, 11:10 PM
Ding Ding we have a winner, UB6 when tested in my checker came back as a 74LS185 not a 74LS244. Swapping this fixed it up. It now displays properly! Thanks so much for your guiding me through this.

JohnExcellent! Glad to see another PET resurrected.

Apologies if I sounded snarky about getting questions answered; I think we were just both editing our posts at the same time and missed the changes.

What part of the world are you in BTW?

polishedball
March 26th, 2010, 04:42 AM
What part of the world are you in BTW?

I live in Grand Rapids, Mi. Thanks again.