9" CRT vc 12" CRT

[giobbi]

Have you considered changing keyboards? ;-) I guess the 9" monitor would look funny on top of the 8032 base? ;-)

I only have 8032-sk models, one perfectly working and one working "more or less" (some issues) without keyboard.
So, swap the keyboards is not an option... :-(

But what is the difference between graphic keyb assy and business keyb assy? Is it just a ROM difference?

And what the pin 39 of the 6522 in the schematics
http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/pet/2001N/320349-3.gif
stands for? It's marked as "graphic"...

How about this: connect the keyboard from your 8032, plug in either set of ROMs with the appropriate (working) business KB ROM, put the corresponding graphic E ROM into the spare 'A' socket and calculate the checksum.

do you mean to use the working 8032 adding..? the original graphic E rom of the basic-2 OR the E rom image from basic-4 ?
I can easily do that, of course. I think I've already calculated the checksum of the original E rom when you asked me some days ago (see previous posts).

---edit: I'm using the rom image from zimmers, so is it interesting to calculate it by the 8032? Just a curiosity...

 

[MikeS]

The difference between the keyboards aside from the different labels and layout is just the way the keys are (inter-)connected, i.e. the layout of the matrix, and the 'E' ROMs just interpret a given key pressed (i.e. a connection between a column and a row) differently; there are subtle differences in the way SHIFT is handled, for example, but I can't think of anything that would prevent the PET booting.

No, I thought that the 3032-B, 8032 and the 8032-SK all used effectively the same keyboard with the same internal connector, so that you could 'borrow' it and temporarily have a useable 3032, and then use it to test the non-working E ROM in the actual 3032 itself (instead of the programmer or the 8032). I think when you tested it in the 8032 it matched; it can't hurt to check again vs. the Zimmers image, but I think it'll match as well.

As I said, I'm grasping at straws; double-check my summary of the situation, and maybe Steve or Dave (or someone else? anyone?) has an insight.

The Graphic line goes to sheet 8 where it just selects the alternate character set; nothing to do with the keyboard or ROMs.

Hmm... you may have hit on something: I think the two versions default to different sections; try replacing the character generator chip with one from the 8032. If nothing changes, carefully lift pin 19 out of the socket and alternately connect it to ground or Vcc and see if that makes a difference.

Do you have a cassette drive BTW?

 

[dave_m]

Hmm... you may have hit on something: I think the two versions default to different sections;

Mike,
I think I see your hypothesis. The only key difference between the editor ROMs is that the normal graphics ROM will set the "Graphics" bit to the character generator to select the alternate character set. So if there is some flaw in the character generator ROM in Graphics mode, only blanks are output? If this is true, the machine is really booting but there is no display on the screen. To prove it, a POKE 59408,12 might select business mode and get a screen display back?? POKE 59408,14 switches the other way.

Pretty thin, but doesn't hurt to try....

Or has Giovi ever tried burning a new character generator EPROM (2716 with no adapter)?

 

[dave_m]

But what is the difference between graphic keyb assy and business keyb assy? Is it just a ROM difference?

I don't think there are any electronics inside the keyboards. Just different switch matrixes.

 

[giobbi]

People,

this computer is scaring me...

Now it works with Basic 4.0 and graphic keyboard, but not with Basic 2.0 and graphic keyboard! - I tried both original B-2 Rom and B-2 image on 2732 eprom at $0800

What I did that worked?

Well, I replaced the MB8116E ram chips, that should be equivalent with 4116. Maybe this made the difference? I think no, because it is quite strange; the Basic 2 set isn't working yet, even with the original 4116 chips.

For the B4-edit-graphic-keyboard ROM I'm using a 2732 eprom programmed starting at $0800 instead of the 2716 eprom (ehm, I put the 2716 in the wrong way and it burned; yes, fire inside its window, I didn't know you can fry an eprom if you put it turned by 180°... I already ordered some on eBay but they will take a long time to arrive)

Ok, the computer is working now but I still wish to know what's going on: if you don't know why and how the problem has gone, it will come back soon. Murphy docet

Actually I have to clean the keyboard, many keys refuse to work or almost refuse and you need to tap them with an hammer in order to see the char to appear on the monitor ;-)

Of course I have a cassette unit; I remember I read the pet is compatible with VIC-20 tape recorder; if this is true, I should have almost 20 units :D ; if not, I have its original black tape but I don't know if it's working.

Still to solve: it is displaying 15359 bytes free. Is there any diagnostic program I can use in order to detect the faulty ram, or something to check?

 

[dave_m]

Actually I have to clean the keyboard, many keys refuse to work or almost refuse and you need to tap them with an hammer in order to see the char to appear on the monitor ;-)

Congratulations on the job so far! There are ways published to clean the keyboard very well, but a quick and dirty way is to remove keyboard from the PET and turn upside down and remove the screws on the circuit board and carefully remove board (you may have to unsolder two wires - remember where they go). Be careful as all the parts are loose, don't let them go flying around the room. Rub lead from a pencil on the black foam tips, this will make them more conductive. This may work only for a while before you have to clean them properly or use a rubber keyboard repair kit from MG Chemicals (part number 8339)

 

[MikeS]

Hate to disagree with Dave, but none of the keyboards I've 'rejuvenated' had "loose" parts (as long as you didn't remove the keytops).

Remove the keyboard, undo the 20 or so screws and the shift lock wires; clean the pcb with an eraser and the pcb and the conductive tips of the keys with alcohol. Put a few screws back in and test; with luck that'll be all you need to do.

 

[giobbi]

Congratulations on the job so far! There are ways published to clean the keyboard very well, but a quick and dirty way is to remove keyboard from the PET and turn upside down and remove the screws on the circuit board and carefully remove board (you may have to unsolder two wires - remember where they go). Be careful as all the parts are loose, don't let them go flying around the room. Rub lead from a pencil on the black foam tips, this will make them more conductive. This may work only for a while before you have to clean them properly or use a rubber keyboard repair kit from MG Chemicals (part number 8339)

Great, I didn't know about the rubber or the chemical product; one thing I discovered is that often people left those old computers in a garage with some other stuffs on the keyboards, so after some time (some years!) the black foam tips get deformed and take the shape of the pcb traces. So a way to solve this problem is to rotate by 90° the membrane of every key; this way the deformed foam tip no longer match with the pcb trace shape. It works quite often.

But, please don't leave me now! I still have the RAM problem to solve, just 15359 bytes free. These last days it was giving me the full amount of ram or just this value, randomly. Now I'm getting only this value.

Have you any idea about how to check ram chips? Some poke/peek to read every ram location? Some basic program I can type?

 

[MikeS]

...But, please don't leave me now! I still have the RAM problem to solve, just 15359 bytes free. These last days it was giving me the full amount of ram or just this value, randomly. Now I'm getting only this value.

Have you any idea about how to check ram chips? Some poke/peek to read every ram location? Some basic program I can type?

It is quite probably the same bit (chip) in the entire upper 16k; the simplest test is:
POKE 16384,0RINT PEEK(16384)OKE 16384,255RINT PEEK(16384)
If you don't read what you wrote, the wrong bit will tell you which chip.

If they're socketed and you have a spare of course you can just replace one at a time; if not, "piggy-backing" sometimes reveals the bad one.

Congratulations!

Looks like we're almost there; of course we still don't know what's wrong with the BASIC2 set... definitely a curious problem.

Regarding the 8032-SK keyboard, this may interest you; it's presently being redesigned, but if you don't mind using a PC keyboard this may get you going. Jim Brain is a member here so I'm sure he can give you more info, here or on his site.

http://store.go4retro.com/c-key-keyboard-adapter/

 

[dave_m]

Hate to disagree with Dave, but none of the keyboards I've 'rejuvenated' had "loose" parts (as long as you didn't remove the keytops).

Mike, Oh, lucky you. You never dropped a spring. Haven't you picked up a keytop? Don't you have ANY curiosity! :D

clean the pcb with an eraser...

A pink eraser! You are supposed to use an expensive contact cleaner. You cheap Canuck.

Actually I don't really know how Giovi fixed his PET, but sometimes you just have to thank the computer gods.
-Dave

 

[giobbi]

hey hey hey, please put away those champagne bottles, please, the party for the "12-year-fix" hasn't begun yet .... because the fix is still on the run

I have another trivial problem... It sometimes hangs. Sometimes simply the cursor disappears, sometimes on the screen appear some lines and chars. But it hangs.
It believe it is due to some bad contact (probably a ROM that tends to pull out from the socket, maybe I could make a little solder on two pins to fix it to the socket?); I'm searching for it, but if you have some better idea, please tell me!

8116 RAM chips weren't the problem, I tried to put some in place of 4116 chips, and they're working.

For sure I changed an IC 74xx with a 74LSxx (the original schematics is telling 74LSxx) but I forgot what! (what the hell, I always keep track about what I'm doing :-x)

Cassette tape is working, I was able to load a program from a 30 years old tape and to get a ?SYNTAX ERROR IN 400 too! One of the most longevous bugs in the history

I need to do a better clean inside the keyboard, the fast clean of yesterday night worked just partially...

And of course still I don't know (and maybe I will never know)why:

- the BASIC 2 doesn't work with the graphic keyboard ROM;
- the BASIC 4 with the graphic keyboard ROM started to work apparently alone.

I also with to write a page on my site telling this millennium-fix, what I did and what I discovered. If I will post a draft here, would you be so kind to correct it (both poor english and poor technical knowledge) ?

 

[MikeS]

Mike, Oh, lucky you. You never dropped a spring. Haven't you picked up a keytop? Don't you have ANY curiosity! :D

Oh, I've dropped more than my share of springs and tiny screws, and turned opened keyboards upside down only to have a cascade of springs, toggles etc. raining on my feet (beware of IBM M2's!), but Commie keyboards have never been a problem. Mind you, they did use various suppliers and maybe I've just been lucky with mine, but the keys, stems and springs all stay in place on the upper half (unless you actually pull off the individual keytops) and a cleaning is all any of them have needed (so far).

A pink eraser! You are supposed to use an expensive contact cleaner. You cheap Canuck.

Tsk; frugal, and eco-conscious! It's actually white...

Actually I don't really know how Giovi fixed his PET, but sometimes you just have to thank the computer gods.
-Dave

Like I told him in my first reply, most of the time we just supply encouragement and the occasional piece of advice; usually it's the OP who actually fixes the problem in the end.

 

[MikeS]

hey hey hey, please put away those champagne bottles, please, the party for the "12-year-fix" hasn't begun yet .... because the fix is still on the run

Oh well, I think it deserves at least a bottle of cheap wine.

I have another trivial problem... It sometimes hangs. Sometimes simply the cursor disappears, sometimes on the screen appear some lines and chars. But it hangs.
It believe it is due to some bad contact (probably a ROM that tends to pull out from the socket, maybe I could make a little solder on two pins to fix it to the socket?); I'm searching for it, but if you have some better idea, please tell me!

I think we need to encourage Dave to expand on the PETtest diagnostic capabilities...

And of course still I don't know (and maybe I will never know)why:
- the BASIC 2 doesn't work with the graphic keyboard ROM;
- the BASIC 4 with the graphic keyboard ROM started to work apparently alone.

Might well be related to your continuing RAM and intermittent hang problem.

I also with to write a page on my site telling this millennium-fix, what I did and what I discovered. If I will post a draft here, would you be so kind to correct it (both poor english and poor technical knowledge) ?

Might be better to send it in private messages...

 

[dave_m]

I have another trivial problem... It sometimes hangs. Sometimes simply the cursor disappears, sometimes on the screen appear some lines and chars. But it hangs.
It believe it is due to some bad contact

Maybe not so trivial; intermittent connections can be hard to find as you have found out. When the cursor quits, it usually means that somehow the 60Hz interrupt handler routine is not running. How long before this starts happening? Is something getting hot? If it is a component, there is a 'cold spray' can you can use to troubleshoot, but I'm guessing it is a connection. Mike & I will hang in there with you. You have shown amazing 'staying power'. Most would have thrown the PET into the trash by now.

For sure I changed an IC 74xx with a 74LSxx (the original schematics is telling 74LSxx) but I forgot what! (what the hell, I always keep track about what I'm doing :-x)

Oh, no, you did find something, but can't tell us!!!

 

[giobbi]

Ok, I cleaned better the keyboard, now it's running like a Ferrari on a flat, black asphalt -- a common cleaning product I stole in the kitchen did the job.

I think the last problem I have was due by a ROM that's trying to pop out from its own socket. It happened while the computer was cold but later it didn't appear again, so it shouldn't be a "defective-when-hot" component problem. I pushed the ROM in the socket again, but if it will try to escape from its socket I will sold it on a fresh socket and put the socket inside its socket (yep, "she sells sea-shells..." )

Dave, I have to admit I discovered something: I discovered that once in a lifetime I had enough willpower to fight until to win, while normally if I can't solve this kind of problem in ten minutes, I quit. But you're wrong, the trash isn't the right way: gasoline and matches *IS* the right way!!! :D

I think it's all folks, let's open that champagne... but I strongly believe that some credits are deserved!

THANK YOU SO MUCH!!! -- This one's for you:



--- Giovi

p.s. don't go away, it will hang a minute after I will click on "post reply" ;-)

 

[dave_m]

I think we need to encourage Dave to expand on the PETtest diagnostic capabilities...

Mike, OK, but at the moment I'm helping my nephew (well, OK, grand-nephew) with a class in Probability and Statistics. It's a summer session so it should not take too long. Don't ask me to multi-task as those days are over. I can barely walk and chew gum.

How should the results of the checksums be output? Should I assume the display is working or do I send morse code on the user port??

First off I need to fix the bugs I introduced in the 8032 version of Eudi's 3032 program. Now that you sent me the Commodore Assembler, I can develop the code all on the PET. Of course I'll need PETDisk to get it off the PET and into a PC for uploading. You have to test it for me because my kernel F000 ROM is not on a socket.
-Dave

 

[giobbi]

Hi Mike and Dave,

IN TROUBLE, AGAIN :-(

of course, nothing is easy in this life...

I worked on it yesterday night for many hours, loading programs from old tapes and saving them in fresh tapes, just to be sure. No problem at all when I switched it off at 2:00 AM, more or less...

Today I tried to switched it on and, surprise!, black screen again!

I put the petester ROM in the kernal socket, and I'm getting a screen full of "b" instead of "g". It seems that it works fine only when it's hot.

I checked all the RAM chips replacing all, once at time. I also checked the 74153 and 74244 chips involved in the RAM schematics, no changes. This time it doesn't work either with business keyb ROM and graphic keyb ROM.

Honestly I was expecting the problem will appear, since I didn't really find where it is.

Exactly what does "b" page stands for? And what should I check now.

btw I'm leaving it on just to see if it will come back to life when warm...

-- Giovi

 

[MikeS]

Grrr... :curse: :wallbang: :machinegun:

Saw your PM; no time now, will think about it; maybe Dave has an inspiration in the meantime.

At least PETtest is still running.

 

[giobbi]

Grrr... :curse: :wallbang: :machinegun:

hoping emoticons weren't for the fact I bothered you in PM ;-)

Do you know what the page full of "b" stands for? Bad ram, if I'm right, but exactly what kind of test is done? In other words, what should I check in first?

 

[dave_m]

Giovi,
We will re-group and will find the problem. At the very worst, we can use a small module called PETVet from a person on this forum (gubbish) to bypass all the ROM and RAM on your board first to get the PET running, but also to be able to troubleshoot your on-board memory more easily. See bitfixer.com for some details.

In the mean time perhaps you can hook a switch to the /RESET signal (to ground) to perform a reset when the machine is warm so you won't have to cycle power so much as it is stressful on the power supply, CRT, etc. You can get to the RESET easily at the expansion connector on the side of the machine J4-22. Keep up your spirits!