PDA

View Full Version : Pet 8032 board repair question.



prime
December 18th, 2016, 05:46 AM
Hi all,

I have a bare 8032 board ASSY no 8032080 (note no suffix), which I would like to try and get going, it was at one time partially functional, so I suspect a ram or buffer fault somewhere.

However the original owner wanted to keep the PET case & monitor which he has since re-purposed.

I do have a complete 3008 (upgraded to 32K) machine that I can use as a testbed.

I realize that the two boards are different as the 8032 has a 6845 CRT controller whereas the 3008 just has TTL logic for it's video.

But are the voltage inputs, keyboard and monitor compatible between the two machines ? I do notice from the 8032080 schematic that it can be jumpered for 40 column opeartion which I would imagine that I would have to do for the 3008's monitor?
But would I be OK using my 8003 case / PSU / Keyboard to test the 8032 board?

If not I guess I'll just have to figure out a way of powering the board and getting video out......

Cheers.

Phill.

KC9UDX
December 18th, 2016, 05:58 AM
I may be wrong, so maybe wait for one of the guys with more experience with Universal boards, but I don't think you have to change anything, not even the 40 column jumper. I think 80 will work just fine except be harder to read.

MikeS
December 18th, 2016, 08:06 AM
Maybe someone else can confirm, but AFAIK:

1 - Power supply is identical, no problem.
2 - Keyboard layout is probably different.
3 - Monitor is not compatible as is (wrong scan rate).

Items 2 and 3, as well as 40 vs. 80 columns, could probably be resolved by burning and installing a new E000 edit ROM; maybe Steve G will jump in with suggestions?

m

dave_m
December 18th, 2016, 08:59 AM
I think the EDIT ROM needed is 901498-01 for Normal (graphics) keyboard, with CRTC, 40 col, 50 Hz.
Check to see if you currently have the 901474-04 ROM for Business keyboard, CRTC, 80 col, 50 Hz.

All binary images to burn a 2716 EPROM are HERE (http://zimmers.net/anonftp/pub/cbm/firmware/computers/pet/index.html).

Steve Gray will know if it would be safe to run as-is, and if the jumpers in main board for 40 column are needed. I think the jumpers are only for a fat 40 characters with the 12" monitor.

As Mike indicated, The scan rate for the 12" monitors is 20 KHz, while the rate for the 9" monitor is around 15.5 KHz. I don't know if it would bother the 3008 video board and screen to run with 8032 EDIT ROM. Where is Steve? <smile>

MikeS
December 18th, 2016, 09:56 AM
Steve Gray will know if it would be safe to run as-is, and if the jumpers in main board for 40 column are needed. I think the jumpers are only for a fat 40 characters with the 12" monitor.
I would think that it would work fine in 80 column mode, at least well enough for testing; to convert to 40 column mode you have to move the 10 obvious jumpers plus three other sets, cut one trace and replace the edit ROM.


As Mike indicated, The scan rate for the 12" monitors is 20 KHz, while the rate for the 9" monitor is around 15.5 KHz. I don't know if it would bother the 3008 video board and screen to run with 8032 EDIT ROM. Where is Steve? <smile>This is the main reason why you need to replace the edit ROM even if you keep 80 column mode; it determines not only the keyboard layout and 40 or 80 column mode, but also the video timing.

I believe Steve will have a suitable ROM with 9" monitor (NTSC) timing ready to go, or even a set of instructions to roll your own; he did a lot of research in the course of developing his colour PET.

m

prime
December 18th, 2016, 01:49 PM
Right, I've replaced the 6502 and the 6520 (though I have used the compatible 6821, as I have a load of those and no 6520s....I do have a couple of the WD 6521s though).

I've put sockets in and replaced two of the 2114s that where missing along with UB6, UB7 (LS244) and UB8 (LS373).

When I power on after a second or so I get what sounds like a two tone bleep from the speaker, which is the same every time I power on.
I also get a patten of squiggles in the middle of the monitor but this is stable and no high pitched whines from the monitor, but still don't want to leave it powered on too long just in case :(
Hitting keys on the keyboard doesn't seem to do anything on the screen, the keyboard is one of the original ones with the symbols on the top row and the numbers on the keypad.

So it's partly alive :)

Cheers.

Phill.

dave_m
December 18th, 2016, 03:31 PM
When I power on after a second or so I get what sounds like a two tone bleep from the speaker, which is the same every time I power on.
I also get a patten of squiggles in the middle of the monitor but this is stable and no high pitched whines from the monitor, but still don't want to leave it powered on too long just in case :(
Hitting keys on the keyboard doesn't seem to do anything on the screen, the keyboard is one of the original ones with the symbols on the top row and the numbers on the keypad.



Can you post a screen photo? The beeps are good. It means the start up was normal. Apparently the screen is not being cleared for some reason. So you decided to run with the normal 8032 EDIT ROM? Gutsy is as gutsy does.

MikeS
December 18th, 2016, 07:24 PM
...
I've put sockets in and replaced two of the 2114s that where missing along with UB6, UB7 (LS244) and UB8 (LS373).
So we're not actually talking about an 8032 but a FAT40 4032 that you're upgrading to an 8032?

I think I would have tried to get it going as the 4032 before adding extra variables and complications; if you're still using the 4032 ROM then you'll surely have issues and it'll be confusing trying to separate symptoms into ROM incompatibility, monitor incompatibility, configuration errors etc.

prime
December 18th, 2016, 10:11 PM
So we're not actually talking about an 8032 but a FAT40 4032 that you're upgrading to an 8032?

I think I would have tried to get it going as the 4032 before adding extra variables and complications; if you're still using the 4032 ROM then you'll surely have issues and it'll be confusing trying to separate symptoms into ROM incompatibility, monitor incompatibility, configuration errors etc.

No the board is as far as I know an 8032, the previous owner had removed those chips trying to trace the original problem, I merely replaced them.

Sorry if I didn't make this clear :)

Cheers.

Phill.

prime
December 19th, 2016, 12:07 AM
Can you post a screen photo? The beeps are good. It means the start up was normal. Apparently the screen is not being cleared for some reason. So you decided to run with the normal 8032 EDIT ROM? Gutsy is as gutsy does.
I decided to try it without swapping the ROMS initially, as the consensus of opinion seemed to be that the monitor wouldn't go bang! :) What I'm looking like I'm getting is an unsynced raster in the middle portion of the screen which makes sense based on what people have said about the scanrates.

I'll try burning a new EDIT ROM this eveining, if I can find the PSU for my programmer :) :)

Cheers.

Phill.

sjgray
December 23rd, 2016, 05:26 PM
I think the EDIT ROM needed is 901498-01 for Normal (graphics) keyboard, with CRTC, 40 col, 50 Hz.
Check to see if you currently have the 901474-04 ROM for Business keyboard, CRTC, 80 col, 50 Hz.

All binary images to burn a 2716 EPROM are HERE (http://zimmers.net/anonftp/pub/cbm/firmware/computers/pet/index.html).

Steve Gray will know if it would be safe to run as-is, and if the jumpers in main board for 40 column are needed. I think the jumpers are only for a fat 40 characters with the 12" monitor.

As Mike indicated, The scan rate for the 12" monitors is 20 KHz, while the rate for the 9" monitor is around 15.5 KHz. I don't know if it would bother the 3008 video board and screen to run with 8032 EDIT ROM. Where is Steve? <smile>

Steve is christmas shopping, visiting relatives and dealing with colds and fevers... why is everyone here? ;-)

Anyway, it would be more accurate to say the computers put out a 15 or 20 kHz signal. Monitors, at least old ones, generally can handle a small range rather than a set kHz. Those monitors all have internal controls for vertical and horizontal adjustment. Commodore chose to only expose the brightness to normal users. Afaik both 9" and 12" can handle either 40 or 80 columns and should be adjustable to handle either 15 or 20 kHz. Of course, take care when fiddling around with those contols!.. very high voltages are lurking.

I did build some 80 column edit roms for both ntsc or pal video and either normal or business keyboard. One of them should work. The universal dynamic motherboard does need to be properly jumpered for 40 or 80 columns regardless of which monitor is used.

Gotta go take some tylenol. Ttyl.

Steve

Edit: to clarify.. proper jumpering for proper operation. Infact you can use a 40 or 80 column edit rom regardless of the jumpers since the crtc timings are identical.. its the jumpers that determine how fast the pixels are clocked out at and how video ram is accessed. One thing you can NOT do is install ram for 80 columns but have the jumpers set to 40.

prime
December 24th, 2016, 06:47 AM
I did build some 80 column edit roms for both ntsc or pal video and either normal or business keyboard. One of them should work. The universal dynamic motherboard does need to be properly jumpered for 40 or 80 columns regardless of which monitor is used.

Edit: to clarify.. proper jumpering for proper operation. Infact you can use a 40 or 80 column edit rom regardless of the jumpers since the crtc timings are identical.. its the jumpers that determine how fast the pixels are clocked out at and how video ram is accessed. One thing you can NOT do is install ram for 80 columns but have the jumpers set to 40.

Which is odd as this board is jumpered for 40 col, but as far as I can tell, has always had 4x2114 video RAMS on it plus buffers, just sent the original owner a message to find out if they where there when he obtained it, as there where two missing buffers and a latch and two of the 2114s, but it looked like they had been desoldered rather than never fitted.

Which ones need to be removed for 40 col operation?

Cheers.

Phill.

prime
December 24th, 2016, 06:52 AM
Right some progress,

Turns out the main RAM was bad, as I was only getting one bleep from the speaker, by burning a custom edit rom, with a loop in it accessing the video chip I determined that the thing crashed every time it did an RTS, so suspected bad RAM and replaced, now starting with mutiple bleeps and initializing video chip.

Now the display is starting so getting some display, most of the time it just displays a single @ at the top right, occasionally multiple lines of @ Steve suggested that for 40 col operation I might need to disconnect half of the Video RAM, so will try that later as it's now socketed.

Cheers.

Phill.

dave_m
December 24th, 2016, 09:38 AM
Now the display is starting so getting some display, most of the time it just displays a single @ at the top right, occasionally multiple lines of @ Steve suggested that for 40 col operation I might need to disconnect half of the Video RAM, so will try that later as it's now socketed.



As Steve stated if the jumpers are set for 80 columns then leave all four video RAMs installed. Getting some '@' instead of a space character may mean some of your video RAMs are bad. Replace UC5 and UC7 2116 RAM chips.

sjgray
December 24th, 2016, 10:50 AM
You can leave all rams installed in 40 column mode provided you remove the odd video latch (UB eight) completely, or disconnect pin 1 (Commodore should have added a jumper there).

Steve

prime
December 25th, 2016, 12:32 PM
Annd it's working and now upgraded to 32K, seems to have had a bad ROM (901465-23) after blowing a copy into a 2532 it sprang to life.

Next task, test and replace where working all the chips I desoldered (and replaced with known good ones) whilst debugging the problem.

Also try and cook up an editor rom with support for the 9" monitor and Graphics keyboard, I'm going to put the 3008 board back in the case when I'm done as that is the correct one for this machine, but would be good if I could just swap between the two wne I want as I only have one complete machine, the 8016 I only have the board for.

I did try with Steve's ROM sources, compiling for NTSC, 40 columns, but the HS still seems to be happening at 20KHz rather than 16, so I get a display but it's not correct, was good enough to test with but would be good to get it right :)

Incase it's important the 3008 is a UK machine.

Cheers.

Phill.

sjgray
December 26th, 2016, 08:59 AM
That seems strange. I know the NTSC timing files are correct, because I am using them for ColourPET. Perhaps your edit.asm settings are off? Did you try one of the pre-assembled roms in the "\binaries" directory?

Steve