Dick Smith Super 80 computer kit

[Peter]

Whether you choose the Dick Smith or El Grafix set is up to you,

as is the way you implement it. On my non-working Super-80, I

have both eproms wired up, with a switch to choose which one

I want to use.

 

I'd rather the EL-Graphics upgrade, just need to see a schematic for that and since I've replaced the sockets with machined pin versions the durability is much greater. I'll create a DIP header to plug into the 2513's socket as I have the hardware to do that it shouldn't be a problem.

 

I haven't had any success with the memory curruption mod. I've made the changes but the problem still exists. I've tripple checked and can't see anything wrong with the changes. I'm also getting a problem with the characters, the rightmost pixel of each char is missing. Sometimes they appear but then dissapper so the 2513 is OK, there's a signal emminating from all the 2513 output pins. It could be a socket issue again.

[Garos]

 

Whether you choose the Dick Smith or El Grafix set is up to you,

as is the way you implement it. On my non-working Super-80, I

have both eproms wired up, with a switch to choose which one

I want to use.

 

I'd rather the EL-Graphics upgrade, just need to see a schematic for that and since I've replaced the sockets with machined pin versions the durability is much greater. I'll create a DIP header to plug into the 2513's socket as I have the hardware to do that it shouldn't be a problem.

 

I haven't had any success with the memory curruption mod. I've made the changes but the problem still exists. I've tripple checked and can't see anything wrong with the changes. I'm also getting a problem with the characters, the rightmost pixel of each char is missing. Sometimes they appear but then dissapper so the 2513 is OK, there's a signal emminating from all the 2513 output pins. It could be a socket issue again.

 

Hi guys and welcome z80,

lots of excitement on the S80 front I see! I dont' recall having any problem with the sockets, perhaps I was lucky. I am still very tempted to attempt to have an s80 pcb etched (extrapolating from images of the s80's available), unfortunately finances are a real issue. I may have mentioned that I am to be made redundant in 5 weeks, and attaining a suitable job won't be easy. Perhaps there is a market in copies of vintage computer kits (currently I don't even have any test equipment).

 

z80 you mentioned the temptation to produce an s80 emulation using sram... please keep us posted if you decide to follow that road. I don't know that you are aware of the Yahoo group Peter has started; dick_smith_super-80 (please join, our numbers are few, well 2) Peter, it may be worth posting the highlights of this thread on the group. It was very excited to see the beginnings of the manual there (thanx).

 

Anyhow, glad to see your efforts beginning to fruit.

[Robert]

I'd rather the EL-Graphics upgrade, just need to see a schematic for that and since I've replaced the sockets with machined pin versions the durability is much greater. I'll create a DIP header to plug into the 2513's socket as I have the hardware to do that it shouldn't be a problem.

 

I haven't had any success with the memory curruption mod. I've made the changes but the problem still exists. I've tripple checked and can't see anything wrong with the changes. I'm also getting a problem with the characters, the rightmost pixel of each char is missing. Sometimes they appear but then dissapper so the 2513 is OK, there's a signal emminating from all the 2513 output pins. It could be a socket issue again.

 

The El-grafix kit consisted of 1x 2732 eprom, and 1x 74LS165 chip. The circuit diagram was in one of the books I brought over on my visit, the page is titled "Constructing the El Graphix Kit 4 Graphics Kit".

 

The missing dot can only be caused by a bad socket on U23 or the 2513. U23 combines the outputs of the 2513 into a stream of dots, which appears on your monitor screen.

 

If you're really sure you've done the memory mod properly, look for bad sockets on the RAM or the chips that address it. Have you tried using 32k or 48k of RAM to see if it changes anything?

[Peter]

The El-grafix kit consisted of 1x 2732 eprom, and 1x 74LS165 chip. The circuit diagram was in one of the books I brought over on my visit, the page is titled "Constructing the El Graphix Kit 4 Graphics Kit".

I'm sure I saw it but mistook it for the Dick Smith one.

The missing dot can only be caused by a bad socket on U23 or the 2513. U23 combines the outputs of the 2513 into a stream of dots, which appears on your monitor screen.

I've resocketed both and still have a missing dot. I'm not too worried about it yet but I'll put the CRO on it soon to see what's happening with the signals.

If you're really sure you've done the memory mod properly, look for bad sockets on the RAM or the chips that address it. Have you tried using 32k or 48k of RAM to see if it changes anything?

I'm seeing random characters appear all over the place. A large portion turn into @s

 

I don't think I'd have any video display if the mod was done incorrectly. I've even resocket U76 and U50, no improvement. I've probably missed something. Those solder fumes can't be good for me! I've got brand new 4116s in there but you may be right the sockets could be the problem.I'll put another row in and see what that does.

[Robert]

No probs, let me know what you find.

[shred]

I'm seeing random characters appear all over the place. A large portion turn into @s

 

If you are seeing spaces (ASCII value of 32) turn into @ (ASCII value of 64), then try changing the DRAM chip that holds bit 5 of the video memory (I think it's U68 if you only have 16k fitted). If you don't have a spare 4116 floating around, just swap the "bit 5" RAM chip with the "bit 0" chip and see if the space characters start changing into ! characters (ASCII 33).

 

When I first assembled my Super 80, tricky dickies supplied me with a faulty RAM chip, so I found that one out the hard way.

[Robert]

Another Super-80 user? Welcome Shred!

[Peter]

If you are seeing spaces (ASCII value of 32) turn into @ (ASCII value of 64), then try changing the DRAM chip that holds bit 5 of the video memory (I think it's U68 if you only have 16k fitted). If you don't have a spare 4116 floating around, just swap the "bit 5" RAM chip with the "bit 0" chip and see if the space characters start changing into ! characters (ASCII 33).

 

When I first assembled my Super 80, tricky dickies supplied me with a faulty RAM chip, so I found that one out the hard way.

 

Hi Shred,

 

I will try that, I have new 4116s in bank 0 but that's not to say none are faulty. My Super 80 has very bad sockets that I've been gradualy replacing. I think I may have found the problem, U75 74LS139 is in a bad socket, the pins are giving suspicious signals, weak and sometimes non existant depending on how much pressure I exert on the pins. After pushing it a little I've had several minutes of stable behavious, no random characters while pushing down on it. Once I release pressure it takes several minutes for random characters to slowly appear. I'll resocket the chip over the next couple of days.

 

Next problem: I found a dry join on the CAS signal line resistor, no conntinuity to RAM bank1, I fixed that so now I have 32K RAM. I've filled bank 2 but suspect it's got some bad chips (old ones) as the Super 80 won't boot with the switches set to 48K RAM. I'll get to that one eventually.

 

I've also cobbled up an EPROM version of the 2513 Char Gen ROM. I'm still missing the last dot on every char line with this in place of the new 2513 so I am confident that the 2513 is good and I haven't damaged it. This leads me to believe that the 74LS165 (U23) could be the problem.

 

 

Peter.

[Robert]

You can use your Super-80 to help you identify bad ram.

 

First way:

Type in E0

Type in C7. (note that the full stop is required)

Type in G0

After about 5 secs, press the reset button.

Now use the H command to examine memory, it should be filled with 0 and 1.

Check out the 48k region with H8000

When you ran this little program, your screen may have filled with @A@A characters.

You can display other memory pages in the same way by entering O F1 xx, for example, O F1 80

Press key to get back to normal.

 

If this doesn't help, type in the program below which will fill memory with 55 and AA and reboot the computer.

 

Type in E0

Type in 21 0 1 36 55 23 36 AA 2C 20 F8 24 7C FE C0 20 F2 C3 0 C0. (don't forget the full stop)

Type in G0

After a moment, your screen will fill with UJUJ characters and then reboot.

Then you use the Hxxxx or O F1 xx commands to examine the results.

 

You might be able to determine a pattern of corrupt bits, and then be able to identify a faulty chip. Then, swap the chip with a good one and see if the fault moves (faulty chip) or stays (faulty socket).

[Peter]

You can use your Super-80 to help you identify bad ram.

 

I've just tried out those methods you suggest and there does seem to be a problem. Initially the odd memory location has the wrong value (not 0 or 1). Above 8000h the memory looks really bad, nothing consistant.

 

I typed in the program and executed it then rebooted and examined pages starting from 0000h and there appears to be lots of inconsistancies there too. Anyway I'll replace the entire row of sockets at bank 0. and do some more testing. The memory corruption is more evident in the first 16K of RAM. The next 16 are more stable and I can type in commands etc. without the thing becoming unusable. Still it won't boot with switches set to 48KRam.

[Robert]

I forgot to mention that with the program, it doesn't touch the memory between 0-FF otherwise it would overwrite itself.