Wizztronics 256K upgrade for 800XL gone bad

[YoshiMatt]

Okay, so my son and I had a go at the 256K Wizztronics upgrade for the 800XL, from Best Electronics. Sadly, the end result is that the machine doesn't boot up upon powering up (black screen), although when we subsequently hit Reset, it comes up with the READY screen, though short lived... after a few seconds the screen begins to flicker, corrupts. So, something went wrong, maybe we fried a chip. Have to say, not the easiest job, this upgrade. There were a couple of items along the way which weren't totally clear.. just maybe, one of them is the culprit:

 

1) In the instructions, on the Figure 1 drawing, the resistor shown on the board is labeled as 330 Ohm, but in the parts list later in the doc they have a 33 Ohm resistor specified. We assumed 33 Ohm was correct, but it wasn’t supplied, so we unsoldered one from a busted 800XL motherboard. The coding is 'orange-orange-black + gold'. Is that right?

 

2) Our Antic chip was socketed, ver C012296. So, we installed all 5 ICs on the Wizztronics board per instructions, then ran a wire from terminal A6 to Antic’s Pin #8, as shown. However, it wasn’t clear if that pin should remain socketed or lifted (like the 5 pins we wired on the PIA)?

 

Thoughts, anyone? Thanks!

Edited December 19, 2010 by YoshiMatt

[Rybags]

Antic Pin 8 is /Refresh.

 

I would say most likely that pin should go into it's socket.

 

What does the 33/330 Ohm resistor sit in between?

[Rybags]

http://www.best-electronics-ca.com/wizztronics_256.htm

 

Also, this page mentions 2 versions of the board, which one you use depends what Antic revision you have.

 

This would be due to the earlier Antic revisions not providing all the necessary Row Addresses required for DRAM Refresh to work properly on large RAM systems.

[YoshiMatt]

http://www.best-electronics-ca.com/wizztronics_256.htm

 

Also, this page mentions 2 versions of the board, which one you use depends what Antic revision you have.

 

This would be due to the earlier Antic revisions not providing all the necessary Row Addresses required for DRAM Refresh to work properly on large RAM systems.

 

Thanks Rybags.

 

The resistor sits on the Wizz board, which has various multiplexer chips.

 

We have the C012296 Antic, so we were following the instructions pertaining to the revision. This is where the Antic pin #8 comes in. It is not supposed to be wired if Antic is C021697.

 

Attaching a phen pic of the final 'product' (sorry, not the greatest quality image)

[Rybags]

The existing RAM is still used, but from the schematics it appears /REF doesn't play part in the onboard memory Refresh if I'm reading them right.

 

Surely other people have this upgrade, so maybe someone else can step in.

 

Also, that resistor value might well play part in the problem if it's the wrong one.

 

 

Additional to all that, the expanded memory shouldn't come into play unless software's running that specifically needs it.

The standard system and OS doesn't know or care about it, so even if it was faulty it shouldn't affect things, unless it was faulty to the point where it was just spitting out random data in an unsolicited fashion.

 

That Best page - if you magnify the pic, the resistor there appears orange, orange, black, gold (assuming it's the same one).

Edited December 19, 2010 by Rybags

[erazmus]

I recently installed this kit in my 800XL. I originally tried a 330 ohm resistor as the instructions seemed to indicate, but it didn't work - black screen. I put in a 33 ohm resistor (orange orange black gold) and it works perfectly.

 

Mine only needed the three chips on the wizztronics board, and didn't need the Antic lead, so I can't confirm whether the pin should remain socketed or be lifted.

 

I built my board with sockets for the chips just in case something failed during the upgrade.

 

From your picture, everything looks correct. The wires from the PIA to the board are in the correct order. The wire over to R32 is in the correct place. Have you double checked the soldering on your board to make sure there's no shorts between any of the pins? There's no solder mask on this board so it's easy to get solder bridges.

 

Can you check the new RAM chips and make sure they're all seated correctly without any pins bent underneath the chip? Are you running this with the metal shield back in place, or without it? I've left the shield off mine since the upgrade without any problems.

[YoshiMatt]

Thanks erazmus. Yes, I may backtrack through everything.. maybe there's a short somewhere on the Wizz board. Or maybe we damaged the PIA during soldering of the pins. Bummer, but at least Best Elec still sells replacement motherboards, if everything else fails..

[sloopy]

also there are people around who repair such stuff too...

 

 

sloopy.

[+Larry]

Hey erazmus-

How about posting a pic or two of your installed Wiz. upgrade. I've got a couple of those and I'm getting an itch to have a go at one.

I have the same board(s) as you. My 2011 resolution is to install some of this stuff I've bought and is still in my parts box!

-Larry

 

I recently installed this kit in my 800XL. I originally tried a 330 ohm resistor as the instructions seemed to indicate, but it didn't work - black screen. I put in a 33 ohm resistor (orange orange black gold) and it works perfectly.

 

Mine only needed the three chips on the wizztronics board, and didn't need the Antic lead, so I can't confirm whether the pin should remain socketed or be lifted.

 

I built my board with sockets for the chips just in case something failed during the upgrade.

 

From your picture, everything looks correct. The wires from the PIA to the board are in the correct order. The wire over to R32 is in the correct place. Have you double checked the soldering on your board to make sure there's no shorts between any of the pins? There's no solder mask on this board so it's easy to get solder bridges.

 

Can you check the new RAM chips and make sure they're all seated correctly without any pins bent underneath the chip? Are you running this with the metal shield back in place, or without it? I've left the shield off mine since the upgrade without any problems.

[Marius]

The chance that you damaged something is really not THAT big.

 

The weakest parts are the RAM chips, and I really don't think these are broke.

 

You wrote you sometimes got READY sometimes, nothing. When the computer is really broke, never ready appears.

 

So keep looking!

Marius

[erazmus]

Hey erazmus-

How about posting a pic or two of your installed Wiz. upgrade. I've got a couple of those and I'm getting an itch to have a go at one.

I have the same board(s) as you. My 2011 resolution is to install some of this stuff I've bought and is still in my parts box!

-Larry

Attached are pictures of my upgrade, in case anyone finds them useful.

[+Larry]

Thanks for the excellent pics! And looks like a very nice installation, too.

-Larry

 

Attached are pictures of my upgrade, in case anyone finds them useful.

[Mclaneinc]

Unless you were not ground then the mem chips could have suffered but unlikely.

 

Sounds like a dry joint if you do get ready sometimes.

[mimo]

I would go over all your soldering again, and give the pcb a bit of a clean to get rid of some of that stray flux

[MEtalGuy66]

I dont see a problem with your soldering. Ive seen much worse work just fine. The flux is nonconductive and shouldnt matter, but if you want to clean it off, just get some acetone (nail polish remover) and a tooth brush. It will take it right off and wont hurt the fiberglass board. Be careful not to get it on anything plastic or painted though..

 

What you can not see though, is what's uder the chip sockets on the top side. That board has no soldermask. Its exremeley easy to create "solder bridges" on boards like that. And if you flowed a little too much solder onto a couple of the joints when installing those sockets, a bridge could have very easily formed between two joints, underneath one of the sockets.

Edited December 21, 2010 by MEtalGuy66

[+Stephen]

I dont see a problem with your soldering. Ive seen much worse work just fine. The flux is nonconductive and shouldnt matter, but if you want to clean it off, just get some acetone (nail polish remover) and a tooth brush. It will take it right off and wont hurt the fiberglass board. Be careful not to get it on anything plastic or painted though..

 

What you can not see though, is what's uder the chip sockets on the top side. That board has no soldermask. Its exremeley easy to create "solder bridges" on boards like that. And if you flowed a little too much solder onto a couple of the joints when installing those sockets, a bridge could have very easily formed between two joints, underneath one of the sockets.

Thanks for the acetone tip - it works great! I used it on the last job I did (desoldered some stuff from my SkunkBoard).

[+Guitarman]

I have 2 systems that I put the Wizztronics upgrade in and they have worked great. They were actually 2 800XL's that had Rambo's installed. I pulled the Rambo's since they can be configed for my 1200XL's and replaced them with the Wizz. The ones I installed were the prebuilt ones though, before Best sold them out. I still have 3 unassembled Wizz kits to use. The good thing is, if you have the board built correctly, you can pretty much use the Rambo installation instruction to install it.

[erazmus]

I dont see a problem with your soldering. Ive seen much worse work just fine. The flux is nonconductive and shouldnt matter, but if you want to clean it off, just get some acetone (nail polish remover) and a tooth brush. It will take it right off and wont hurt the fiberglass board. Be careful not to get it on anything plastic or painted though..

 

What you can not see though, is what's uder the chip sockets on the top side. That board has no soldermask. Its exremeley easy to create "solder bridges" on boards like that. And if you flowed a little too much solder onto a couple of the joints when installing those sockets, a bridge could have very easily formed between two joints, underneath one of the sockets.

Those pictures are of my *working* Wizztronics board, as requested by Larry.

[mimo]

I dont see a problem with your soldering. Ive seen much worse work just fine. The flux is nonconductive and shouldnt matter, but if you want to clean it off, just get some acetone (nail polish remover) and a tooth brush. It will take it right off and wont hurt the fiberglass board. Be careful not to get it on anything plastic or painted though..

 

What you can not see though, is what's uder the chip sockets on the top side. That board has no soldermask. Its exremeley easy to create "solder bridges" on boards like that. And if you flowed a little too much solder onto a couple of the joints when installing those sockets, a bridge could have very easily formed between two joints, underneath one of the sockets.

 

wow, you can tell from that little shot?

http://www.atariage.com/forums/user/27626-yoshimatt/

[ClausB]

I designed the original upgrade 25 years ago and Rambo and Wizztronics based their kits on it.

 

The original BYTE article with 32K banks is posted here.

 

The 16K bank mod that Rambo and Wizztronics copied is here.

 

Yes, it's 33 ohms.

 

A good way to test your 256K RAM chips is to plug them in place of the original RAMs before connecting the circuit board. You would have to tie pin 1 of the RAMs (where the resistor connects) to 5V. Then power up the XL and check that it works normally as a 64K machine. That will check that the new RAMs are functional (but not that all 256K bytes are error-free).

 

Of course, you have already soldered the circuit board in. The original article suggests using a piece of DIP socket to plug onto the PIA pins to lessen the chance of damage to the chip, and to simplify removal of the circuit.

 

Anyway I hope this info helps. Feel free to ask any questions. Good luck.

[sloopy]

I designed the original upgrade 25 years ago and Rambo and Wizztronics based their kits on it.

 

The original BYTE article with 32K banks is posted here.

 

The 16K bank mod that Rambo and Wizztronics copied is here.

 

Yes, it's 33 ohms.

 

A good way to test your 256K RAM chips is to plug them in place of the original RAMs before connecting the circuit board. You would have to tie pin 1 of the RAMs (where the resistor connects) to 5V. Then power up the XL and check that it works normally as a 64K machine. That will check that the new RAMs are functional (but not that all 256K bytes are error-free).

 

Of course, you have already soldered the circuit board in. The original article suggests using a piece of DIP socket to plug onto the PIA pins to lessen the chance of damage to the chip, and to simplify removal of the circuit.

 

Anyway I hope this info helps. Feel free to ask any questions. Good luck.

 

I still have that issue of Byte... i remeber buying it, i was happy cuase atari was mentioned :')

 

 

sloopy.

[ClausB]

I still have that issue of Byte... i remeber buying it, i was happy cuase atari was mentioned :')

 

BYTE did several Atari articles, including installments of "De Re Atari". I was thrilled they put my article in the 10th anniversary issue, at the front of the Homebrewing section even!

 

Did you build the upgrade?

Edited December 22, 2010 by ClausB

[sloopy]

I still have that issue of Byte... i remeber buying it, i was happy cuase atari was mentioned :')

 

BYTE did several Atari articles, including installments of "De Re Atari". I was thrilled they put my article in the 10th anniversary issue, at the front of the Homebrewing section even!

 

Did you build the upgrade?

 

i would have liked to but my first A8 was an 800, not an XL like many people... my next machine was a 130XE, so i didnt get to install on it on there either...

 

but i cant tell you how many C64 friends i would show that to, and tell them that the Atari was a real computer cause it was covered in Byte, and the C64 wasnt :')

 

Ciarcia's 6Mhz wonder there on the front cover was a nice piece, i actually had a friend build one (ordered the pcb from him and then got the parts from jameco, I helped him build it, as his solder skills werent there. It was very cool when we started it up the and monitor showed the startup on my atari terminal :')

 

 

sloopy.

[ClausB]

YoshiMatt,

 

Have you given up on this?