What original chips for the XL/XE are in short supply?

[TGB1718]

16 hours ago, manterola said:

delay line chips are also scarce.

I've seen a few threads posted here about the delay line chip, do we have any details on the delays themselves ?

 

Just wondering if this chip could be used instead 

 

https://www.ti.com/lit/ds/symlink/sn74ls31.pdf?ts=1592740711549&ref_url=https%3A%2F%2Fen.wikipedia.org%2F

 

 

[Rybags]

Fairly sure the main use is the Ras to Cas delay which should equate to a little under half a machine cycle.

 

At 1.79 MHz a machine cycle = about 558 ns.

By the looks, the linked chip is about 6 times too fast.

[TGB1718]

18 minutes ago, Rybags said:

By the looks, the linked chip is about 6 times too fast

it does say you can use them in cascade, so a single chip if wired outputs to inputs would give ~154ns

 

so would need 4 chips mounted on a small board, shame really, back to the drawing board ?

 

[Rybags]

Likely there's slower ones available.

If there's too much complexity in a replacement then the better option would probably be to just make a modern day Freddie, then replace the main crystal with the 14 MHz part, then feed back the 3.59 Mhz from the divided down clock and also provide the relevant Ras/Cas delay.  Though just how much hacking about that would require... ?

[Tickled_Pink]

What does a delay line actually do and why is it needed?

[thorfdbg]

3 minutes ago, Tickled_Pink said:

What does a delay line actually do and why is it needed?

As the name suggests, it delays a signal by a given amount of time (a couple of nanoseconds). It is used in the XL series to generate the CAS and RAS signals for the RAM chips. Even though each chip contains 64Kbits, it does not have 16 address pins to address each bit, but only 8 address bits. You first supply the row address, then the column address, as the RAM forms a 2d matrix. The delay between the row and column address is generated by the delay line. These are electro-accoustic modules, i.e. "mechanical" in a sense and thus can die of old age.

 

[+Larry]

bfollowell said:

"I'd like to put a BASIC C in my 800XL, but it came with BASIC B, and I'm not aware of having ever experienced any ill effects. I'm not even 100% certain that I need one. I'm just troubleshooting at this point. Would I be right to assume that there's a CO24947A BASIC C chip in every BASIC C cartridge? Though the thought of sacrificing a cartridge to get at the chip inside kind of goes against my nature. Can we use an EPROM to make our own BASIC C chip? Is that code available for download anywhere?"

 

I have one of those Rev C carts and opened it.  It has a single 2364 Rom -- CO24947A BASIC C chip as you mentioned.  It is 24-pin, so yes, I'd think that you could desolder one from a cart and use it.  My only concern would be that the legs are clipped short in my cartridge, so getting good contact might be an issue. If you have an eprom burner, I'd go the eprom route, or maybe do one of the upgrades like U1MB or Antonia.  They give you a lot of bang for your buck, including multiple OS and multiple languages.  For instance, Altirra BASIC is quite an improvement over even Rev C.  But will cost more money to do the upgrade, too.  I'm sure a BASIC C rom file is widely available, or if you have a Rev C cartridge, you can dump the rom and burn an eprom with the file.  Not difficult, but you do need a 2364 --> 2764 adapter. And don't forget that Altirra Extended BASIC is available if you have an Atarimax 1Mb flash cart.  Lots of choices.

 

 

 

 

 

[bfollowell]

35 minutes ago, Larry said:

bfollowell said:

"I'd like to put a BASIC C in my 800XL, but it came with BASIC B, and I'm not aware of having ever experienced any ill effects. I'm not even 100% certain that I need one. I'm just troubleshooting at this point. Would I be right to assume that there's a CO24947A BASIC C chip in every BASIC C cartridge? Though the thought of sacrificing a cartridge to get at the chip inside kind of goes against my nature. Can we use an EPROM to make our own BASIC C chip? Is that code available for download anywhere?"

 

I have one of those Rev C carts and opened it.  It has a single 2364 Rom -- CO24947A BASIC C chip as you mentioned.  It is 24-pin, so yes, I'd think that you could desolder one from a cart and use it.  My only concern would be that the legs are clipped short in my cartridge, so getting good contact might be an issue. If you have an eprom burner, I'd go the eprom route, or maybe do one of the upgrades like U1MB or Antonia.  They give you a lot of bang for your buck, including multiple OS and multiple languages.  For instance, Altirra BASIC is quite an improvement over even Rev C.  But will cost more money to do the upgrade, too.  I'm sure a BASIC C rom file is widely available, or if you have a Rev C cartridge, you can dump the rom and burn an eprom with the file.  Not difficult, but you do need a 2364 --> 2764 adapter. And don't forget that Altirra Extended BASIC is available if you have an Atarimax 1Mb flash cart.  Lots of choices.

 

Well, the main reason I wanted the BASIC chip is to help me in troubleshooting my 800XL which now only boots to a green screen. I'm not even certain my original BASIC B chip is bad at this point. SysCheck doesn't help at all. I've swapped all of my socketed chips, which are all of the big 40-pin chips and the memory chips, but everything else is soldered straight to the board. So far, everything I've swapped with other machines check out just fine. I've already ordered replacements for all of the LS logic chips, as well as sockets so that my 800XL will be fully socketed. All that leaves is BASIC, OS ROM, and MMU. Then I'll have everything I need to start swapping chips and trying to narrow down my problem. I don't want to spend $100 on a U1MB until I know I've saved my 800XL, though I may install one and a UAV once I get it going again. I'd planned to sell my 800XL once I got my 1088XEL going well, but I've had this 800XL since it replaced my 800 in about 1986, and I'm just not sure I can part with it.

 

[+DrVenkman]

Just now, bfollowell said:

All that leaves is BASIC, OS ROM, and MMU

If you haven't already, just desolder the BASIC chip and see if the machine boots to the Self-Test screen. If so, your BASIC chip is likely bad. If it doesn't, BASIC is probably not the problem.

[bfollowell]

That was the first one I desoldered and installed a socket on. I'll give it a try when I get a chance.

 

My wife and I have two of our out-of-state grandsons this week and they're wild. We can't take our eyes off of them for a minute. I may get a chance one night after we them tranquilized, I mean, in bed.

 

Any good videos, threads, or links about repairing an 800XL keyboard cable? The adhesive and mylar for the ribbon cable is all coming apart on mine, making all but impossible to reinsert. I have an idea or two but am definitely open to suggestions if there's a best practice.

 

Never mind, I did a Google Advanced search and found at least two good threads here loaded with good information and pictures. I'm trying to decide which may be the best method to undertake.

 

Thanks.

 

Edited June 21, 2020 by bfollowell
Found wwhat I needed

[bfollowell]

9 hours ago, DrVenkman said:

If you haven't already, just desolder the BASIC chip and see if the machine boots to the Self-Test screen. If so, your BASIC chip is likely bad. If it doesn't, BASIC is probably not the problem.

 

I gave it a try, but it made no difference. Still boots to a green screen. The BASIC B chip is definitely bad now though, even if it wasn't before. Pin #1 looked a slight bit rusty at the shoulder, which is odd, because it's never been kept anywhere even the slightest bit damp, and there isn't any rust to speak of anywhere else in the machine, but anyway, pin #1 broke off as I was pulling it out of the new precision socket I'd installed earlier in the week.

 

[Sugarland]

11 hours ago, bfollowell said:

I'd planned to sell my 800XL once I got my 1088XEL going well, but I've had this 800XL since it replaced my 800 in about 1986, and I'm just not sure I can part with it.

If you have any doubt about selling it now, you'll probably regret it later. 

[gilsaluki]

Keep your friend.

[cwilbar]

On 6/20/2020 at 1:20 PM, ivop said:

The arcade people have one of these fail:

 

 

Each blob is a Pokey. If one fails, the board is useless. They use adapter boards that take four of "our" Pokeys. That's why I guess

 

I don't know how many of these Atari produced.  I have one Major Havoc board with one in it.  The other has a Quad Pokey Eliminator PCB and 4 POKEYs.  But as I understand it, not all (at least Major Havoc) boards came with a quad POKEY chip.  At a point Atari switched to the QPE with 4 POKEYs.  It probably was cheaper once they ran out of Quad POKEYs since they were producing so many POKEY chips for so many products.

Major havoc came in two boards.... one that was 'dedicated'  (came in the dedicated cabinets), and a conversion board (of which they had conversion kits for Tempest, Space Duel, and Gravitar I believe).  I believe all the conversion boards came with a QPE and 4 POKEYS.

 

I wouldn't be surprised if that above PCB is a Major Havoc PCB.  The board above is a dedicated board (UR in the s/n indicates that... at least for Major Havoc).  At least one other Atari arcade came used a QP chip.

 

[+Stephen]

Pretty strange alignment on the "blobs".  It's making my OCD really give me a tick.

[ivop]

1 hour ago, Stephen said:

Pretty strange alignment on the "blobs".  It's making my OCD really give me a tick.

Haha, yeah, I wondered about the same thing. Why aren't they properly aligned? Grrrr ?

 

Still, I would like to get my hands on a few broken QPokeys and see what can be done with them. No SIO, but there might be squeezed some sound out of them

 

1 hour ago, cwilbar said:

At a point Atari switched to the QPE with 4 POKEYs.

Does that mean there are true Atari Quad Pokey Eliminator boards?

 

Edited June 22, 2020 by ivop

[Rybags]

Most of the connections would be common.  There's 2 CS which should simplify the select logic.

I guess the staggered mounting is for routing of the bonding wires.  I would also guess that they probably only connect the POT lines to one of the chips.

Though given there's modern day replacements taking the 4 Pokeys the pinout should be well documented (might be identical to a standalone chip)

 

Numbers - Atari's biggest seller was Asteroids with about 70,000 but had discrete sound.  By the mid 1980s they'd moved to better sound hardware, Gauntlet was probably one of the last games to use Pokey and had under 10,000 produced.

Given the use of dual/quads I'd guess there were still probably under 200,000 used in arcades in total.

Edited June 23, 2020 by Rybags

[cwilbar]

3 hours ago, ivop said:

Haha, yeah, I wondered about the same thing. Why aren't they properly aligned? Grrrr ?

 

Still, I would like to get my hands on a few broken QPokeys and see what can be done with them. No SIO, but there might be squeezed some sound out of them

 

Does that mean there are true Atari Quad Pokey Eliminator boards?

 

Yes.  I know that the QPE has been reproduced, as has the Major Havoc PCB (along with others like Quantum).

 

All the ones I have are original Atari PCBs.