Atari 1200XL cannot read 16k carts

[Mark2008]

I finally solved my video snow problem (with a clean power supply on my disk drive - no snow).

I got the colors right (u1mb bios upgrade for ntsc color palette).

 

Machine is getting better.....but another problem has been discovered.

 

the 1200XL does not read any 16k carts.  It does work with 8k carts and also works fine with a side3.

 

I did blow out the cartridge slot and spray it with deoxit, but that did nothing.

 

I am ready with a camera, if I need to photograph anything - anyone got experience with an Atari 1200xl that doesn't read 16k carts that would like to help?

 

FYI, this machine has u1mb and VBXE installed.   

 

Edited April 2, 2022 by Mark2008

[BillC]

1 hour ago, Mark2008 said:

FYI, this machine has u1mb and VBXE installed. 

I recommend checking continuity on the cable from the MMU socket to the U1MB, the OS detects cartridge presence/size using signals RD4/RD5 via this cable.

Edited April 2, 2022 by BillC

[sup8pdct]

S4 is  used to select the lower half of a 16K cart. It also comes from the mmu. 

 R19 and R20 are pull ups for RD5 and RD4.

 

I would test the circuit from plugged in cart to the U1MB on both S4 and RD4.

 

 

 

 

 

Edited April 2, 2022 by sup8pdct
wrong info

[Mark2008]

Thanks so much!

 

Now I know this is going to sound scary - but even though I haven't used a voltmeter in 30 years, that's exactly what I plan to do now.

 

But I am like an infant, and it may be a step by step process.

 

So I am going to start by attempting to do one thing that was recommended, and after that I will try all the things that were recommended.

 

But I need to figure out how to "start".   So. - this RD4 circuit.  I googled for 30 minutes, looking at 1200XL motherboard, I just don't see it.

 

Somewhere from the depths of my mind, I recalled you are supposed to look at service manuals.  I downloaded the 1200XL service manual.  If it says RD4 somewhere, I just don't see it.

 

It's not obvious to me, because this is day 1 for me.....so, don't worry about it not being a task for a noob....I take all risks and responsibility - any help will be appreciated!!

 

so, any link to a diagram that says RD4 on it, and maybe has a big red circle and an arrow?  lol

 

 

Edited April 2, 2022 by Mark2008

[Mark2008]

p.s. I do see the cartridge interface on 1200XL service manual, figure 1-13. 

 

OK finally my eyes see RD4, pin A...it seems

 

if that is right, then to test a circuit, I need to find the other end, in this case on the u1mb...nothing I see with my eyes yet....maybe I download u1mb manual now.

 

Edited April 2, 2022 by Mark2008

[TGB1718]

U1M Plugs into the MMU socket, that's where you should check at pin 7 to Cart Socket Pin A, make sure

the U1M is pushed firmly into the socket (no bent pin etc. )

 

Make sure the pullup is ok too, R20 1K Ohms.

[Wrathchild]

if it works with SIDE3 then do 16K ROM or even XEGS images work mounted on SIDE3 as they'd be using the lower cart bank

[BillC]

2 hours ago, Mark2008 said:

p.s. I do see the cartridge interface on 1200XL service manual, figure 1-13. 

 

OK finally my eyes see RD4, pin A...it seems

 

if that is right, then to test a circuit, I need to find the other end, in this case on the u1mb...nothing I see with my eyes yet....maybe I download u1mb manual now.

 

On the later U1MB there are 2 SMD resistors(R8/R9?) next to the MMU cable socket, these resistors are for the RD4/RD5 signals. 

[ivop]

2 hours ago, Wrathchild said:

if it works with SIDE3 then do 16K ROM or even XEGS images work mounted on SIDE3 as they'd be using the lower cart bank

This. If this works, but external real cartridges don't, there is a problem at the cartridge port or the lines on the PCB.

[Mark2008]

I've got to call this a loss, I was wrong about what I said in my first post, where I thought I was going to get a voltmeter and patiently figure this out.

 

Since that post, I attempted a 5v pbi mod, and I destroyed a few hundred dollars of equipment today.  Entirely unrelated task, but I've decided my earlier exuberance about tracing down this issue, probably needs to be rethought.  I probably only will do more damage, not fix the machine.

 

As I understand it, if it were to correctly run the 16k rom as mounted on side 3, that would indicate a board level connectivity problem. And if it didn't - indicate a different type of problem and yet in both cases requiring a technician and parts.

 

Thank you both.  I had asked for that help, you provided it.  It probably would've worked in most cases - but man, not this dude.

 

Now this is the point where - I'm just having a conversation...lol....sharing a bit of extra detail...I had wanted at one time to have an Atari that worked as an Atari, but also had extra memory, a hard drive, and 80-columns.

 

 

I still have 4 of the 7 attempts I've made over the past 8 years....

 

600XL, ram: 512K, hard drive: Side 3, 80 column:  XEP80II.  Doesn't work, XEP80-II is unreadable.

800XL, ram: Antonia 4mb,   hdd: Side 3, 80 column: Sophia(*software in sdx, but it is clear enough for it).  Doesn't work, cannot read the Side 3.

1200XL, ram: U1MB, hdd: Side 3, 80 column: VBXE.   Has the extras, doesn't work as a real Atari - 16k carts unreadable

130XE, ram: Turbo Freezer, hdd: Side 3, 80 column: VBXE.  Doesn't work VBXE is undetectable.

 

 

So, I've tried having dealers make it - 4 times, making myself twice, and one all external solution.  This has to be a record for failure, lol

 

OK that was a lot of unloading, sorry about that!!!

 

Some cool Atari's will be going up on e-bay soon.

 

 

 

Edited April 3, 2022 by Mark2008

[Rybags]

Can you flash or burn a Basic image onto 16K cart?

 

In that case it would work and you might be able to run some simple diagnostics by software to see what's going on.

Such as ? FRE(0) without Dos loaded - if it's the high 30,000s number that would indicate the system is preferring the Ram over lower half of 16K Rom.

If it's the lower value then possibly the system knows it's 16K Rom but can't read the lower half properly (fill the bottom half of the Rom with zeros or some pattern and see what gets read back)