1200XL Clearpic 2002 Issue

[+Larry]

I've just finished (and re-checked) Clearpic 2002 for the 1200XL as posted at www.retrobits.net. But I get no chroma, after connecting the unused pin on the monitor jack (J2-5). But I get great composite color. As I said, I've rechecked the components, and perhaps I have a bad solder connection, but I can't find it thus far.

 

Before I start ripping components out and replacing them, I thought I'd check and see if anyone else has successfully completed this mod as posted. I couldn't find it posted anywhere else to cross-check against a possible typo/error. Perhaps someone has it posted elsewhere or a file?

 

Thanks,

Larry

[walter_J64bit]

I've just finished (and re-checked) Clearpic 2002 for the 1200XL as posted at www.retrobits.net. But I get no chroma, after connecting the unused pin on the monitor jack (J2-5). But I get great composite color. As I said, I've rechecked the components, and perhaps I have a bad solder connection, but I can't find it thus far.

 

Before I start ripping components out and replacing them, I thought I'd check and see if anyone else has successfully completed this mod as posted. I couldn't find it posted anywhere else to cross-check against a possible typo/error. Perhaps someone has it posted elsewhere or a file?

 

Thanks,

Larry

Try here!

[+Larry]

Hi Walter-

 

Thanks, but this looks to be an earlier (different) version. AFAIK, there have been 3 Clearpic mods:

Clearpic

Clearpic 2

Clearpic 2002.

 

These were all somewhat different. But I appreciate the post, and if push comes to shove, I'll rip out the 2002 and try the earlier one.

 

-Larry

[charliecron]

I know I just ran a wire from the top hole of R27 to the solder points for the monitor jack on the bottom of the board. Works great.

[+Larry]

I know I just ran a wire from the top hole of R27 to the solder points for the monitor jack on the bottom of the board. Works great.

 

Hi Charlie-

 

Thanks for the reply. I presume you used the version of this mod as posted at retrobits.net?

 

And just for clarification, you attached the jumper wire from the top hole of R27 (now empty) to the un-connected monitor pin (no trace to it)?

 

-Larry

[charliecron]

I know I just ran a wire from the top hole of R27 to the solder points for the monitor jack on the bottom of the board. Works great.

 

Hi Charlie-

 

Thanks for the reply. I presume you used the version of this mod as posted at retrobits.net?

 

And just for clarification, you attached the jumper wire from the top hole of R27 (now empty) to the un-connected monitor pin (no trace to it)?

 

-Larry

 

Hi Larry,

 

Yes, I did the mod at retrobits, And yes, top R27 (now empty) to the unconnected monitor pin with no trace.

 

Charlie

[+Larry]

Thanks, Charlie. It must be my error, somehow...

 

-Larry

[charliecron]

If you've got great composite, I would guess that it has to be that wire.

[walter_J64bit]

WOW, I have to get this one a try as soon I get my 1200Xl back in working order! with other mods for 1200XL I'm looking to do!

[gcude]

WOW, I have to get this one a try as soon I get my 1200Xl back in working order! with other mods for 1200XL I'm looking to do!

I did this exact mod a while back and only hitch I had was wrong resistor value (my bad) on one piece. Once I put in the right resistor, my 1200XL had awesome video.

[+Larry]

I've found a couple of related schematics that should help me track down the problem, but perhaps someone can answer a couple of related questions.

 

1) Is the Chroma output from GTIA predominately one pin (26?). If that is the case, I can trace through the schematic to only those changes made on that "leg" of the mod. By the same reasoning, anything related to composite must be fine.

 

2) I used hookup wire -- probably 30 gauge -- to connect the Chroma to the monitor jack. I looked at the other traces, and they were very small, so I thought the hookup wire would be fine. Could that be an issue?

 

-Larry

[classics]

1) Is the Chroma output from GTIA predominately one pin (26?). If that is the case, I can trace through the schematic to only those changes made on that "leg" of the mod. By the same reasoning, anything related to composite must be fine.

 

Chroma is on pin 21 of GTIA. You can pick up the amplified chroma output at R45.

 

2) I used hookup wire -- probably 30 gauge -- to connect the Chroma to the monitor jack. I looked at the other traces, and they were very small, so I thought the hookup wire would be fine. Could that be an issue?

 

It shouldn't, though with unshielded wire you will have to be careful how you route it, or you will pick up bars in the luma.

 

Steve

[Urchlay]

It shouldn't, though with unshielded wire you will have to be careful how you route it, or you will pick up bars in the luma.

 

*That* explains what's wrong with my clearpic upgrade... I can fix the annoying bars by taking the Atari apart and moving the chroma wire a bit, but over time it seems to move back to its original position... I used non-stranded wire (because I have a ton of it), and I guess it's acting like a spring.

 

If I want to replace it with shielded wire, I guess the shield needs to be connected to a nearby ground on either end?

[classics]

If I want to replace it with shielded wire, I guess the shield needs to be connected to a nearby ground on either end?

 

Yes, but luckily the other side of R45 is ground.

 

Steve

[Urchlay]

If I want to replace it with shielded wire, I guess the shield needs to be connected to a nearby ground on either end?

 

Yes, but luckily the other side of R45 is ground.

 

It doesn't need to be thick gold-plated "monster" shielded cable or anything, does it?

 

Actually... what about twisted pair? I have about a mile of Ethernet cable here... would it work better to connect both wires in a twisted pair to the chroma signal, or one to ground and the other to chroma?

Edited May 14, 2007 by Urchlay

[classics]

It doesn't need to be thick gold-plated "monster" shielded cable or anything, does it?

 

No, the last time I used a shielded wire it was from an old wireless router antenna. Very thin and it worked great.

 

You might also be able to just use unshielded wire and get away with it. Just route it carefully to the large ground strip at the edge of the board, then just run it along that over to the monitor jack.

 

Steve

[+kheller2]

The ClearPic Modification at Curt's site is a modification to the original ClearPic. I've never heard of clearpic 2 or 2002. I do have the original ClearPic instructions if anyone wants to see them.

[Beetle]

Look here:

 

 

Here is the original Clearpic

Here is the Clearpic2002

 

Have fun,

Beetle

[walter_J64bit]

I've just installed the ClearPic mod the older one but now my 1200XL has the Rambo XL, ClearPic and the 5v output mod! Now I need the 800XL OS ROM and MMU Mod! This is fun!

[+Larry]

1) Is the Chroma output from GTIA predominately one pin (26?). If that is the case, I can trace through the schematic to only those changes made on that "leg" of the mod. By the same reasoning, anything related to composite must be fine.

 

Chroma is on pin 21 of GTIA. You can pick up the amplified chroma output at R45.

 

2) I used hookup wire -- probably 30 gauge -- to connect the Chroma to the monitor jack. I looked at the other traces, and they were very small, so I thought the hookup wire would be fine. Could that be an issue?

 

It shouldn't, though with unshielded wire you will have to be careful how you route it, or you will pick up bars in the luma.

 

Steve

 

Hi Steve-

 

I rechecked the components and solder connections yet again, and still Chroma-a-no-go at the R27 position. Then I connected the wire to the Chroma pin on the jack to R45 and the Chroma came right up -- looks beautiful! Do you (or anyone else) have a theory as to why this might be? Looking at the partial schematic (from CLRPIC2, C. Dyson's drawing) GTIA pin 21 goes to Q11. The output of Q11 goes to R22 (removed in the mod) which goes on to R27 (also removed in the mod). The R27 connection should work because it is connected to C61 (and I did connect the wire to the correct side of R27).

 

But at any rate, R45 works great.

 

-Larry

[classics]

Do you (or anyone else) have a theory as to why this might be? Looking at the partial schematic (from CLRPIC2, C. Dyson's drawing) GTIA pin 21 goes to Q11. The output of Q11 goes to R22 (removed in the mod) which goes on to R27 (also removed in the mod). The R27 connection should work because it is connected to C61 (and I did connect the wire to the correct side of R27).

 

Q11 is the luma driver, its output is then mixed with the chroma for composite and also sent to the RF modulator.

 

Q7 is the last chroma driver. Its tapped off at C61 and through R27 for mixing with the Luma signal.

 

You could try replacing C61 with a larger capacitor like a 0.1uf. But I think it would be best just DC coupling the chroma signal by getting it at R45.

 

Steve

[+Larry]

Hi Steve-

Thanks much for solving this for me!!!

-Larry

[+Guitarman]

I've just installed the ClearPic mod the older one but now my 1200XL has the Rambo XL, ClearPic and the 5v output mod! Now I need the 800XL OS ROM and MMU Mod! This is fun!

 

 

Don't forget adding internal Basic RevC with that XL OS upgrade!!

[+kheller2]

Look here:

 

 

Here is the original Clearpic

Here is the Clearpic2002

 

Have fun,

Beetle

 

Beetle, I'm not sure you are correct about that being the original ClearPic. It states "the sequel to the CLRPIC modification is much "better" than the original."

 

Here is the original off an old Woolley floppy:

CLEARPIC

 

 

If I were allowed only one computer, I think that I would prefer a 1200XL.

Only two features draw me toward the 800XL or the 130XE, the Parallel Buss and

the quality of the video on my 1702 Commodore. The 130XE makes the 1200XL

screen look like I'm using a television - through the tuner! Oddly enough, the

1200XL has almost a dozen transistors in it's video circuits, while the XE only

has 3 or 4. Yet, the 130XE has a much, much better output. (same transistors,

same signal source.... did the Warner engineers get paid by the component???)

Nice for us, though. We can just duplicate the XE circuitry in the 1200XL -

which is exactly what I will describe in this article. The result is a picture

that is just as clear as the one from a 130XE and costs almost nothing. This is

designed for a separate CHROMA system like the 1702. There is no provision for

output to a television or a composite monitor.

Installation will consist of removing certain components and either

replacing them with another part, replacing them with a wire, or not replacing

them at all. One component has to be added at a point in the circuitry where no

component now exists. All others are mounted in existing locations.

 

REMOVE REPLACE WITH

 

R21 22K 1.5K

L15 820uh wire

C115 10uf wire

C60 100pf ----

R187 1meg 2.2K

CR20 1N4148 ----

R22 4.3K ----

R23 180 47

R24 180 100

R25 130 ----

R28 130 wire

C62 10pf ----

R180 180 ----

R181 3.3K 6.8K

C118 100pf wire

R182 6.2K ----

R183 2.2K ----

R184 1K wire

R185 1K 180

C119 3.9pf ----

CR19 1N4148 150ohm resistor

C116 .001uf ----

 

Add a 47ohm resistor between the collector of Q11 and +5volts. You will have to cut the foil right next to the pad to isolate the collector.

 

Solder a wire from the junction of CR19 (now a 150ohm resistor) and R180

(removed) to the unused pin on the monitor socket. This is the new CHROMA

source.

 

Pull out Q7, Q8, Q16, Q17, and Q18.

 

 

Check all of your changes very carefully. Measure the resistance between

+5volts and ground to make sure that you haven't got any power supply faults.

(It should read over 100ohms)

Power up in self-test mode and correct the color by adjusting R48.

 

You are now only missing the Parallel Buss.....

 

Bob Woolley

75126,3446

Edited May 16, 2007 by kheller2

[Urchlay]

I've just installed the ClearPic mod the older one but now my 1200XL has the Rambo XL, ClearPic and the 5v output mod! Now I need the 800XL OS ROM and MMU Mod! This is fun!

 

 

Don't forget adding internal Basic RevC with that XL OS upgrade!!

 

If you do that, you might also want to use the "reverse BASIC" patched XL OS, so your 1200XL still acts like a 1200XL when there's no cartridge. The reverse BASIC OS defaults to disabling BASIC, and only enables it if you hold down OPTION at power-up. Unless you're actually programming in BASIC a lot, this is a lot nicer than the regular 800XL OS (it gets old having to hold down OPTION 99% of the time).

 

Of course, the deluxe version of this is to use the 32-in-1 OS upgrade, from Atarimax. Your 1200XL can become an 800 or an 800XL any time you want, without having to load any translator disks (and the reverse-BASIC OS is selectable as one of the 32 choices).