dukes909

What type of monitor are connecting it to? My 2005 Gateway LCD with S-video input died today and I sm looking for a replacement. Dukester

Thanks, that looks to be UK; I am in the states. I may check out auto parts store to see if they have anything close enough in size. Dukester

I think that is what these are called? Any source for these? I have misplaced a couple in the process of disassembly. They appear to be slightly less than 5/32" diameter and no longer than 1/4" when center pin is flush with concave part. Dukester

This is the culprit! Not an electrolytic. Not sure what this style is called but it was way out of spec and conducted voltage right on through when applied. Thanks for the help and follow-up! Dukester

That's what it was. Great job!

Thanks! It must be in this area but I cannot figure out what it is. On the working board, I get 5V on one side of R156 (my schematic) and 3.65V on the other side (which I think is correct if I calculated voltage drop correctly) and 3.65 at pin 3 of the CD4050 (A103). I also show 470K resistance across R156 in circuit in the working board. On the non-working board, I get 5V on one side of R156 and 0V on the other side, and 0V at pin 3 of CD4050. It shows 100k resistance across R156 while the resistor is in circuit. I unsoldered it and checked it out of circuit and it shows 470k like it it is supposed to. Aaargghhhh....where is it?!

Ok, is this from an Atari 800 schematic? What is A111F? This doesn't look like the schematic from the post yesterday unless I am totally missing where this is. Mine looks like this:

Guys, I have an Atari 800 motherboard that is causing me grief. The symptoms are a solid green screen when the 800 is powered on, no keyclicks. Star Raiders cartridge does not do anything (green screen). No Memo Pad screen without cartridges. Things I have tried: - Checked voltages on power supply board: 7805, 7812, J201/J115 connector. I have 12V, 5V, and -5V there, but see note in "Weird things" below about this. - Swapped CPU board with known good one - Swapped ROM board with known good one - Swapped RAM board with known good one - Swapped power supply board with known good one - Swapped every IC on motherboard with known good ones I have done these individually and as a whole with the same result. Additionally, I have: - Taken CPU board from this non-working 800 and put in a working 800 and that working 800 still works - Taken ROM board from this non-working 800 and put in a working 800 and that working 800 still works - Taken RAM board from this non-working 800 and put in a working 800 and that working 800 still works - Taken power supply board from this non-working 800 and put in a working 800 and that working 800 still works - Taken chips off of non-working 800 and put them in a working 800 and that working 800 still works At this point I think I can safely (?) say it is on the motherboard and not any of the daughterboards (RAM/ROM/CPU). I verified the oscillator is producing a good, correct clock signal that is getting to CPU. Transistors on motherboard show same readings on non-working board vs working board. Weird things I see on the non-working 800: - Low voltage on pin 10 of the connector J201/J115 ( 0V on non-working board vs 5V on working board). (marked DATA OUT and SOD on schematic). All other J201/J115 pin voltages match exactly. - Low voltage on pin 25 of motherboard CPU card connector J101 (RESET) (0V on non-working board vs 5V on working board). Additionally I see SEVERAL other (26 out of 56) low voltage readings on many of the CPU connectors on J101, and 4 of the 56 on the non-working board are high compared to the working one. I can only guess there is a short somewhere, or possibly a gate, or a combination thereof. However, I am not sure how it could be a gate when the same chips work in another 800 motherboard. Any ideas for tracking down the cause further?? Cheers Dukester

Pin 3 on the regulator. It is the output pin and where I would have expected to (and have in all other use cases until now) see 5V on the 7805 and 12V on the 7812..

For the 7805 and 7812 regulators on the 800 PS board, I do not get 5V and 12V on pin 3 of these unless the PS board is connected to the motherboard via J201/J115. Is this normal? If so I am not clear how that works; is a load needed to get the proper output voltage which would be something new to me. Cheers, Dukester

The one @kheller2 posted is quite readable!

Thank you!

Hey gang, I am looking for a more legible copy of the Atari 800 service manual ( from AtariMania ), page 2-10 in the manual, page 50 in the PDF file. It's difficult to read the CPU J101 / Test Point lines. Anyone have a better copy? Cheers Dukester

Thanks -I sort of remember the Wico from electronic games magazine way back when. Not familiar with the CX78 but i will look it up. Dukester

Though I really like the classic joysticks that came with the VCS, arthritis in my hand has made the base of those uncomfortable to use for any length of time. Is there a readily available joystick for these systems that has a base that is easier to hold for old guys like me (one that is maybe not so wide)? Cheers Dukester

Do you mean other than the SN7407 mentioned in the article(whihch I am using)?

Instead of a relay I have an LED hooked up with a 220ohm resistor. Toggling back and forth between input and output on PORTA and sending 0 and 1 to the same port does nothing. Doing the same thing on PORTB lights the LED on & off. I double checked the program to make sure everything was correct.

Cool. I am curious as to how it all worked. Do you still have the software and schematic?

Oof, you're right - I missed that as I skipped over the logic probe diagram a little too far. Even if I had caught it, it wouldn't have explained why PORTA didn't work (hence my post and subsequent answer here), all other things being the same. Actually, ports 1 & 2 still don't work even after toggling back and forth several times but I am making do with the same circuit connected to PORTB for now. Cheerio

To that end after getting it working on PORTB I cycled PORTA several times without success. (Several!). Huh.

Well I'll be darned. I changed to PORTB and it works like a charm. Thanks for this info!

Hey folks, I was goofing around on a rainy Saturday with my 800 and thought I would try this old article of using the joystick ports for input / output to control an LED: Interfacing your Atari When I couldn't get this to work I backed up and checked the pins on my 800 joystick port 1 with a DVM. As it is I am reading +5V on pins 1-4 all the time (in fact there is +5V on each of ports 1-4 pins 1-4 all the time). Am I missing something obvious here as I thought only pin 6 is supposed to be +5V? Running the program on the aforementioned website made no changes to the pin readings when in output mode, regardless of value 1 or 0. The joystick port works fine for games so I am not clear what is going on. Cheers Dukester

Guys, I bought one of these in a weak moment. The first time I connected the composite cables to my4 4-way AV RCA Switcher I got a black and white picture on the TV. Powered the Frogger unit on & off and then it came up in color and worked great. The next 100 or so times I tried powering it on & off I am back to black and white. Hooking the unit up directly to the TV I get the same results. Occasionally, the game shows a bar across the top of the screen in a purplish hue but the rest of the screen is B&W. Is this just a bad unit or is there anything else I can test inside the thing? All my other other standalone units (Jakks) display color fine on this same TV and connected through the switcher. Cheers

So in this thread I was helped by the folks here to learn that one of the voltage regulators on my 800 power supply board was bad. On that same board there appears to be corrosion on some of the solder joints: and it looks like the corrosion spills over multiple traces. Does this need to be cleaned off, and if so, how? Yes I am new to this. Cheers Dukester

Yes reviving an old thread but I bought a wonky A800 a few months ago. Mitsumi keyboard, & only 2 keys worked, maybe, kinda sorta. Found this thread, watched the flashjazzcat yt video previously mentioned, bought some conductive paint, and wowee zowee every key works again! Thanks folks! Now I just need some memory for the poor things and a 6532 chip for my dead 810 drive. One step at a time! Thanks again Dukester