kheller2

Chips and locations 5-11, 5-6.

5 and 12 are on different sio pins.

If your eBay 1050 tests out, you can pull chips out of the bad 1050 and put them into the good 1050 until it fails. Be careful with the ROM/EPROM as there are jumpers that set which is being used. I'm gonna guess the 6810 or the 6532 is bad.

True. But the FDC does provide MotorOn (at least the 1770 and 1772). I guess you could move the head w/o the motor. I'm just surprised at old tech

Looking at that chart... nothing beyond the 400/800 has +12V on the SIO port. So, fully functional is kind of a misnomer. The power supply is 9V AC output. NOT DC. 31 VA All of these devices can use the same power supply: 400,800,810,822,850,1200XL,1010,1020,1050,XF551,PCF554 See section 6.2 of the FAQ: https://mcurrent.name/atari-8-bit/faq.txt

Different, and not a drop in.

On the 1050, precomp is used after track 20, I believe. It’s been a while since we did the source code discussion so I could be misremembering. As for the different FDCs in the XF, I don’t think anyone has posted specifically what rev was used when trying the 1770.

You are failing the power up sequence, section 2-2. The schematics will show you which pins are gnd and vcc per chip. You are probably going to need known good parts to start doing chip swaps. You could also check track zero sensor, but I doubt that’s it.

One of your main chips under the shield has probably failed. https://archive.org/details/1050FSMRebuiltAKH

The only thing I can find about the WD1772-02 vs -00 is “enhanced digital data separation” The XF firmware uses the 6ms step flags so exactly why a 1770-00 doesn’t work at times in a mystery. I wonder if a 1772-00 has the same flakiness. However, the preliminary data sheets show different step tables AND a different rate, 2,3,5,6 vs 6,12,2,3... probably just another typo.... but maybe -00 is different from non -00 and -02. The -02 data sheet also talks automatic pre compensation "The outgoing Write Data stream is delayed or advanced from nominal by 187 nsec [vs the -00 at 125] [and is controlled by some table in the datasheet]." Preliminary: -00 final:

UAV or SV2.1

Awesome.. thanks!

I'm not even sure there was a FSM for this.

Stock 1050s have a long spin time with door closed. Ones that have been modified with a different ROM usually have that cycle much shorter. Everything else sounds like dirty heads, belt or bad disks.

What am I missing? That looks like a normal startup. What are the problems?

So what everyone is saying is we are no better than Atari with a 1450 X3 revision. Could be worse... the 1200 was 13 revisions. Supposedly.

Any symptoms you would care to share with the group?

Any luck on solving this?

Here is a pick of Vandal968's board and yes he did use the NAT chip: And continuing the discussion on W3 vs W4, the 1400 schematics are the same as the 1450 (when it comes to the modem section), but the silk screens on the 1400 use W3/W2 vs W4/W3 on the 1450: I'm amazed anyone could build anything back then following any schematics

I have never seen or heard of an original Atari built board that didn’t use the daughter card. Even the original 1400 prototype boards with little to no silkscreens used the daughter card. Having said that, I don’t know what TONG wound up using onboard (as no one has ever posted hi resolution pictures nor offered to sell one to me). Dynasty boards (all 150 plus prototype 1400) are everywhere compared to TONG. Scarcity goes like this: 1450, 1400, TONG, 130XE in 800XL form. AtariGeezer’s diagram I think is from TONG. There is a whole set done by hand.

Interesting that every drawing has that as W4 going to +12V, including the TONG! It's just semantics -- fix the silkscreen, leave the schematics be. 😁 I find the silkscreen to be wrong most of the time, especially on prototypes. I needed a spreadsheet to track all the duplicated component numbers used on the 128K 800XL board.

Yes it does. And that is tied to pin 15 of the modem board header. That runs through a green resistor looking cap to various other things on the daughter card.

I'll check in a bit, but have you looked at the modem card itself in the pics to make sure it's going to where you think it is? I also have pics of a an original wire soldered perf board from a 1400 board. W3 is also set, but you can see the traces better on the wires.

On my 1450 short board, w3 is jumpered for TI. W4 is open.

AFAIK, all 1200XL keyboards are smooth and semi shiny; the only exception might be the pilot run of units. There are also differences in the color of the letters but I'm not sure if that's from age or when they were manufactured. Someone took a beautiful shot of their 1200XL several years ago that I used as a background image for some time: