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Atari 1050

JammyJules

JammyJules

Experienced Member
Joined
Oct 27, 2025
Messages
159
Location
Wales
Evening all!

I lucky enough recently to pick up an Atari 800XL with a 1050 floppy.

The 800XL booted straight into the RAM test and failed. I diagnosed two of the memory chips and replaced them - it passes all tests now - great 👍

The 1050 powered on with a the red light, but didnt make any homing sounds, and trying to access gave error 130. I tested the "buzzing" power supply I had with it and it appears to be outputting 17 DC. So I dont know if that has damaged anything. Certainly not seeing 12v anywhere on the board.

Anyway, as new AC 9v power supplies seem to be getting rare, I did the DC conversation. I now get 5v and 12v from the voltage regulators, but the drive still doesn't move. I am now powering it from a bench supply - 12v 3 amps.

I got my scope out, and noticed D0 on the 6507 sometimes had activity (mostly not) when turning on and off. If it did, it would keep running. But when reconnecting the drive, it doesn't init again. I cannot check D0 while the drive is connected, so I am assuming I just didnt get a working "boot".

Scoping the reset line on the 6507, it is instantly going high. I did see a small delay once, and this is when D0 seemed to show activity.

Am I right in assuming there should be a short delay in the reset like other computer based systems?

The clock seems to be good on all occasions running at ~1mhz (in and out of the 6507).

Any advice would be greatly appreciated.
 
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Normally there is no D: device until DOS is loaded. That's why you get error 130. So if the 1050 is your only storage device, you'll need a bootable floppy to use it. With the drive powered on first, when you switch the computer on it should try to boot. If the drive is detected on the SIO port, but doesn't contain a bootable disk, I recall that the computer would make a 'raspberry' sound (on the TV speaker) for a few seconds before timing out.
 
I have discs. Nothing happens when I boot with one in.

The power light is on but the drive light doesn't illuminate.

I have seen o YouTube if you power the drive even disconnected from the computer it does have some movement of the head?
 
JammyJules said:
I have discs. Nothing happens when I boot with one in.

The power light is on but the drive light doesn't illuminate.

I have seen o YouTube if you power the drive even disconnected from the computer it does have some movement of the head?
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I'm going to guess drive initialization failure if you haven't already. Could you please send pictures of the drive without the case? This is probably one of the first times I'm doing this so you might want to cross reference anything I say with another source. Also, I'm pretty darn sure you're not supposed to be getting 17v for the 1050.
 
xp0nentz said:
I'm going to guess drive initialization failure if you haven't already. Could you please send pictures of the drive without the case? This is probably one of the first times I'm doing this so you might want to cross reference anything I say with another source. Also, I'm pretty darn sure you're not supposed to be getting 17v for the 1050.
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Thanks for the reply David.

Attached are a few picture of the board. You can see the DC mod quite clearly hopefully. I used this guide :

https://www.ifixit.com/Guide/The+simple+Atari+1050+Disk+Drive+Conversion+to+DC/172455

I have removed the rom and read it ok in my T48 programmer - so I think that is fine.
I scoped the 6507 and found that sometimes it is not executing code, and sometimes it is. When it is running, the CE on the rom is looking healthy. I connected the floppy mech, still scoping the CE on the rom and got it to boot with code running, but the activity light and the drive motor shows no signs of life. If the cpu is running, it will continue to run. So it either starts correctly and runs, or it starts and stops very quicky on power up.
The clock is always ok - if it is frozen or not.

I have checked the large diodes (near the mod) with a MM and they appear to be fine.
I have resoldered all the IC sockets, removed the ic's, cleaned the legs, contact cleaned the sockets.
I have a good 5v and 12v on the test points wne the cpu is running or not (halted).

I have an ESR meter on order, will hopefully be with me tomorrow, so I can check the caps in circuit hopefully.
 

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JammyJules said:
Thanks for the reply David.

Attached are a few picture of the board. You can see the DC mod quite clearly hopefully. I used this guide :

https://www.ifixit.com/Guide/The+simple+Atari+1050+Disk+Drive+Conversion+to+DC/172455

I have removed the rom and read it ok in my T48 programmer - so I think that is fine.
I scoped the 6507 and found that sometimes it is not executing code, and sometimes it is. When it is running, the CE on the rom is looking healthy. I connected the floppy mech, still scoping the CE on the rom and got it to boot with code running, but the activity light and the drive motor shows no signs of life. If the cpu is running, it will continue to run. So it either starts correctly and runs, or it starts and stops very quicky on power up.
The clock is always ok - if it is frozen or not.

I have checked the large diodes (near the mod) with a MM and they appear to be fine.
I have resoldered all the IC sockets, removed the ic's, cleaned the legs, contact cleaned the sockets.
I have a good 5v and 12v on the test points wne the cpu is running or not (halted).

I have an ESR meter on order, will hopefully be with me tomorrow, so I can check the caps in circuit hopefully.
Click to expand...
Hi, glad you checked the ROM. Check a few caps until your ESR meter arrives. Is it still giving 17v? Also try to check and see if anything is shorted.
 
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Watched a video about the 1050, the guy said something about resoldering the connectors that get physical stress and reseating some of the ICs.
 
xp0nentz said:
Hi, glad you checked the ROM. Check a few caps until your ESR meter arrives. Is it still giving 17v? Also try to check and see if anything is shorted.
Click to expand...
I am not using the power brick that came with it - i am using a bench supply 12v 3amp
 
I dont think I have a short, as I have 5v and 12v on the test points outlined by the service manual.
 
xp0nentz said:
Watched a video about the 1050, the guy said something about resoldering the connectors that get physical stress and reseating some of the ICs.
Click to expand...
I have done the IC's , not sure what solder joints would get stressed. I have watched a few videos too - everyone I've seen they fix a short or change a regulator and it comes back to life.

I was assured by the seller it worked "last time he used it". He seems like a reasonable guy, was a collector himself.

Im tempted to reflow every joint.
 
JammyJules said:
I have done the IC's , not sure what solder joints would get stressed. I have watched a few videos too - everyone I've seen they fix a short or change a regulator and it comes back to life.

I was assured by the seller it worked "last time he used it". He seems like a reasonable guy, was a collector himself.

Im tempted to reflow every joint.
Click to expand...
Try reflowing every joint, check for a few shorts if possible since this kinda sounds like a short. Check the big capacitors maybe.
 
Inspect the board a bit to see if anything doesn't look right. That could very well be your issue.
 
It was shipped. I have done a visual inspection- i have starred at this board for hours now lol.

Today a replaced all the small electrolytic caps - seems to be worse now. Where as before I could sometimes get activity on the CE of the rom, now there its just high all the time.

I started this repair hobby as a challenge - certainly got one now 😆
 
I find this interesting and frustrating :

I removed a 47uf 16v cap, and I have 3 ways to test it.

1. Owon SPM6103 bench supply and multi meter reads : 58.13uf
2. TC1 Multi-function tester reads : 50.23uf, ESR 2.9 ohms
3. PEAK atlas ESR70 gold meter reads : 48.67uf, ESR 2.6 ohms

I wonder which is correct ?
 
JammyJules said:
It was shipped. I have done a visual inspection- i have starred at this board for hours now lol.

Today a replaced all the small electrolytic caps - seems to be worse now. Where as before I could sometimes get activity on the CE of the rom, now there its just high all the time.

I started this repair hobby as a challenge - certainly got one now 😆
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That's strange. Also this is one of my first times helping in a repair so everything I say please try to double check, if we cannot get the drive up and running I apologize in advance. Also, maybe shipping damaged it? If we can't repair it, then I think eBay has a few of them.
 
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JammyJules said:
It was shipped. I have done a visual inspection- i have starred at this board for hours now lol.

Today a replaced all the small electrolytic caps - seems to be worse now. Where as before I could sometimes get activity on the CE of the rom, now there its just high all the time.

I started this repair hobby as a challenge - certainly got one now 😆
Click to expand...
Can you send a few pictures of the scopes? Also, maybe theres a slim chance of some of the issues being related to the computer.
 
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xp0nentz said:
Can you send a few pictures of the scopes? Also, maybe theres a slim chance of some of the issues being related to the computer.
Click to expand...
There is definitely something wrong with the computer, as the chip enable line is staying high on the rom. I will burn a new one later, although I can read the original.
 
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